GNU Linux-libre 4.19.207-gnu1

[releases.git] / include / linux / fs.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_FS_H
#define _LINUX_FS_H

#include <linux/linkage.h>
#include <linux/wait_bit.h>
#include <linux/kdev_t.h>
#include <linux/dcache.h>
#include <linux/path.h>
#include <linux/stat.h>
#include <linux/cache.h>
#include <linux/list.h>
#include <linux/list_lru.h>
#include <linux/llist.h>
#include <linux/radix-tree.h>
#include <linux/xarray.h>
#include <linux/rbtree.h>
#include <linux/init.h>
#include <linux/pid.h>
#include <linux/bug.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/mm_types.h>
#include <linux/capability.h>
#include <linux/semaphore.h>
#include <linux/fcntl.h>
#include <linux/fiemap.h>
#include <linux/rculist_bl.h>
#include <linux/atomic.h>
#include <linux/shrinker.h>
#include <linux/migrate_mode.h>
#include <linux/uidgid.h>
#include <linux/lockdep.h>
#include <linux/percpu-rwsem.h>
#include <linux/workqueue.h>
#include <linux/delayed_call.h>
#include <linux/uuid.h>
#include <linux/errseq.h>
#include <linux/ioprio.h>

#include <asm/byteorder.h>
#include <uapi/linux/fs.h>

struct backing_dev_info;
struct bdi_writeback;
struct bio;
struct export_operations;
struct hd_geometry;
struct iovec;
struct kiocb;
struct kobject;
struct pipe_inode_info;
struct poll_table_struct;
struct kstatfs;
struct vm_area_struct;
struct vfsmount;
struct cred;
struct swap_info_struct;
struct seq_file;
struct workqueue_struct;
struct iov_iter;
struct fscrypt_info;
struct fscrypt_operations;

extern void __init inode_init(void);
extern void __init inode_init_early(void);
extern void __init files_init(void);
extern void __init files_maxfiles_init(void);

extern struct files_stat_struct files_stat;
extern unsigned long get_max_files(void);
extern unsigned int sysctl_nr_open;
extern struct inodes_stat_t inodes_stat;
extern int leases_enable, lease_break_time;
extern int sysctl_protected_symlinks;
extern int sysctl_protected_hardlinks;
extern int sysctl_protected_fifos;
extern int sysctl_protected_regular;

typedef __kernel_rwf_t rwf_t;

struct buffer_head;
typedef int (get_block_t)(struct inode *inode, sector_t iblock,
                        struct buffer_head *bh_result, int create);
typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
                        ssize_t bytes, void *private);

#define MAY_EXEC                0x00000001
#define MAY_WRITE               0x00000002
#define MAY_READ                0x00000004
#define MAY_APPEND              0x00000008
#define MAY_ACCESS              0x00000010
#define MAY_OPEN                0x00000020
#define MAY_CHDIR               0x00000040
/* called from RCU mode, don't block */
#define MAY_NOT_BLOCK           0x00000080

/*
 * flags in file.f_mode.  Note that FMODE_READ and FMODE_WRITE must correspond
 * to O_WRONLY and O_RDWR via the strange trick in do_dentry_open()
 */

/* file is open for reading */
#define FMODE_READ              ((__force fmode_t)0x1)
/* file is open for writing */
#define FMODE_WRITE             ((__force fmode_t)0x2)
/* file is seekable */
#define FMODE_LSEEK             ((__force fmode_t)0x4)
/* file can be accessed using pread */
#define FMODE_PREAD             ((__force fmode_t)0x8)
/* file can be accessed using pwrite */
#define FMODE_PWRITE            ((__force fmode_t)0x10)
/* File is opened for execution with sys_execve / sys_uselib */
#define FMODE_EXEC              ((__force fmode_t)0x20)
/* File is opened with O_NDELAY (only set for block devices) */
#define FMODE_NDELAY            ((__force fmode_t)0x40)
/* File is opened with O_EXCL (only set for block devices) */
#define FMODE_EXCL              ((__force fmode_t)0x80)
/* File is opened using open(.., 3, ..) and is writeable only for ioctls
   (specialy hack for floppy.c) */
#define FMODE_WRITE_IOCTL       ((__force fmode_t)0x100)
/* 32bit hashes as llseek() offset (for directories) */
#define FMODE_32BITHASH         ((__force fmode_t)0x200)
/* 64bit hashes as llseek() offset (for directories) */
#define FMODE_64BITHASH         ((__force fmode_t)0x400)

/*
 * Don't update ctime and mtime.
 *
 * Currently a special hack for the XFS open_by_handle ioctl, but we'll
 * hopefully graduate it to a proper O_CMTIME flag supported by open(2) soon.
 */
#define FMODE_NOCMTIME          ((__force fmode_t)0x800)

/* Expect random access pattern */
#define FMODE_RANDOM            ((__force fmode_t)0x1000)

/* File is huge (eg. /dev/kmem): treat loff_t as unsigned */
#define FMODE_UNSIGNED_OFFSET   ((__force fmode_t)0x2000)

/* File is opened with O_PATH; almost nothing can be done with it */
#define FMODE_PATH              ((__force fmode_t)0x4000)

/* File needs atomic accesses to f_pos */
#define FMODE_ATOMIC_POS        ((__force fmode_t)0x8000)
/* Write access to underlying fs */
#define FMODE_WRITER            ((__force fmode_t)0x10000)
/* Has read method(s) */
#define FMODE_CAN_READ          ((__force fmode_t)0x20000)
/* Has write method(s) */
#define FMODE_CAN_WRITE         ((__force fmode_t)0x40000)

#define FMODE_OPENED            ((__force fmode_t)0x80000)
#define FMODE_CREATED           ((__force fmode_t)0x100000)

/* File is stream-like */
#define FMODE_STREAM            ((__force fmode_t)0x200000)

/* File was opened by fanotify and shouldn't generate fanotify events */
#define FMODE_NONOTIFY          ((__force fmode_t)0x4000000)

/* File is capable of returning -EAGAIN if I/O will block */
#define FMODE_NOWAIT    ((__force fmode_t)0x8000000)

/* File does not contribute to nr_files count */
#define FMODE_NOACCOUNT ((__force fmode_t)0x20000000)

/*
 * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
 * that indicates that they should check the contents of the iovec are
 * valid, but not check the memory that the iovec elements
 * points too.
 */
#define CHECK_IOVEC_ONLY -1

/*
 * Attribute flags.  These should be or-ed together to figure out what
 * has been changed!
 */
#define ATTR_MODE       (1 << 0)
#define ATTR_UID        (1 << 1)
#define ATTR_GID        (1 << 2)
#define ATTR_SIZE       (1 << 3)
#define ATTR_ATIME      (1 << 4)
#define ATTR_MTIME      (1 << 5)
#define ATTR_CTIME      (1 << 6)
#define ATTR_ATIME_SET  (1 << 7)
#define ATTR_MTIME_SET  (1 << 8)
#define ATTR_FORCE      (1 << 9) /* Not a change, but a change it */
#define ATTR_KILL_SUID  (1 << 11)
#define ATTR_KILL_SGID  (1 << 12)
#define ATTR_FILE       (1 << 13)
#define ATTR_KILL_PRIV  (1 << 14)
#define ATTR_OPEN       (1 << 15) /* Truncating from open(O_TRUNC) */
#define ATTR_TIMES_SET  (1 << 16)
#define ATTR_TOUCH      (1 << 17)

/*
 * Whiteout is represented by a char device.  The following constants define the
 * mode and device number to use.
 */
#define WHITEOUT_MODE 0
#define WHITEOUT_DEV 0

/*
 * This is the Inode Attributes structure, used for notify_change().  It
 * uses the above definitions as flags, to know which values have changed.
 * Also, in this manner, a Filesystem can look at only the values it cares
 * about.  Basically, these are the attributes that the VFS layer can
 * request to change from the FS layer.
 *
 * Derek Atkins <warlord@MIT.EDU> 94-10-20
 */
struct iattr {
        unsigned int    ia_valid;
        umode_t         ia_mode;
        kuid_t          ia_uid;
        kgid_t          ia_gid;
        loff_t          ia_size;
        struct timespec64 ia_atime;
        struct timespec64 ia_mtime;
        struct timespec64 ia_ctime;

        /*
         * Not an attribute, but an auxiliary info for filesystems wanting to
         * implement an ftruncate() like method.  NOTE: filesystem should
         * check for (ia_valid & ATTR_FILE), and not for (ia_file != NULL).
         */
        struct file     *ia_file;
};

/*
 * Includes for diskquotas.
 */
#include <linux/quota.h>

/*
 * Maximum number of layers of fs stack.  Needs to be limited to
 * prevent kernel stack overflow
 */
#define FILESYSTEM_MAX_STACK_DEPTH 2

/** 
 * enum positive_aop_returns - aop return codes with specific semantics
 *
 * @AOP_WRITEPAGE_ACTIVATE: Informs the caller that page writeback has
 *                          completed, that the page is still locked, and
 *                          should be considered active.  The VM uses this hint
 *                          to return the page to the active list -- it won't
 *                          be a candidate for writeback again in the near
 *                          future.  Other callers must be careful to unlock
 *                          the page if they get this return.  Returned by
 *                          writepage(); 
 *
 * @AOP_TRUNCATED_PAGE: The AOP method that was handed a locked page has
 *                      unlocked it and the page might have been truncated.
 *                      The caller should back up to acquiring a new page and
 *                      trying again.  The aop will be taking reasonable
 *                      precautions not to livelock.  If the caller held a page
 *                      reference, it should drop it before retrying.  Returned
 *                      by readpage().
 *
 * address_space_operation functions return these large constants to indicate
 * special semantics to the caller.  These are much larger than the bytes in a
 * page to allow for functions that return the number of bytes operated on in a
 * given page.
 */

enum positive_aop_returns {
        AOP_WRITEPAGE_ACTIVATE  = 0x80000,
        AOP_TRUNCATED_PAGE      = 0x80001,
};

#define AOP_FLAG_CONT_EXPAND            0x0001 /* called from cont_expand */
#define AOP_FLAG_NOFS                   0x0002 /* used by filesystem to direct
                                                * helper code (eg buffer layer)
                                                * to clear GFP_FS from alloc */

/*
 * oh the beauties of C type declarations.
 */
struct page;
struct address_space;
struct writeback_control;

/*
 * Write life time hint values.
 * Stored in struct inode as u8.
 */
enum rw_hint {
        WRITE_LIFE_NOT_SET      = 0,
        WRITE_LIFE_NONE         = RWH_WRITE_LIFE_NONE,
        WRITE_LIFE_SHORT        = RWH_WRITE_LIFE_SHORT,
        WRITE_LIFE_MEDIUM       = RWH_WRITE_LIFE_MEDIUM,
        WRITE_LIFE_LONG         = RWH_WRITE_LIFE_LONG,
        WRITE_LIFE_EXTREME      = RWH_WRITE_LIFE_EXTREME,
};

#define IOCB_EVENTFD            (1 << 0)
#define IOCB_APPEND             (1 << 1)
#define IOCB_DIRECT             (1 << 2)
#define IOCB_HIPRI              (1 << 3)
#define IOCB_DSYNC              (1 << 4)
#define IOCB_SYNC               (1 << 5)
#define IOCB_WRITE              (1 << 6)
#define IOCB_NOWAIT             (1 << 7)

struct kiocb {
        struct file             *ki_filp;

        /* The 'ki_filp' pointer is shared in a union for aio */
        randomized_struct_fields_start

        loff_t                  ki_pos;
        void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
        void                    *private;
        int                     ki_flags;
        u16                     ki_hint;
        u16                     ki_ioprio; /* See linux/ioprio.h */

        randomized_struct_fields_end
};

static inline bool is_sync_kiocb(struct kiocb *kiocb)
{
        return kiocb->ki_complete == NULL;
}

/*
 * "descriptor" for what we're up to with a read.
 * This allows us to use the same read code yet
 * have multiple different users of the data that
 * we read from a file.
 *
 * The simplest case just copies the data to user
 * mode.
 */
typedef struct {
        size_t written;
        size_t count;
        union {
                char __user *buf;
                void *data;
        } arg;
        int error;
} read_descriptor_t;

typedef int (*read_actor_t)(read_descriptor_t *, struct page *,
                unsigned long, unsigned long);

struct address_space_operations {
        int (*writepage)(struct page *page, struct writeback_control *wbc);
        int (*readpage)(struct file *, struct page *);

        /* Write back some dirty pages from this mapping. */
        int (*writepages)(struct address_space *, struct writeback_control *);

        /* Set a page dirty.  Return true if this dirtied it */
        int (*set_page_dirty)(struct page *page);

        /*
         * Reads in the requested pages. Unlike ->readpage(), this is
         * PURELY used for read-ahead!.
         */
        int (*readpages)(struct file *filp, struct address_space *mapping,
                        struct list_head *pages, unsigned nr_pages);

        int (*write_begin)(struct file *, struct address_space *mapping,
                                loff_t pos, unsigned len, unsigned flags,
                                struct page **pagep, void **fsdata);
        int (*write_end)(struct file *, struct address_space *mapping,
                                loff_t pos, unsigned len, unsigned copied,
                                struct page *page, void *fsdata);

        /* Unfortunately this kludge is needed for FIBMAP. Don't use it */
        sector_t (*bmap)(struct address_space *, sector_t);
        void (*invalidatepage) (struct page *, unsigned int, unsigned int);
        int (*releasepage) (struct page *, gfp_t);
        void (*freepage)(struct page *);
        ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
        /*
         * migrate the contents of a page to the specified target. If
         * migrate_mode is MIGRATE_ASYNC, it must not block.
         */
        int (*migratepage) (struct address_space *,
                        struct page *, struct page *, enum migrate_mode);
        bool (*isolate_page)(struct page *, isolate_mode_t);
        void (*putback_page)(struct page *);
        int (*launder_page) (struct page *);
        int (*is_partially_uptodate) (struct page *, unsigned long,
                                        unsigned long);
        void (*is_dirty_writeback) (struct page *, bool *, bool *);
        int (*error_remove_page)(struct address_space *, struct page *);

        /* swapfile support */
        int (*swap_activate)(struct swap_info_struct *sis, struct file *file,
                                sector_t *span);
        void (*swap_deactivate)(struct file *file);
};

extern const struct address_space_operations empty_aops;

/*
 * pagecache_write_begin/pagecache_write_end must be used by general code
 * to write into the pagecache.
 */
int pagecache_write_begin(struct file *, struct address_space *mapping,
                                loff_t pos, unsigned len, unsigned flags,
                                struct page **pagep, void **fsdata);

int pagecache_write_end(struct file *, struct address_space *mapping,
                                loff_t pos, unsigned len, unsigned copied,
                                struct page *page, void *fsdata);

struct address_space {
        struct inode            *host;          /* owner: inode, block_device */
        struct radix_tree_root  i_pages;        /* cached pages */
        atomic_t                i_mmap_writable;/* count VM_SHARED mappings */
        struct rb_root_cached   i_mmap;         /* tree of private and shared mappings */
        struct rw_semaphore     i_mmap_rwsem;   /* protect tree, count, list */
        /* Protected by the i_pages lock */
        unsigned long           nrpages;        /* number of total pages */
        /* number of shadow or DAX exceptional entries */
        unsigned long           nrexceptional;
        pgoff_t                 writeback_index;/* writeback starts here */
        const struct address_space_operations *a_ops;   /* methods */
        unsigned long           flags;          /* error bits */
        spinlock_t              private_lock;   /* for use by the address_space */
        gfp_t                   gfp_mask;       /* implicit gfp mask for allocations */
        struct list_head        private_list;   /* for use by the address_space */
        void                    *private_data;  /* ditto */
        errseq_t                wb_err;
} __attribute__((aligned(sizeof(long)))) __randomize_layout;
        /*
         * On most architectures that alignment is already the case; but
         * must be enforced here for CRIS, to let the least significant bit
         * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
         */
struct request_queue;

struct block_device {
        dev_t                   bd_dev;  /* not a kdev_t - it's a search key */
        int                     bd_openers;
        struct inode *          bd_inode;       /* will die */
        struct super_block *    bd_super;
        struct mutex            bd_mutex;       /* open/close mutex */
        void *                  bd_claiming;
        void *                  bd_holder;
        int                     bd_holders;
        bool                    bd_write_holder;
#ifdef CONFIG_SYSFS
        struct list_head        bd_holder_disks;
#endif
        struct block_device *   bd_contains;
        unsigned                bd_block_size;
        u8                      bd_partno;
        struct hd_struct *      bd_part;
        /* number of times partitions within this device have been opened. */
        unsigned                bd_part_count;
        int                     bd_invalidated;
        struct gendisk *        bd_disk;
        struct request_queue *  bd_queue;
        struct backing_dev_info *bd_bdi;
        struct list_head        bd_list;
        /*
         * Private data.  You must have bd_claim'ed the block_device
         * to use this.  NOTE:  bd_claim allows an owner to claim
         * the same device multiple times, the owner must take special
         * care to not mess up bd_private for that case.
         */
        unsigned long           bd_private;

        /* The counter of freeze processes */
        int                     bd_fsfreeze_count;
        /* Mutex for freeze */
        struct mutex            bd_fsfreeze_mutex;
} __randomize_layout;

/*
 * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
 * radix trees
 */
#define PAGECACHE_TAG_DIRTY     0
#define PAGECACHE_TAG_WRITEBACK 1
#define PAGECACHE_TAG_TOWRITE   2

int mapping_tagged(struct address_space *mapping, int tag);

static inline void i_mmap_lock_write(struct address_space *mapping)
{
        down_write(&mapping->i_mmap_rwsem);
}

static inline void i_mmap_unlock_write(struct address_space *mapping)
{
        up_write(&mapping->i_mmap_rwsem);
}

static inline void i_mmap_lock_read(struct address_space *mapping)
{
        down_read(&mapping->i_mmap_rwsem);
}

static inline void i_mmap_unlock_read(struct address_space *mapping)
{
        up_read(&mapping->i_mmap_rwsem);
}

/*
 * Might pages of this file be mapped into userspace?
 */
static inline int mapping_mapped(struct address_space *mapping)
{
        return  !RB_EMPTY_ROOT(&mapping->i_mmap.rb_root);
}

/*
 * Might pages of this file have been modified in userspace?
 * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap_pgoff
 * marks vma as VM_SHARED if it is shared, and the file was opened for
 * writing i.e. vma may be mprotected writable even if now readonly.
 *
 * If i_mmap_writable is negative, no new writable mappings are allowed. You
 * can only deny writable mappings, if none exists right now.
 */
static inline int mapping_writably_mapped(struct address_space *mapping)
{
        return atomic_read(&mapping->i_mmap_writable) > 0;
}

static inline int mapping_map_writable(struct address_space *mapping)
{
        return atomic_inc_unless_negative(&mapping->i_mmap_writable) ?
                0 : -EPERM;
}

static inline void mapping_unmap_writable(struct address_space *mapping)
{
        atomic_dec(&mapping->i_mmap_writable);
}

static inline int mapping_deny_writable(struct address_space *mapping)
{
        return atomic_dec_unless_positive(&mapping->i_mmap_writable) ?
                0 : -EBUSY;
}

static inline void mapping_allow_writable(struct address_space *mapping)
{
        atomic_inc(&mapping->i_mmap_writable);
}

/*
 * Use sequence counter to get consistent i_size on 32-bit processors.
 */
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
#include <linux/seqlock.h>
#define __NEED_I_SIZE_ORDERED
#define i_size_ordered_init(inode) seqcount_init(&inode->i_size_seqcount)
#else
#define i_size_ordered_init(inode) do { } while (0)
#endif

struct posix_acl;
#define ACL_NOT_CACHED ((void *)(-1))
#define ACL_DONT_CACHE ((void *)(-3))

static inline struct posix_acl *
uncached_acl_sentinel(struct task_struct *task)
{
        return (void *)task + 1;
}

static inline bool
is_uncached_acl(struct posix_acl *acl)
{
        return (long)acl & 1;
}

#define IOP_FASTPERM    0x0001
#define IOP_LOOKUP      0x0002
#define IOP_NOFOLLOW    0x0004
#define IOP_XATTR       0x0008
#define IOP_DEFAULT_READLINK    0x0010

struct fsnotify_mark_connector;

/*
 * Keep mostly read-only and often accessed (especially for
 * the RCU path lookup and 'stat' data) fields at the beginning
 * of the 'struct inode'
 */
struct inode {
        umode_t                 i_mode;
        unsigned short          i_opflags;
        kuid_t                  i_uid;
        kgid_t                  i_gid;
        unsigned int            i_flags;

#ifdef CONFIG_FS_POSIX_ACL
        struct posix_acl        *i_acl;
        struct posix_acl        *i_default_acl;
#endif

        const struct inode_operations   *i_op;
        struct super_block      *i_sb;
        struct address_space    *i_mapping;

#ifdef CONFIG_SECURITY
        void                    *i_security;
#endif

        /* Stat data, not accessed from path walking */
        unsigned long           i_ino;
        /*
         * Filesystems may only read i_nlink directly.  They shall use the
         * following functions for modification:
         *
         *    (set|clear|inc|drop)_nlink
         *    inode_(inc|dec)_link_count
         */
        union {
                const unsigned int i_nlink;
                unsigned int __i_nlink;
        };
        dev_t                   i_rdev;
        loff_t                  i_size;
        struct timespec64       i_atime;
        struct timespec64       i_mtime;
        struct timespec64       i_ctime;
        spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_size */
        unsigned short          i_bytes;
        u8                      i_blkbits;
        u8                      i_write_hint;
        blkcnt_t                i_blocks;

#ifdef __NEED_I_SIZE_ORDERED
        seqcount_t              i_size_seqcount;
#endif

        /* Misc */
        unsigned long           i_state;
        struct rw_semaphore     i_rwsem;

        unsigned long           dirtied_when;   /* jiffies of first dirtying */
        unsigned long           dirtied_time_when;

        struct hlist_node       i_hash;
        struct list_head        i_io_list;      /* backing dev IO list */
#ifdef CONFIG_CGROUP_WRITEBACK
        struct bdi_writeback    *i_wb;          /* the associated cgroup wb */

        /* foreign inode detection, see wbc_detach_inode() */
        int                     i_wb_frn_winner;
        u16                     i_wb_frn_avg_time;
        u16                     i_wb_frn_history;
#endif
        struct list_head        i_lru;          /* inode LRU list */
        struct list_head        i_sb_list;
        struct list_head        i_wb_list;      /* backing dev writeback list */
        union {
                struct hlist_head       i_dentry;
                struct rcu_head         i_rcu;
        };
        atomic64_t              i_version;
        atomic64_t              i_sequence; /* see futex */
        atomic_t                i_count;
        atomic_t                i_dio_count;
        atomic_t                i_writecount;
#ifdef CONFIG_IMA
        atomic_t                i_readcount; /* struct files open RO */
#endif
        const struct file_operations    *i_fop; /* former ->i_op->default_file_ops */
        struct file_lock_context        *i_flctx;
        struct address_space    i_data;
        struct list_head        i_devices;
        union {
                struct pipe_inode_info  *i_pipe;
                struct block_device     *i_bdev;
                struct cdev             *i_cdev;
                char                    *i_link;
                unsigned                i_dir_seq;
        };

        __u32                   i_generation;

#ifdef CONFIG_FSNOTIFY
        __u32                   i_fsnotify_mask; /* all events this inode cares about */
        struct fsnotify_mark_connector __rcu    *i_fsnotify_marks;
#endif

#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
        struct fscrypt_info     *i_crypt_info;
#endif

        void                    *i_private; /* fs or device private pointer */
} __randomize_layout;

static inline unsigned int i_blocksize(const struct inode *node)
{
        return (1 << node->i_blkbits);
}

static inline int inode_unhashed(struct inode *inode)
{
        return hlist_unhashed(&inode->i_hash);
}

/*
 * __mark_inode_dirty expects inodes to be hashed.  Since we don't
 * want special inodes in the fileset inode space, we make them
 * appear hashed, but do not put on any lists.  hlist_del()
 * will work fine and require no locking.
 */
static inline void inode_fake_hash(struct inode *inode)
{
        hlist_add_fake(&inode->i_hash);
}

/*
 * inode->i_mutex nesting subclasses for the lock validator:
 *
 * 0: the object of the current VFS operation
 * 1: parent
 * 2: child/target
 * 3: xattr
 * 4: second non-directory
 * 5: second parent (when locking independent directories in rename)
 *
 * I_MUTEX_NONDIR2 is for certain operations (such as rename) which lock two
 * non-directories at once.
 *
 * The locking order between these classes is
 * parent[2] -> child -> grandchild -> normal -> xattr -> second non-directory
 */
enum inode_i_mutex_lock_class
{
        I_MUTEX_NORMAL,
        I_MUTEX_PARENT,
        I_MUTEX_CHILD,
        I_MUTEX_XATTR,
        I_MUTEX_NONDIR2,
        I_MUTEX_PARENT2,
};

static inline void inode_lock(struct inode *inode)
{
        down_write(&inode->i_rwsem);
}

static inline void inode_unlock(struct inode *inode)
{
        up_write(&inode->i_rwsem);
}

static inline void inode_lock_shared(struct inode *inode)
{
        down_read(&inode->i_rwsem);
}

static inline void inode_unlock_shared(struct inode *inode)
{
        up_read(&inode->i_rwsem);
}

static inline int inode_trylock(struct inode *inode)
{
        return down_write_trylock(&inode->i_rwsem);
}

static inline int inode_trylock_shared(struct inode *inode)
{
        return down_read_trylock(&inode->i_rwsem);
}

static inline int inode_is_locked(struct inode *inode)
{
        return rwsem_is_locked(&inode->i_rwsem);
}

static inline void inode_lock_nested(struct inode *inode, unsigned subclass)
{
        down_write_nested(&inode->i_rwsem, subclass);
}

static inline void inode_lock_shared_nested(struct inode *inode, unsigned subclass)
{
        down_read_nested(&inode->i_rwsem, subclass);
}

void lock_two_nondirectories(struct inode *, struct inode*);
void unlock_two_nondirectories(struct inode *, struct inode*);

/*
 * NOTE: in a 32bit arch with a preemptable kernel and
 * an UP compile the i_size_read/write must be atomic
 * with respect to the local cpu (unlike with preempt disabled),
 * but they don't need to be atomic with respect to other cpus like in
 * true SMP (so they need either to either locally disable irq around
 * the read or for example on x86 they can be still implemented as a
 * cmpxchg8b without the need of the lock prefix). For SMP compiles
 * and 64bit archs it makes no difference if preempt is enabled or not.
 */
static inline loff_t i_size_read(const struct inode *inode)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
        loff_t i_size;
        unsigned int seq;

        do {
                seq = read_seqcount_begin(&inode->i_size_seqcount);
                i_size = inode->i_size;
        } while (read_seqcount_retry(&inode->i_size_seqcount, seq));
        return i_size;
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
        loff_t i_size;

        preempt_disable();
        i_size = inode->i_size;
        preempt_enable();
        return i_size;
#else
        return inode->i_size;
#endif
}

/*
 * NOTE: unlike i_size_read(), i_size_write() does need locking around it
 * (normally i_mutex), otherwise on 32bit/SMP an update of i_size_seqcount
 * can be lost, resulting in subsequent i_size_read() calls spinning forever.
 */
static inline void i_size_write(struct inode *inode, loff_t i_size)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
        preempt_disable();
        write_seqcount_begin(&inode->i_size_seqcount);
        inode->i_size = i_size;
        write_seqcount_end(&inode->i_size_seqcount);
        preempt_enable();
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
        preempt_disable();
        inode->i_size = i_size;
        preempt_enable();
#else
        inode->i_size = i_size;
#endif
}

static inline unsigned iminor(const struct inode *inode)
{
        return MINOR(inode->i_rdev);
}

static inline unsigned imajor(const struct inode *inode)
{
        return MAJOR(inode->i_rdev);
}

extern struct block_device *I_BDEV(struct inode *inode);

struct fown_struct {
        rwlock_t lock;          /* protects pid, uid, euid fields */
        struct pid *pid;        /* pid or -pgrp where SIGIO should be sent */
        enum pid_type pid_type; /* Kind of process group SIGIO should be sent to */
        kuid_t uid, euid;       /* uid/euid of process setting the owner */
        int signum;             /* posix.1b rt signal to be delivered on IO */
};

/*
 * Track a single file's readahead state
 */
struct file_ra_state {
        pgoff_t start;                  /* where readahead started */
        unsigned int size;              /* # of readahead pages */
        unsigned int async_size;        /* do asynchronous readahead when
                                           there are only # of pages ahead */

        unsigned int ra_pages;          /* Maximum readahead window */
        unsigned int mmap_miss;         /* Cache miss stat for mmap accesses */
        loff_t prev_pos;                /* Cache last read() position */
};

/*
 * Check if @index falls in the readahead windows.
 */
static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
{
        return (index >= ra->start &&
                index <  ra->start + ra->size);
}

struct file {
        union {
                struct llist_node       fu_llist;
                struct rcu_head         fu_rcuhead;
        } f_u;
        struct path             f_path;
        struct inode            *f_inode;       /* cached value */
        const struct file_operations    *f_op;

        /*
         * Protects f_ep_links, f_flags.
         * Must not be taken from IRQ context.
         */
        spinlock_t              f_lock;
        enum rw_hint            f_write_hint;
        atomic_long_t           f_count;
        unsigned int            f_flags;
        fmode_t                 f_mode;
        struct mutex            f_pos_lock;
        loff_t                  f_pos;
        struct fown_struct      f_owner;
        const struct cred       *f_cred;
        struct file_ra_state    f_ra;

        u64                     f_version;
#ifdef CONFIG_SECURITY
        void                    *f_security;
#endif
        /* needed for tty driver, and maybe others */
        void                    *private_data;

#ifdef CONFIG_EPOLL
        /* Used by fs/eventpoll.c to link all the hooks to this file */
        struct list_head        f_ep_links;
        struct list_head        f_tfile_llink;
#endif /* #ifdef CONFIG_EPOLL */
        struct address_space    *f_mapping;
        errseq_t                f_wb_err;
} __randomize_layout
  __attribute__((aligned(4)));  /* lest something weird decides that 2 is OK */

struct file_handle {
        __u32 handle_bytes;
        int handle_type;
        /* file identifier */
        unsigned char f_handle[];
};

static inline struct file *get_file(struct file *f)
{
        atomic_long_inc(&f->f_count);
        return f;
}
#define get_file_rcu(x) atomic_long_inc_not_zero(&(x)->f_count)
#define fput_atomic(x)  atomic_long_add_unless(&(x)->f_count, -1, 1)
#define file_count(x)   atomic_long_read(&(x)->f_count)

#define MAX_NON_LFS     ((1UL<<31) - 1)

/* Page cache limit. The filesystems should put that into their s_maxbytes 
   limits, otherwise bad things can happen in VM. */ 
#if BITS_PER_LONG==32
#define MAX_LFS_FILESIZE        ((loff_t)ULONG_MAX << PAGE_SHIFT)
#elif BITS_PER_LONG==64
#define MAX_LFS_FILESIZE        ((loff_t)LLONG_MAX)
#endif

#define FL_POSIX        1
#define FL_FLOCK        2
#define FL_DELEG        4       /* NFSv4 delegation */
#define FL_ACCESS       8       /* not trying to lock, just looking */
#define FL_EXISTS       16      /* when unlocking, test for existence */
#define FL_LEASE        32      /* lease held on this file */
#define FL_CLOSE        64      /* unlock on close */
#define FL_SLEEP        128     /* A blocking lock */
#define FL_DOWNGRADE_PENDING    256 /* Lease is being downgraded */
#define FL_UNLOCK_PENDING       512 /* Lease is being broken */
#define FL_OFDLCK       1024    /* lock is "owned" by struct file */
#define FL_LAYOUT       2048    /* outstanding pNFS layout */

#define FL_CLOSE_POSIX (FL_POSIX | FL_CLOSE)

/*
 * Special return value from posix_lock_file() and vfs_lock_file() for
 * asynchronous locking.
 */
#define FILE_LOCK_DEFERRED 1

/* legacy typedef, should eventually be removed */
typedef void *fl_owner_t;

struct file_lock;

struct file_lock_operations {
        void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
        void (*fl_release_private)(struct file_lock *);
};

struct lock_manager_operations {
        int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
        unsigned long (*lm_owner_key)(struct file_lock *);
        fl_owner_t (*lm_get_owner)(fl_owner_t);
        void (*lm_put_owner)(fl_owner_t);
        void (*lm_notify)(struct file_lock *);  /* unblock callback */
        int (*lm_grant)(struct file_lock *, int);
        bool (*lm_break)(struct file_lock *);
        int (*lm_change)(struct file_lock *, int, struct list_head *);
        void (*lm_setup)(struct file_lock *, void **);
};

struct lock_manager {
        struct list_head list;
        /*
         * NFSv4 and up also want opens blocked during the grace period;
         * NLM doesn't care:
         */
        bool block_opens;
};

struct net;
void locks_start_grace(struct net *, struct lock_manager *);
void locks_end_grace(struct lock_manager *);
bool locks_in_grace(struct net *);
bool opens_in_grace(struct net *);

/* that will die - we need it for nfs_lock_info */
#include <linux/nfs_fs_i.h>

/*
 * struct file_lock represents a generic "file lock". It's used to represent
 * POSIX byte range locks, BSD (flock) locks, and leases. It's important to
 * note that the same struct is used to represent both a request for a lock and
 * the lock itself, but the same object is never used for both.
 *
 * FIXME: should we create a separate "struct lock_request" to help distinguish
 * these two uses?
 *
 * The varous i_flctx lists are ordered by:
 *
 * 1) lock owner
 * 2) lock range start
 * 3) lock range end
 *
 * Obviously, the last two criteria only matter for POSIX locks.
 */
struct file_lock {
        struct file_lock *fl_next;      /* singly linked list for this inode  */
        struct list_head fl_list;       /* link into file_lock_context */
        struct hlist_node fl_link;      /* node in global lists */
        struct list_head fl_block;      /* circular list of blocked processes */
        fl_owner_t fl_owner;
        unsigned int fl_flags;
        unsigned char fl_type;
        unsigned int fl_pid;
        int fl_link_cpu;                /* what cpu's list is this on? */
        wait_queue_head_t fl_wait;
        struct file *fl_file;
        loff_t fl_start;
        loff_t fl_end;

        struct fasync_struct *  fl_fasync; /* for lease break notifications */
        /* for lease breaks: */
        unsigned long fl_break_time;
        unsigned long fl_downgrade_time;

        const struct file_lock_operations *fl_ops;      /* Callbacks for filesystems */
        const struct lock_manager_operations *fl_lmops; /* Callbacks for lockmanagers */
        union {
                struct nfs_lock_info    nfs_fl;
                struct nfs4_lock_info   nfs4_fl;
                struct {
                        struct list_head link;  /* link in AFS vnode's pending_locks list */
                        int state;              /* state of grant or error if -ve */
                } afs;
        } fl_u;
} __randomize_layout;

struct file_lock_context {
        spinlock_t              flc_lock;
        struct list_head        flc_flock;
        struct list_head        flc_posix;
        struct list_head        flc_lease;
};

/* The following constant reflects the upper bound of the file/locking space */
#ifndef OFFSET_MAX
#define INT_LIMIT(x)    (~((x)1 << (sizeof(x)*8 - 1)))
#define OFFSET_MAX      INT_LIMIT(loff_t)
#define OFFT_OFFSET_MAX INT_LIMIT(off_t)
#endif

extern void send_sigio(struct fown_struct *fown, int fd, int band);

#define locks_inode(f) file_inode(f)

#ifdef CONFIG_FILE_LOCKING
extern int fcntl_getlk(struct file *, unsigned int, struct flock *);
extern int fcntl_setlk(unsigned int, struct file *, unsigned int,
                        struct flock *);

#if BITS_PER_LONG == 32
extern int fcntl_getlk64(struct file *, unsigned int, struct flock64 *);
extern int fcntl_setlk64(unsigned int, struct file *, unsigned int,
                        struct flock64 *);
#endif

extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg);
extern int fcntl_getlease(struct file *filp);

/* fs/locks.c */
void locks_free_lock_context(struct inode *inode);
void locks_free_lock(struct file_lock *fl);
extern void locks_init_lock(struct file_lock *);
extern struct file_lock * locks_alloc_lock(void);
extern void locks_copy_lock(struct file_lock *, struct file_lock *);
extern void locks_copy_conflock(struct file_lock *, struct file_lock *);
extern void locks_remove_posix(struct file *, fl_owner_t);
extern void locks_remove_file(struct file *);
extern void locks_release_private(struct file_lock *);
extern void posix_test_lock(struct file *, struct file_lock *);
extern int posix_lock_file(struct file *, struct file_lock *, struct file_lock *);
extern int posix_unblock_lock(struct file_lock *);
extern int vfs_test_lock(struct file *, struct file_lock *);
extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
extern int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl);
extern int __break_lease(struct inode *inode, unsigned int flags, unsigned int type);
extern void lease_get_mtime(struct inode *, struct timespec64 *time);
extern int generic_setlease(struct file *, long, struct file_lock **, void **priv);
extern int vfs_setlease(struct file *, long, struct file_lock **, void **);
extern int lease_modify(struct file_lock *, int, struct list_head *);
struct files_struct;
extern void show_fd_locks(struct seq_file *f,
                         struct file *filp, struct files_struct *files);
#else /* !CONFIG_FILE_LOCKING */
static inline int fcntl_getlk(struct file *file, unsigned int cmd,
                              struct flock __user *user)
{
        return -EINVAL;
}

static inline int fcntl_setlk(unsigned int fd, struct file *file,
                              unsigned int cmd, struct flock __user *user)
{
        return -EACCES;
}

#if BITS_PER_LONG == 32
static inline int fcntl_getlk64(struct file *file, unsigned int cmd,
                                struct flock64 __user *user)
{
        return -EINVAL;
}

static inline int fcntl_setlk64(unsigned int fd, struct file *file,
                                unsigned int cmd, struct flock64 __user *user)
{
        return -EACCES;
}
#endif
static inline int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
{
        return -EINVAL;
}

static inline int fcntl_getlease(struct file *filp)
{
        return F_UNLCK;
}

static inline void
locks_free_lock_context(struct inode *inode)
{
}

static inline void locks_init_lock(struct file_lock *fl)
{
        return;
}

static inline void locks_copy_conflock(struct file_lock *new, struct file_lock *fl)
{
        return;
}

static inline void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
{
        return;
}

static inline void locks_remove_posix(struct file *filp, fl_owner_t owner)
{
        return;
}

static inline void locks_remove_file(struct file *filp)
{
        return;
}

static inline void posix_test_lock(struct file *filp, struct file_lock *fl)
{
        return;
}

static inline int posix_lock_file(struct file *filp, struct file_lock *fl,
                                  struct file_lock *conflock)
{
        return -ENOLCK;
}

static inline int posix_unblock_lock(struct file_lock *waiter)
{
        return -ENOENT;
}

static inline int vfs_test_lock(struct file *filp, struct file_lock *fl)
{
        return 0;
}

static inline int vfs_lock_file(struct file *filp, unsigned int cmd,
                                struct file_lock *fl, struct file_lock *conf)
{
        return -ENOLCK;
}

static inline int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
{
        return 0;
}

static inline int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl)
{
        return -ENOLCK;
}

static inline int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
{
        return 0;
}

static inline void lease_get_mtime(struct inode *inode,
                                   struct timespec64 *time)
{
        return;
}

static inline int generic_setlease(struct file *filp, long arg,
                                    struct file_lock **flp, void **priv)
{
        return -EINVAL;
}

static inline int vfs_setlease(struct file *filp, long arg,
                               struct file_lock **lease, void **priv)
{
        return -EINVAL;
}

static inline int lease_modify(struct file_lock *fl, int arg,
                               struct list_head *dispose)
{
        return -EINVAL;
}

struct files_struct;
static inline void show_fd_locks(struct seq_file *f,
                        struct file *filp, struct files_struct *files) {}
#endif /* !CONFIG_FILE_LOCKING */

static inline struct inode *file_inode(const struct file *f)
{
        return f->f_inode;
}

static inline struct dentry *file_dentry(const struct file *file)
{
        return d_real(file->f_path.dentry, file_inode(file));
}

static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
{
        return locks_lock_inode_wait(locks_inode(filp), fl);
}

struct fasync_struct {
        rwlock_t                fa_lock;
        int                     magic;
        int                     fa_fd;
        struct fasync_struct    *fa_next; /* singly linked list */
        struct file             *fa_file;
        struct rcu_head         fa_rcu;
};

#define FASYNC_MAGIC 0x4601

/* SMP safe fasync helpers: */
extern int fasync_helper(int, struct file *, int, struct fasync_struct **);
extern struct fasync_struct *fasync_insert_entry(int, struct file *, struct fasync_struct **, struct fasync_struct *);
extern int fasync_remove_entry(struct file *, struct fasync_struct **);
extern struct fasync_struct *fasync_alloc(void);
extern void fasync_free(struct fasync_struct *);

/* can be called from interrupts */
extern void kill_fasync(struct fasync_struct **, int, int);

extern void __f_setown(struct file *filp, struct pid *, enum pid_type, int force);
extern int f_setown(struct file *filp, unsigned long arg, int force);
extern void f_delown(struct file *filp);
extern pid_t f_getown(struct file *filp);
extern int send_sigurg(struct fown_struct *fown);

/*
 * sb->s_flags.  Note that these mirror the equivalent MS_* flags where
 * represented in both.
 */
#define SB_RDONLY        1      /* Mount read-only */
#define SB_NOSUID        2      /* Ignore suid and sgid bits */
#define SB_NODEV         4      /* Disallow access to device special files */
#define SB_NOEXEC        8      /* Disallow program execution */
#define SB_SYNCHRONOUS  16      /* Writes are synced at once */
#define SB_MANDLOCK     64      /* Allow mandatory locks on an FS */
#define SB_DIRSYNC      128     /* Directory modifications are synchronous */
#define SB_NOATIME      1024    /* Do not update access times. */
#define SB_NODIRATIME   2048    /* Do not update directory access times */
#define SB_SILENT       32768
#define SB_POSIXACL     (1<<16) /* VFS does not apply the umask */
#define SB_KERNMOUNT    (1<<22) /* this is a kern_mount call */
#define SB_I_VERSION    (1<<23) /* Update inode I_version field */
#define SB_LAZYTIME     (1<<25) /* Update the on-disk [acm]times lazily */

/* These sb flags are internal to the kernel */
#define SB_SUBMOUNT     (1<<26)
#define SB_NOSEC        (1<<28)
#define SB_BORN         (1<<29)
#define SB_ACTIVE       (1<<30)
#define SB_NOUSER       (1<<31)

/*
 *      Umount options
 */

#define MNT_FORCE       0x00000001      /* Attempt to forcibily umount */
#define MNT_DETACH      0x00000002      /* Just detach from the tree */
#define MNT_EXPIRE      0x00000004      /* Mark for expiry */
#define UMOUNT_NOFOLLOW 0x00000008      /* Don't follow symlink on umount */
#define UMOUNT_UNUSED   0x80000000      /* Flag guaranteed to be unused */

/* sb->s_iflags */
#define SB_I_CGROUPWB   0x00000001      /* cgroup-aware writeback enabled */
#define SB_I_NOEXEC     0x00000002      /* Ignore executables on this fs */
#define SB_I_NODEV      0x00000004      /* Ignore devices on this fs */
#define SB_I_MULTIROOT  0x00000008      /* Multiple roots to the dentry tree */

/* sb->s_iflags to limit user namespace mounts */
#define SB_I_USERNS_VISIBLE             0x00000010 /* fstype already mounted */
#define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020
#define SB_I_UNTRUSTED_MOUNTER          0x00000040

/* Possible states of 'frozen' field */
enum {
        SB_UNFROZEN = 0,                /* FS is unfrozen */
        SB_FREEZE_WRITE = 1,            /* Writes, dir ops, ioctls frozen */
        SB_FREEZE_PAGEFAULT = 2,        /* Page faults stopped as well */
        SB_FREEZE_FS = 3,               /* For internal FS use (e.g. to stop
                                         * internal threads if needed) */
        SB_FREEZE_COMPLETE = 4,         /* ->freeze_fs finished successfully */
};

#define SB_FREEZE_LEVELS (SB_FREEZE_COMPLETE - 1)

struct sb_writers {
        int                             frozen;         /* Is sb frozen? */
        wait_queue_head_t               wait_unfrozen;  /* for get_super_thawed() */
        struct percpu_rw_semaphore      rw_sem[SB_FREEZE_LEVELS];
};

struct super_block {
        struct list_head        s_list;         /* Keep this first */
        dev_t                   s_dev;          /* search index; _not_ kdev_t */
        unsigned char           s_blocksize_bits;
        unsigned long           s_blocksize;
        loff_t                  s_maxbytes;     /* Max file size */
        struct file_system_type *s_type;
        const struct super_operations   *s_op;
        const struct dquot_operations   *dq_op;
        const struct quotactl_ops       *s_qcop;
        const struct export_operations *s_export_op;
        unsigned long           s_flags;
        unsigned long           s_iflags;       /* internal SB_I_* flags */
        unsigned long           s_magic;
        struct dentry           *s_root;
        struct rw_semaphore     s_umount;
        int                     s_count;
        atomic_t                s_active;
#ifdef CONFIG_SECURITY
        void                    *s_security;
#endif
        const struct xattr_handler **s_xattr;
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
        const struct fscrypt_operations *s_cop;
#endif
        struct hlist_bl_head    s_roots;        /* alternate root dentries for NFS */
        struct list_head        s_mounts;       /* list of mounts; _not_ for fs use */
        struct block_device     *s_bdev;
        struct backing_dev_info *s_bdi;
        struct mtd_info         *s_mtd;
        struct hlist_node       s_instances;
        unsigned int            s_quota_types;  /* Bitmask of supported quota types */
        struct quota_info       s_dquot;        /* Diskquota specific options */

        struct sb_writers       s_writers;

        char                    s_id[32];       /* Informational name */
        uuid_t                  s_uuid;         /* UUID */

        void                    *s_fs_info;     /* Filesystem private info */
        unsigned int            s_max_links;
        fmode_t                 s_mode;

        /* Granularity of c/m/atime in ns.
           Cannot be worse than a second */
        u32                s_time_gran;

        /*
         * The next field is for VFS *only*. No filesystems have any business
         * even looking at it. You had been warned.
         */
        struct mutex s_vfs_rename_mutex;        /* Kludge */

        /*
         * Filesystem subtype.  If non-empty the filesystem type field
         * in /proc/mounts will be "type.subtype"
         */
        char *s_subtype;

        const struct dentry_operations *s_d_op; /* default d_op for dentries */

        /*
         * Saved pool identifier for cleancache (-1 means none)
         */
        int cleancache_poolid;

        struct shrinker s_shrink;       /* per-sb shrinker handle */

        /* Number of inodes with nlink == 0 but still referenced */
        atomic_long_t s_remove_count;

        /* Pending fsnotify inode refs */
        atomic_long_t s_fsnotify_inode_refs;

        /* Being remounted read-only */
        int s_readonly_remount;

        /* AIO completions deferred from interrupt context */
        struct workqueue_struct *s_dio_done_wq;
        struct hlist_head s_pins;

        /*
         * Owning user namespace and default context in which to
         * interpret filesystem uids, gids, quotas, device nodes,
         * xattrs and security labels.
         */
        struct user_namespace *s_user_ns;

        /*
         * Keep the lru lists last in the structure so they always sit on their
         * own individual cachelines.
         */
        struct list_lru         s_dentry_lru ____cacheline_aligned_in_smp;
        struct list_lru         s_inode_lru ____cacheline_aligned_in_smp;
        struct rcu_head         rcu;
        struct work_struct      destroy_work;

        struct mutex            s_sync_lock;    /* sync serialisation lock */

        /*
         * Indicates how deep in a filesystem stack this SB is
         */
        int s_stack_depth;

        /* s_inode_list_lock protects s_inodes */
        spinlock_t              s_inode_list_lock ____cacheline_aligned_in_smp;
        struct list_head        s_inodes;       /* all inodes */

        spinlock_t              s_inode_wblist_lock;
        struct list_head        s_inodes_wb;    /* writeback inodes */
} __randomize_layout;

/* Helper functions so that in most cases filesystems will
 * not need to deal directly with kuid_t and kgid_t and can
 * instead deal with the raw numeric values that are stored
 * in the filesystem.
 */
static inline uid_t i_uid_read(const struct inode *inode)
{
        return from_kuid(inode->i_sb->s_user_ns, inode->i_uid);
}

static inline gid_t i_gid_read(const struct inode *inode)
{
        return from_kgid(inode->i_sb->s_user_ns, inode->i_gid);
}

static inline void i_uid_write(struct inode *inode, uid_t uid)
{
        inode->i_uid = make_kuid(inode->i_sb->s_user_ns, uid);
}

static inline void i_gid_write(struct inode *inode, gid_t gid)
{
        inode->i_gid = make_kgid(inode->i_sb->s_user_ns, gid);
}

extern struct timespec64 timespec64_trunc(struct timespec64 t, unsigned gran);
extern struct timespec64 current_time(struct inode *inode);

/*
 * Snapshotting support.
 */

void __sb_end_write(struct super_block *sb, int level);
int __sb_start_write(struct super_block *sb, int level, bool wait);

#define __sb_writers_acquired(sb, lev)  \
        percpu_rwsem_acquire(&(sb)->s_writers.rw_sem[(lev)-1], 1, _THIS_IP_)
#define __sb_writers_release(sb, lev)   \
        percpu_rwsem_release(&(sb)->s_writers.rw_sem[(lev)-1], 1, _THIS_IP_)

/**
 * sb_end_write - drop write access to a superblock
 * @sb: the super we wrote to
 *
 * Decrement number of writers to the filesystem. Wake up possible waiters
 * wanting to freeze the filesystem.
 */
static inline void sb_end_write(struct super_block *sb)
{
        __sb_end_write(sb, SB_FREEZE_WRITE);
}

/**
 * sb_end_pagefault - drop write access to a superblock from a page fault
 * @sb: the super we wrote to
 *
 * Decrement number of processes handling write page fault to the filesystem.
 * Wake up possible waiters wanting to freeze the filesystem.
 */
static inline void sb_end_pagefault(struct super_block *sb)
{
        __sb_end_write(sb, SB_FREEZE_PAGEFAULT);
}

/**
 * sb_end_intwrite - drop write access to a superblock for internal fs purposes
 * @sb: the super we wrote to
 *
 * Decrement fs-internal number of writers to the filesystem.  Wake up possible
 * waiters wanting to freeze the filesystem.
 */
static inline void sb_end_intwrite(struct super_block *sb)
{
        __sb_end_write(sb, SB_FREEZE_FS);
}

/**
 * sb_start_write - get write access to a superblock
 * @sb: the super we write to
 *
 * When a process wants to write data or metadata to a file system (i.e. dirty
 * a page or an inode), it should embed the operation in a sb_start_write() -
 * sb_end_write() pair to get exclusion against file system freezing. This
 * function increments number of writers preventing freezing. If the file
 * system is already frozen, the function waits until the file system is
 * thawed.
 *
 * Since freeze protection behaves as a lock, users have to preserve
 * ordering of freeze protection and other filesystem locks. Generally,
 * freeze protection should be the outermost lock. In particular, we have:
 *
 * sb_start_write
 *   -> i_mutex                 (write path, truncate, directory ops, ...)
 *   -> s_umount                (freeze_super, thaw_super)
 */
static inline void sb_start_write(struct super_block *sb)
{
        __sb_start_write(sb, SB_FREEZE_WRITE, true);
}

static inline int sb_start_write_trylock(struct super_block *sb)
{
        return __sb_start_write(sb, SB_FREEZE_WRITE, false);
}

/**
 * sb_start_pagefault - get write access to a superblock from a page fault
 * @sb: the super we write to
 *
 * When a process starts handling write page fault, it should embed the
 * operation into sb_start_pagefault() - sb_end_pagefault() pair to get
 * exclusion against file system freezing. This is needed since the page fault
 * is going to dirty a page. This function increments number of running page
 * faults preventing freezing. If the file system is already frozen, the
 * function waits until the file system is thawed.
 *
 * Since page fault freeze protection behaves as a lock, users have to preserve
 * ordering of freeze protection and other filesystem locks. It is advised to
 * put sb_start_pagefault() close to mmap_sem in lock ordering. Page fault
 * handling code implies lock dependency:
 *
 * mmap_sem
 *   -> sb_start_pagefault
 */
static inline void sb_start_pagefault(struct super_block *sb)
{
        __sb_start_write(sb, SB_FREEZE_PAGEFAULT, true);
}

/*
 * sb_start_intwrite - get write access to a superblock for internal fs purposes
 * @sb: the super we write to
 *
 * This is the third level of protection against filesystem freezing. It is
 * free for use by a filesystem. The only requirement is that it must rank
 * below sb_start_pagefault.
 *
 * For example filesystem can call sb_start_intwrite() when starting a
 * transaction which somewhat eases handling of freezing for internal sources
 * of filesystem changes (internal fs threads, discarding preallocation on file
 * close, etc.).
 */
static inline void sb_start_intwrite(struct super_block *sb)
{
        __sb_start_write(sb, SB_FREEZE_FS, true);
}

static inline int sb_start_intwrite_trylock(struct super_block *sb)
{
        return __sb_start_write(sb, SB_FREEZE_FS, false);
}


extern bool inode_owner_or_capable(const struct inode *inode);

/*
 * VFS helper functions..
 */
extern int vfs_create(struct inode *, struct dentry *, umode_t, bool);
extern int vfs_mkdir(struct inode *, struct dentry *, umode_t);
extern int vfs_mknod(struct inode *, struct dentry *, umode_t, dev_t);
extern int vfs_symlink(struct inode *, struct dentry *, const char *);
extern int vfs_link(struct dentry *, struct inode *, struct dentry *, struct inode **);
extern int vfs_rmdir(struct inode *, struct dentry *);
extern int vfs_unlink(struct inode *, struct dentry *, struct inode **);
extern int vfs_rename(struct inode *, struct dentry *, struct inode *, struct dentry *, struct inode **, unsigned int);
extern int vfs_whiteout(struct inode *, struct dentry *);

extern struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode,
                                  int open_flag);

int vfs_mkobj(struct dentry *, umode_t,
                int (*f)(struct dentry *, umode_t, void *),
                void *);

extern long vfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

/*
 * VFS file helper functions.
 */
extern void inode_init_owner(struct inode *inode, const struct inode *dir,
                        umode_t mode);
extern bool may_open_dev(const struct path *path);
/*
 * VFS FS_IOC_FIEMAP helper definitions.
 */
struct fiemap_extent_info {
        unsigned int fi_flags;          /* Flags as passed from user */
        unsigned int fi_extents_mapped; /* Number of mapped extents */
        unsigned int fi_extents_max;    /* Size of fiemap_extent array */
        struct fiemap_extent __user *fi_extents_start; /* Start of
                                                        fiemap_extent array */
};
int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
                            u64 phys, u64 len, u32 flags);
int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);

/*
 * File types
 *
 * NOTE! These match bits 12..15 of stat.st_mode
 * (ie "(i_mode >> 12) & 15").
 */
#define DT_UNKNOWN      0
#define DT_FIFO         1
#define DT_CHR          2
#define DT_DIR          4
#define DT_BLK          6
#define DT_REG          8
#define DT_LNK          10
#define DT_SOCK         12
#define DT_WHT          14

/*
 * This is the "filldir" function type, used by readdir() to let
 * the kernel specify what kind of dirent layout it wants to have.
 * This allows the kernel to read directories into kernel space or
 * to have different dirent layouts depending on the binary type.
 */
struct dir_context;
typedef int (*filldir_t)(struct dir_context *, const char *, int, loff_t, u64,
                         unsigned);

struct dir_context {
        filldir_t actor;
        loff_t pos;
};

struct block_device_operations;

/* These macros are for out of kernel modules to test that
 * the kernel supports the unlocked_ioctl and compat_ioctl
 * fields in struct file_operations. */
#define HAVE_COMPAT_IOCTL 1
#define HAVE_UNLOCKED_IOCTL 1

/*
 * These flags let !MMU mmap() govern direct device mapping vs immediate
 * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
 *
 * NOMMU_MAP_COPY:      Copy can be mapped (MAP_PRIVATE)
 * NOMMU_MAP_DIRECT:    Can be mapped directly (MAP_SHARED)
 * NOMMU_MAP_READ:      Can be mapped for reading
 * NOMMU_MAP_WRITE:     Can be mapped for writing
 * NOMMU_MAP_EXEC:      Can be mapped for execution
 */
#define NOMMU_MAP_COPY          0x00000001
#define NOMMU_MAP_DIRECT        0x00000008
#define NOMMU_MAP_READ          VM_MAYREAD
#define NOMMU_MAP_WRITE         VM_MAYWRITE
#define NOMMU_MAP_EXEC          VM_MAYEXEC

#define NOMMU_VMFLAGS \
        (NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC)


struct iov_iter;

struct file_operations {
        struct module *owner;
        loff_t (*llseek) (struct file *, loff_t, int);
        ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
        ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
        ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
        ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
        int (*iterate) (struct file *, struct dir_context *);
        int (*iterate_shared) (struct file *, struct dir_context *);
        __poll_t (*poll) (struct file *, struct poll_table_struct *);
        long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
        long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
        int (*mmap) (struct file *, struct vm_area_struct *);
        unsigned long mmap_supported_flags;
        int (*open) (struct inode *, struct file *);
        int (*flush) (struct file *, fl_owner_t id);
        int (*release) (struct inode *, struct file *);
        int (*fsync) (struct file *, loff_t, loff_t, int datasync);
        int (*fasync) (int, struct file *, int);
        int (*lock) (struct file *, int, struct file_lock *);
        ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
        unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
        int (*check_flags)(int);
        int (*flock) (struct file *, int, struct file_lock *);
        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
        ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
        int (*setlease)(struct file *, long, struct file_lock **, void **);
        long (*fallocate)(struct file *file, int mode, loff_t offset,
                          loff_t len);
        void (*show_fdinfo)(struct seq_file *m, struct file *f);
#ifndef CONFIG_MMU
        unsigned (*mmap_capabilities)(struct file *);
#endif
        ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
                        loff_t, size_t, unsigned int);
        int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t,
                        u64);
        int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t,
                        u64);
        int (*fadvise)(struct file *, loff_t, loff_t, int);
} __randomize_layout;

struct inode_operations {
        struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
        const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
        int (*permission) (struct inode *, int);
        struct posix_acl * (*get_acl)(struct inode *, int);

        int (*readlink) (struct dentry *, char __user *,int);

        int (*create) (struct inode *,struct dentry *, umode_t, bool);
        int (*link) (struct dentry *,struct inode *,struct dentry *);
        int (*unlink) (struct inode *,struct dentry *);
        int (*symlink) (struct inode *,struct dentry *,const char *);
        int (*mkdir) (struct inode *,struct dentry *,umode_t);
        int (*rmdir) (struct inode *,struct dentry *);
        int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
        int (*rename) (struct inode *, struct dentry *,
                        struct inode *, struct dentry *, unsigned int);
        int (*setattr) (struct dentry *, struct iattr *);
        int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
        ssize_t (*listxattr) (struct dentry *, char *, size_t);
        int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
                      u64 len);
        int (*update_time)(struct inode *, struct timespec64 *, int);
        int (*atomic_open)(struct inode *, struct dentry *,
                           struct file *, unsigned open_flag,
                           umode_t create_mode);
        int (*tmpfile) (struct inode *, struct dentry *, umode_t);
        int (*set_acl)(struct inode *, struct posix_acl *, int);
} ____cacheline_aligned;

static inline ssize_t call_read_iter(struct file *file, struct kiocb *kio,
                                     struct iov_iter *iter)
{
        return file->f_op->read_iter(kio, iter);
}

static inline ssize_t call_write_iter(struct file *file, struct kiocb *kio,
                                      struct iov_iter *iter)
{
        return file->f_op->write_iter(kio, iter);
}

static inline int call_mmap(struct file *file, struct vm_area_struct *vma)
{
        return file->f_op->mmap(file, vma);
}

ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
                              unsigned long nr_segs, unsigned long fast_segs,
                              struct iovec *fast_pointer,
                              struct iovec **ret_pointer);

extern ssize_t __vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
                unsigned long, loff_t *, rwf_t);
extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
                                   loff_t, size_t, unsigned int);
extern int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
                                      struct inode *inode_out, loff_t pos_out,
                                      u64 *len, bool is_dedupe);
extern int do_clone_file_range(struct file *file_in, loff_t pos_in,
                               struct file *file_out, loff_t pos_out, u64 len);
extern int vfs_clone_file_range(struct file *file_in, loff_t pos_in,
                                struct file *file_out, loff_t pos_out, u64 len);
extern int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
                                         struct inode *dest, loff_t destoff,
                                         loff_t len, bool *is_same);
extern int vfs_dedupe_file_range(struct file *file,
                                 struct file_dedupe_range *same);
extern int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
                                     struct file *dst_file, loff_t dst_pos,
                                     u64 len);


struct super_operations {
        struct inode *(*alloc_inode)(struct super_block *sb);
        void (*destroy_inode)(struct inode *);

        void (*dirty_inode) (struct inode *, int flags);
        int (*write_inode) (struct inode *, struct writeback_control *wbc);
        int (*drop_inode) (struct inode *);
        void (*evict_inode) (struct inode *);
        void (*put_super) (struct super_block *);
        int (*sync_fs)(struct super_block *sb, int wait);
        int (*freeze_super) (struct super_block *);
        int (*freeze_fs) (struct super_block *);
        int (*thaw_super) (struct super_block *);
        int (*unfreeze_fs) (struct super_block *);
        int (*statfs) (struct dentry *, struct kstatfs *);
        int (*remount_fs) (struct super_block *, int *, char *);
        void (*umount_begin) (struct super_block *);

        int (*show_options)(struct seq_file *, struct dentry *);
        int (*show_devname)(struct seq_file *, struct dentry *);
        int (*show_path)(struct seq_file *, struct dentry *);
        int (*show_stats)(struct seq_file *, struct dentry *);
#ifdef CONFIG_QUOTA
        ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
        ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
        struct dquot **(*get_dquots)(struct inode *);
#endif
        int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
        long (*nr_cached_objects)(struct super_block *,
                                  struct shrink_control *);
        long (*free_cached_objects)(struct super_block *,
                                    struct shrink_control *);
};

/*
 * Inode flags - they have no relation to superblock flags now
 */
#define S_SYNC          1       /* Writes are synced at once */
#define S_NOATIME       2       /* Do not update access times */
#define S_APPEND        4       /* Append-only file */
#define S_IMMUTABLE     8       /* Immutable file */
#define S_DEAD          16      /* removed, but still open directory */
#define S_NOQUOTA       32      /* Inode is not counted to quota */
#define S_DIRSYNC       64      /* Directory modifications are synchronous */
#define S_NOCMTIME      128     /* Do not update file c/mtime */
#define S_SWAPFILE      256     /* Do not truncate: swapon got its bmaps */
#define S_PRIVATE       512     /* Inode is fs-internal */
#define S_IMA           1024    /* Inode has an associated IMA struct */
#define S_AUTOMOUNT     2048    /* Automount/referral quasi-directory */
#define S_NOSEC         4096    /* no suid or xattr security attributes */
#ifdef CONFIG_FS_DAX
#define S_DAX           8192    /* Direct Access, avoiding the page cache */
#else
#define S_DAX           0       /* Make all the DAX code disappear */
#endif
#define S_ENCRYPTED     16384   /* Encrypted file (using fs/crypto/) */

/*
 * Note that nosuid etc flags are inode-specific: setting some file-system
 * flags just means all the inodes inherit those flags by default. It might be
 * possible to override it selectively if you really wanted to with some
 * ioctl() that is not currently implemented.
 *
 * Exception: SB_RDONLY is always applied to the entire file system.
 *
 * Unfortunately, it is possible to change a filesystems flags with it mounted
 * with files in use.  This means that all of the inodes will not have their
 * i_flags updated.  Hence, i_flags no longer inherit the superblock mount
 * flags, so these have to be checked separately. -- rmk@arm.uk.linux.org
 */
#define __IS_FLG(inode, flg)    ((inode)->i_sb->s_flags & (flg))

static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags & SB_RDONLY; }
#define IS_RDONLY(inode)        sb_rdonly((inode)->i_sb)
#define IS_SYNC(inode)          (__IS_FLG(inode, SB_SYNCHRONOUS) || \
                                        ((inode)->i_flags & S_SYNC))
#define IS_DIRSYNC(inode)       (__IS_FLG(inode, SB_SYNCHRONOUS|SB_DIRSYNC) || \
                                        ((inode)->i_flags & (S_SYNC|S_DIRSYNC)))
#define IS_MANDLOCK(inode)      __IS_FLG(inode, SB_MANDLOCK)
#define IS_NOATIME(inode)       __IS_FLG(inode, SB_RDONLY|SB_NOATIME)
#define IS_I_VERSION(inode)     __IS_FLG(inode, SB_I_VERSION)

#define IS_NOQUOTA(inode)       ((inode)->i_flags & S_NOQUOTA)
#define IS_APPEND(inode)        ((inode)->i_flags & S_APPEND)
#define IS_IMMUTABLE(inode)     ((inode)->i_flags & S_IMMUTABLE)
#define IS_POSIXACL(inode)      __IS_FLG(inode, SB_POSIXACL)

#define IS_DEADDIR(inode)       ((inode)->i_flags & S_DEAD)
#define IS_NOCMTIME(inode)      ((inode)->i_flags & S_NOCMTIME)
#define IS_SWAPFILE(inode)      ((inode)->i_flags & S_SWAPFILE)
#define IS_PRIVATE(inode)       ((inode)->i_flags & S_PRIVATE)
#define IS_IMA(inode)           ((inode)->i_flags & S_IMA)
#define IS_AUTOMOUNT(inode)     ((inode)->i_flags & S_AUTOMOUNT)
#define IS_NOSEC(inode)         ((inode)->i_flags & S_NOSEC)
#define IS_DAX(inode)           ((inode)->i_flags & S_DAX)
#define IS_ENCRYPTED(inode)     ((inode)->i_flags & S_ENCRYPTED)

#define IS_WHITEOUT(inode)      (S_ISCHR(inode->i_mode) && \
                                 (inode)->i_rdev == WHITEOUT_DEV)

static inline bool HAS_UNMAPPED_ID(struct inode *inode)
{
        return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid);
}

static inline enum rw_hint file_write_hint(struct file *file)
{
        if (file->f_write_hint != WRITE_LIFE_NOT_SET)
                return file->f_write_hint;

        return file_inode(file)->i_write_hint;
}

static inline int iocb_flags(struct file *file);

static inline u16 ki_hint_validate(enum rw_hint hint)
{
        typeof(((struct kiocb *)0)->ki_hint) max_hint = -1;

        if (hint <= max_hint)
                return hint;
        return 0;
}

static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
{
        *kiocb = (struct kiocb) {
                .ki_filp = filp,
                .ki_flags = iocb_flags(filp),
                .ki_hint = ki_hint_validate(file_write_hint(filp)),
                .ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0),
        };
}

/*
 * Inode state bits.  Protected by inode->i_lock
 *
 * Three bits determine the dirty state of the inode, I_DIRTY_SYNC,
 * I_DIRTY_DATASYNC and I_DIRTY_PAGES.
 *
 * Four bits define the lifetime of an inode.  Initially, inodes are I_NEW,
 * until that flag is cleared.  I_WILL_FREE, I_FREEING and I_CLEAR are set at
 * various stages of removing an inode.
 *
 * Two bits are used for locking and completion notification, I_NEW and I_SYNC.
 *
 * I_DIRTY_SYNC         Inode is dirty, but doesn't have to be written on
 *                      fdatasync().  i_atime is the usual cause.
 * I_DIRTY_DATASYNC     Data-related inode changes pending. We keep track of
 *                      these changes separately from I_DIRTY_SYNC so that we
 *                      don't have to write inode on fdatasync() when only
 *                      mtime has changed in it.
 * I_DIRTY_PAGES        Inode has dirty pages.  Inode itself may be clean.
 * I_NEW                Serves as both a mutex and completion notification.
 *                      New inodes set I_NEW.  If two processes both create
 *                      the same inode, one of them will release its inode and
 *                      wait for I_NEW to be released before returning.
 *                      Inodes in I_WILL_FREE, I_FREEING or I_CLEAR state can
 *                      also cause waiting on I_NEW, without I_NEW actually
 *                      being set.  find_inode() uses this to prevent returning
 *                      nearly-dead inodes.
 * I_WILL_FREE          Must be set when calling write_inode_now() if i_count
 *                      is zero.  I_FREEING must be set when I_WILL_FREE is
 *                      cleared.
 * I_FREEING            Set when inode is about to be freed but still has dirty
 *                      pages or buffers attached or the inode itself is still
 *                      dirty.
 * I_CLEAR              Added by clear_inode().  In this state the inode is
 *                      clean and can be destroyed.  Inode keeps I_FREEING.
 *
 *                      Inodes that are I_WILL_FREE, I_FREEING or I_CLEAR are
 *                      prohibited for many purposes.  iget() must wait for
 *                      the inode to be completely released, then create it
 *                      anew.  Other functions will just ignore such inodes,
 *                      if appropriate.  I_NEW is used for waiting.
 *
 * I_SYNC               Writeback of inode is running. The bit is set during
 *                      data writeback, and cleared with a wakeup on the bit
 *                      address once it is done. The bit is also used to pin
 *                      the inode in memory for flusher thread.
 *
 * I_REFERENCED         Marks the inode as recently references on the LRU list.
 *
 * I_DIO_WAKEUP         Never set.  Only used as a key for wait_on_bit().
 *
 * I_WB_SWITCH          Cgroup bdi_writeback switching in progress.  Used to
 *                      synchronize competing switching instances and to tell
 *                      wb stat updates to grab the i_pages lock.  See
 *                      inode_switch_wb_work_fn() for details.
 *
 * I_OVL_INUSE          Used by overlayfs to get exclusive ownership on upper
 *                      and work dirs among overlayfs mounts.
 *
 * I_CREATING           New object's inode in the middle of setting up.
 *
 * I_SYNC_QUEUED        Inode is queued in b_io or b_more_io writeback lists.
 *                      Used to detect that mark_inode_dirty() should not move
 *                      inode between dirty lists.
 *
 * Q: What is the difference between I_WILL_FREE and I_FREEING?
 */
#define I_DIRTY_SYNC            (1 << 0)
#define I_DIRTY_DATASYNC        (1 << 1)
#define I_DIRTY_PAGES           (1 << 2)
#define __I_NEW                 3
#define I_NEW                   (1 << __I_NEW)
#define I_WILL_FREE             (1 << 4)
#define I_FREEING               (1 << 5)
#define I_CLEAR                 (1 << 6)
#define __I_SYNC                7
#define I_SYNC                  (1 << __I_SYNC)
#define I_REFERENCED            (1 << 8)
#define __I_DIO_WAKEUP          9
#define I_DIO_WAKEUP            (1 << __I_DIO_WAKEUP)
#define I_LINKABLE              (1 << 10)
#define I_DIRTY_TIME            (1 << 11)
#define I_WB_SWITCH             (1 << 13)
#define I_OVL_INUSE             (1 << 14)
#define I_CREATING              (1 << 15)
#define I_SYNC_QUEUED           (1 << 17)

#define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
#define I_DIRTY (I_DIRTY_INODE | I_DIRTY_PAGES)
#define I_DIRTY_ALL (I_DIRTY | I_DIRTY_TIME)

extern void __mark_inode_dirty(struct inode *, int);
static inline void mark_inode_dirty(struct inode *inode)
{
        __mark_inode_dirty(inode, I_DIRTY);
}

static inline void mark_inode_dirty_sync(struct inode *inode)
{
        __mark_inode_dirty(inode, I_DIRTY_SYNC);
}

extern void inc_nlink(struct inode *inode);
extern void drop_nlink(struct inode *inode);
extern void clear_nlink(struct inode *inode);
extern void set_nlink(struct inode *inode, unsigned int nlink);

static inline void inode_inc_link_count(struct inode *inode)
{
        inc_nlink(inode);
        mark_inode_dirty(inode);
}

static inline void inode_dec_link_count(struct inode *inode)
{
        drop_nlink(inode);
        mark_inode_dirty(inode);
}

enum file_time_flags {
        S_ATIME = 1,
        S_MTIME = 2,
        S_CTIME = 4,
        S_VERSION = 8,
};

extern bool atime_needs_update(const struct path *, struct inode *);
extern void touch_atime(const struct path *);
static inline void file_accessed(struct file *file)
{
        if (!(file->f_flags & O_NOATIME))
                touch_atime(&file->f_path);
}

int sync_inode(struct inode *inode, struct writeback_control *wbc);
int sync_inode_metadata(struct inode *inode, int wait);

struct file_system_type {
        const char *name;
        int fs_flags;
#define FS_REQUIRES_DEV         1 
#define FS_BINARY_MOUNTDATA     2
#define FS_HAS_SUBTYPE          4
#define FS_USERNS_MOUNT         8       /* Can be mounted by userns root */
#define FS_RENAME_DOES_D_MOVE   32768   /* FS will handle d_move() during rename() internally. */
        struct dentry *(*mount) (struct file_system_type *, int,
                       const char *, void *);
        void (*kill_sb) (struct super_block *);
        struct module *owner;
        struct file_system_type * next;
        struct hlist_head fs_supers;

        struct lock_class_key s_lock_key;
        struct lock_class_key s_umount_key;
        struct lock_class_key s_vfs_rename_key;
        struct lock_class_key s_writers_key[SB_FREEZE_LEVELS];

        struct lock_class_key i_lock_key;
        struct lock_class_key i_mutex_key;
        struct lock_class_key i_mutex_dir_key;
};

#define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME)

extern struct dentry *mount_ns(struct file_system_type *fs_type,
        int flags, void *data, void *ns, struct user_namespace *user_ns,
        int (*fill_super)(struct super_block *, void *, int));
#ifdef CONFIG_BLOCK
extern struct dentry *mount_bdev(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data,
        int (*fill_super)(struct super_block *, void *, int));
#else
static inline struct dentry *mount_bdev(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data,
        int (*fill_super)(struct super_block *, void *, int))
{
        return ERR_PTR(-ENODEV);
}
#endif
extern struct dentry *mount_single(struct file_system_type *fs_type,
        int flags, void *data,
        int (*fill_super)(struct super_block *, void *, int));
extern struct dentry *mount_nodev(struct file_system_type *fs_type,
        int flags, void *data,
        int (*fill_super)(struct super_block *, void *, int));
extern struct dentry *mount_subtree(struct vfsmount *mnt, const char *path);
void generic_shutdown_super(struct super_block *sb);
#ifdef CONFIG_BLOCK
void kill_block_super(struct super_block *sb);
#else
static inline void kill_block_super(struct super_block *sb)
{
        BUG();
}
#endif
void kill_anon_super(struct super_block *sb);
void kill_litter_super(struct super_block *sb);
void deactivate_super(struct super_block *sb);
void deactivate_locked_super(struct super_block *sb);
int set_anon_super(struct super_block *s, void *data);
int get_anon_bdev(dev_t *);
void free_anon_bdev(dev_t);
struct super_block *sget_userns(struct file_system_type *type,
                        int (*test)(struct super_block *,void *),
                        int (*set)(struct super_block *,void *),
                        int flags, struct user_namespace *user_ns,
                        void *data);
struct super_block *sget(struct file_system_type *type,
                        int (*test)(struct super_block *,void *),
                        int (*set)(struct super_block *,void *),
                        int flags, void *data);
extern struct dentry *mount_pseudo_xattr(struct file_system_type *, char *,
                                         const struct super_operations *ops,
                                         const struct xattr_handler **xattr,
                                         const struct dentry_operations *dops,
                                         unsigned long);

static inline struct dentry *
mount_pseudo(struct file_system_type *fs_type, char *name,
             const struct super_operations *ops,
             const struct dentry_operations *dops, unsigned long magic)
{
        return mount_pseudo_xattr(fs_type, name, ops, NULL, dops, magic);
}

/* Alas, no aliases. Too much hassle with bringing module.h everywhere */
#define fops_get(fops) \
        (((fops) && try_module_get((fops)->owner) ? (fops) : NULL))
#define fops_put(fops) \
        do { if (fops) module_put((fops)->owner); } while(0)
/*
 * This one is to be used *ONLY* from ->open() instances.
 * fops must be non-NULL, pinned down *and* module dependencies
 * should be sufficient to pin the caller down as well.
 */
#define replace_fops(f, fops) \
        do {    \
                struct file *__file = (f); \
                fops_put(__file->f_op); \
                BUG_ON(!(__file->f_op = (fops))); \
        } while(0)

extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);
extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data);
#define kern_mount(type) kern_mount_data(type, NULL)
extern void kern_unmount(struct vfsmount *mnt);
extern int may_umount_tree(struct vfsmount *);
extern int may_umount(struct vfsmount *);
extern long do_mount(const char *, const char __user *,
                     const char *, unsigned long, void *);
extern struct vfsmount *collect_mounts(const struct path *);
extern void drop_collected_mounts(struct vfsmount *);
extern int iterate_mounts(int (*)(struct vfsmount *, void *), void *,
                          struct vfsmount *);
extern int vfs_statfs(const struct path *, struct kstatfs *);
extern int user_statfs(const char __user *, struct kstatfs *);
extern int fd_statfs(int, struct kstatfs *);
extern int freeze_super(struct super_block *super);
extern int thaw_super(struct super_block *super);
extern bool our_mnt(struct vfsmount *mnt);
extern __printf(2, 3)
int super_setup_bdi_name(struct super_block *sb, char *fmt, ...);
extern int super_setup_bdi(struct super_block *sb);

extern int current_umask(void);

extern void ihold(struct inode * inode);
extern void iput(struct inode *);
extern int generic_update_time(struct inode *, struct timespec64 *, int);

/* /sys/fs */
extern struct kobject *fs_kobj;

#define MAX_RW_COUNT (INT_MAX & PAGE_MASK)

#ifdef CONFIG_MANDATORY_FILE_LOCKING
extern int locks_mandatory_locked(struct file *);
extern int locks_mandatory_area(struct inode *, struct file *, loff_t, loff_t, unsigned char);

/*
 * Candidates for mandatory locking have the setgid bit set
 * but no group execute bit -  an otherwise meaningless combination.
 */

static inline int __mandatory_lock(struct inode *ino)
{
        return (ino->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID;
}

/*
 * ... and these candidates should be on SB_MANDLOCK mounted fs,
 * otherwise these will be advisory locks
 */

static inline int mandatory_lock(struct inode *ino)
{
        return IS_MANDLOCK(ino) && __mandatory_lock(ino);
}

static inline int locks_verify_locked(struct file *file)
{
        if (mandatory_lock(locks_inode(file)))
                return locks_mandatory_locked(file);
        return 0;
}

static inline int locks_verify_truncate(struct inode *inode,
                                    struct file *f,
                                    loff_t size)
{
        if (!inode->i_flctx || !mandatory_lock(inode))
                return 0;

        if (size < inode->i_size) {
                return locks_mandatory_area(inode, f, size, inode->i_size - 1,
                                F_WRLCK);
        } else {
                return locks_mandatory_area(inode, f, inode->i_size, size - 1,
                                F_WRLCK);
        }
}

#else /* !CONFIG_MANDATORY_FILE_LOCKING */

static inline int locks_mandatory_locked(struct file *file)
{
        return 0;
}

static inline int locks_mandatory_area(struct inode *inode, struct file *filp,
                                       loff_t start, loff_t end, unsigned char type)
{
        return 0;
}

static inline int __mandatory_lock(struct inode *inode)
{
        return 0;
}

static inline int mandatory_lock(struct inode *inode)
{
        return 0;
}

static inline int locks_verify_locked(struct file *file)
{
        return 0;
}

static inline int locks_verify_truncate(struct inode *inode, struct file *filp,
                                        size_t size)
{
        return 0;
}

#endif /* CONFIG_MANDATORY_FILE_LOCKING */


#ifdef CONFIG_FILE_LOCKING
static inline int break_lease(struct inode *inode, unsigned int mode)
{
        /*
         * Since this check is lockless, we must ensure that any refcounts
         * taken are done before checking i_flctx->flc_lease. Otherwise, we
         * could end up racing with tasks trying to set a new lease on this
         * file.
         */
        smp_mb();
        if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
                return __break_lease(inode, mode, FL_LEASE);
        return 0;
}

static inline int break_deleg(struct inode *inode, unsigned int mode)
{
        /*
         * Since this check is lockless, we must ensure that any refcounts
         * taken are done before checking i_flctx->flc_lease. Otherwise, we
         * could end up racing with tasks trying to set a new lease on this
         * file.
         */
        smp_mb();
        if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
                return __break_lease(inode, mode, FL_DELEG);
        return 0;
}

static inline int try_break_deleg(struct inode *inode, struct inode **delegated_inode)
{
        int ret;

        ret = break_deleg(inode, O_WRONLY|O_NONBLOCK);
        if (ret == -EWOULDBLOCK && delegated_inode) {
                *delegated_inode = inode;
                ihold(inode);
        }
        return ret;
}

static inline int break_deleg_wait(struct inode **delegated_inode)
{
        int ret;

        ret = break_deleg(*delegated_inode, O_WRONLY);
        iput(*delegated_inode);
        *delegated_inode = NULL;
        return ret;
}

static inline int break_layout(struct inode *inode, bool wait)
{
        smp_mb();
        if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
                return __break_lease(inode,
                                wait ? O_WRONLY : O_WRONLY | O_NONBLOCK,
                                FL_LAYOUT);
        return 0;
}

#else /* !CONFIG_FILE_LOCKING */
static inline int break_lease(struct inode *inode, unsigned int mode)
{
        return 0;
}

static inline int break_deleg(struct inode *inode, unsigned int mode)
{
        return 0;
}

static inline int try_break_deleg(struct inode *inode, struct inode **delegated_inode)
{
        return 0;
}

static inline int break_deleg_wait(struct inode **delegated_inode)
{
        BUG();
        return 0;
}

static inline int break_layout(struct inode *inode, bool wait)
{
        return 0;
}

#endif /* CONFIG_FILE_LOCKING */

/* fs/open.c */
struct audit_names;
struct filename {
        const char              *name;  /* pointer to actual string */
        const __user char       *uptr;  /* original userland pointer */
        int                     refcnt;
        struct audit_names      *aname;
        const char              iname[];
};

extern long vfs_truncate(const struct path *, loff_t);
extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
                       struct file *filp);
extern int vfs_fallocate(struct file *file, int mode, loff_t offset,
                        loff_t len);
extern long do_sys_open(int dfd, const char __user *filename, int flags,
                        umode_t mode);
extern struct file *file_open_name(struct filename *, int, umode_t);
extern struct file *filp_open(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
                                   const char *, int, umode_t);
extern struct file * dentry_open(const struct path *, int, const struct cred *);
extern struct file * open_with_fake_path(const struct path *, int,
                                         struct inode*, const struct cred *);
static inline struct file *file_clone_open(struct file *file)
{
        return dentry_open(&file->f_path, file->f_flags, file->f_cred);
}
extern int filp_close(struct file *, fl_owner_t id);

extern struct filename *getname_flags(const char __user *, int, int *);
extern struct filename *getname(const char __user *);
extern struct filename *getname_kernel(const char *);
extern void putname(struct filename *name);

extern int finish_open(struct file *file, struct dentry *dentry,
                        int (*open)(struct inode *, struct file *));
extern int finish_no_open(struct file *file, struct dentry *dentry);

/* fs/ioctl.c */

extern int ioctl_preallocate(struct file *filp, void __user *argp);

/* fs/dcache.c */
extern void __init vfs_caches_init_early(void);
extern void __init vfs_caches_init(void);

extern struct kmem_cache *names_cachep;

#define __getname()             kmem_cache_alloc(names_cachep, GFP_KERNEL)
#define __putname(name)         kmem_cache_free(names_cachep, (void *)(name))

#ifdef CONFIG_BLOCK
extern int register_blkdev(unsigned int, const char *);
extern void unregister_blkdev(unsigned int, const char *);
extern void bdev_unhash_inode(dev_t dev);
extern struct block_device *bdget(dev_t);
extern struct block_device *bdgrab(struct block_device *bdev);
extern void bd_set_size(struct block_device *, loff_t size);
extern void bd_forget(struct inode *inode);
extern void bdput(struct block_device *);
extern void invalidate_bdev(struct block_device *);
extern void iterate_bdevs(void (*)(struct block_device *, void *), void *);
extern int sync_blockdev(struct block_device *bdev);
extern void kill_bdev(struct block_device *);
extern struct super_block *freeze_bdev(struct block_device *);
extern void emergency_thaw_all(void);
extern void emergency_thaw_bdev(struct super_block *sb);
extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
extern int fsync_bdev(struct block_device *);

extern struct super_block *blockdev_superblock;

static inline bool sb_is_blkdev_sb(struct super_block *sb)
{
        return sb == blockdev_superblock;
}
#else
static inline void bd_forget(struct inode *inode) {}
static inline int sync_blockdev(struct block_device *bdev) { return 0; }
static inline void kill_bdev(struct block_device *bdev) {}
static inline void invalidate_bdev(struct block_device *bdev) {}

static inline struct super_block *freeze_bdev(struct block_device *sb)
{
        return NULL;
}

static inline int thaw_bdev(struct block_device *bdev, struct super_block *sb)
{
        return 0;
}

static inline int emergency_thaw_bdev(struct super_block *sb)
{
        return 0;
}

static inline void iterate_bdevs(void (*f)(struct block_device *, void *), void *arg)
{
}

static inline bool sb_is_blkdev_sb(struct super_block *sb)
{
        return false;
}
#endif
extern int sync_filesystem(struct super_block *);
extern const struct file_operations def_blk_fops;
extern const struct file_operations def_chr_fops;
#ifdef CONFIG_BLOCK
extern int ioctl_by_bdev(struct block_device *, unsigned, unsigned long);
extern int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);
extern long compat_blkdev_ioctl(struct file *, unsigned, unsigned long);
extern int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder);
extern struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
                                               void *holder);
extern struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode,
                                              void *holder);
extern void blkdev_put(struct block_device *bdev, fmode_t mode);
extern int __blkdev_reread_part(struct block_device *bdev);
extern int blkdev_reread_part(struct block_device *bdev);

#ifdef CONFIG_SYSFS
extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
extern void bd_unlink_disk_holder(struct block_device *bdev,
                                  struct gendisk *disk);
#else
static inline int bd_link_disk_holder(struct block_device *bdev,
                                      struct gendisk *disk)
{
        return 0;
}
static inline void bd_unlink_disk_holder(struct block_device *bdev,
                                         struct gendisk *disk)
{
}
#endif
#endif

/* fs/char_dev.c */
#define CHRDEV_MAJOR_MAX 512
/* Marks the bottom of the first segment of free char majors */
#define CHRDEV_MAJOR_DYN_END 234
/* Marks the top and bottom of the second segment of free char majors */
#define CHRDEV_MAJOR_DYN_EXT_START 511
#define CHRDEV_MAJOR_DYN_EXT_END 384

extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *);
extern int register_chrdev_region(dev_t, unsigned, const char *);
extern int __register_chrdev(unsigned int major, unsigned int baseminor,
                             unsigned int count, const char *name,
                             const struct file_operations *fops);
extern void __unregister_chrdev(unsigned int major, unsigned int baseminor,
                                unsigned int count, const char *name);
extern void unregister_chrdev_region(dev_t, unsigned);
extern void chrdev_show(struct seq_file *,off_t);

static inline int register_chrdev(unsigned int major, const char *name,
                                  const struct file_operations *fops)
{
        return __register_chrdev(major, 0, 256, name, fops);
}

static inline void unregister_chrdev(unsigned int major, const char *name)
{
        __unregister_chrdev(major, 0, 256, name);
}

/* fs/block_dev.c */
#define BDEVNAME_SIZE   32      /* Largest string for a blockdev identifier */
#define BDEVT_SIZE      10      /* Largest string for MAJ:MIN for blkdev */

#ifdef CONFIG_BLOCK
#define BLKDEV_MAJOR_MAX        512
extern const char *__bdevname(dev_t, char *buffer);
extern const char *bdevname(struct block_device *bdev, char *buffer);
extern struct block_device *lookup_bdev(const char *);
extern void blkdev_show(struct seq_file *,off_t);

#else
#define BLKDEV_MAJOR_MAX        0
#endif

extern void init_special_inode(struct inode *, umode_t, dev_t);

/* Invalid inode operations -- fs/bad_inode.c */
extern void make_bad_inode(struct inode *);
extern bool is_bad_inode(struct inode *);

#ifdef CONFIG_BLOCK
extern void check_disk_size_change(struct gendisk *disk,
                struct block_device *bdev, bool verbose);
extern int revalidate_disk(struct gendisk *);
extern int check_disk_change(struct block_device *);
extern int __invalidate_device(struct block_device *, bool);
extern int invalidate_partition(struct gendisk *, int);
#endif
unsigned long invalidate_mapping_pages(struct address_space *mapping,
                                        pgoff_t start, pgoff_t end);

static inline void invalidate_remote_inode(struct inode *inode)
{
        if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
            S_ISLNK(inode->i_mode))
                invalidate_mapping_pages(inode->i_mapping, 0, -1);
}
extern int invalidate_inode_pages2(struct address_space *mapping);
extern int invalidate_inode_pages2_range(struct address_space *mapping,
                                         pgoff_t start, pgoff_t end);
extern int write_inode_now(struct inode *, int);
extern int filemap_fdatawrite(struct address_space *);
extern int filemap_flush(struct address_space *);
extern int filemap_fdatawait_keep_errors(struct address_space *mapping);
extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
                                   loff_t lend);
extern int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
                loff_t start_byte, loff_t end_byte);

static inline int filemap_fdatawait(struct address_space *mapping)
{
        return filemap_fdatawait_range(mapping, 0, LLONG_MAX);
}

extern bool filemap_range_has_page(struct address_space *, loff_t lstart,
                                  loff_t lend);
extern int filemap_write_and_wait(struct address_space *mapping);
extern int filemap_write_and_wait_range(struct address_space *mapping,
                                        loff_t lstart, loff_t lend);
extern int __filemap_fdatawrite_range(struct address_space *mapping,
                                loff_t start, loff_t end, int sync_mode);
extern int filemap_fdatawrite_range(struct address_space *mapping,
                                loff_t start, loff_t end);
extern int filemap_check_errors(struct address_space *mapping);
extern void __filemap_set_wb_err(struct address_space *mapping, int err);

extern int __must_check file_fdatawait_range(struct file *file, loff_t lstart,
                                                loff_t lend);
extern int __must_check file_check_and_advance_wb_err(struct file *file);
extern int __must_check file_write_and_wait_range(struct file *file,
                                                loff_t start, loff_t end);

static inline int file_write_and_wait(struct file *file)
{
        return file_write_and_wait_range(file, 0, LLONG_MAX);
}

/**
 * filemap_set_wb_err - set a writeback error on an address_space
 * @mapping: mapping in which to set writeback error
 * @err: error to be set in mapping
 *
 * When writeback fails in some way, we must record that error so that
 * userspace can be informed when fsync and the like are called.  We endeavor
 * to report errors on any file that was open at the time of the error.  Some
 * internal callers also need to know when writeback errors have occurred.
 *
 * When a writeback error occurs, most filesystems will want to call
 * filemap_set_wb_err to record the error in the mapping so that it will be
 * automatically reported whenever fsync is called on the file.
 */
static inline void filemap_set_wb_err(struct address_space *mapping, int err)
{
        /* Fastpath for common case of no error */
        if (unlikely(err))
                __filemap_set_wb_err(mapping, err);
}

/**
 * filemap_check_wb_error - has an error occurred since the mark was sampled?
 * @mapping: mapping to check for writeback errors
 * @since: previously-sampled errseq_t
 *
 * Grab the errseq_t value from the mapping, and see if it has changed "since"
 * the given value was sampled.
 *
 * If it has then report the latest error set, otherwise return 0.
 */
static inline int filemap_check_wb_err(struct address_space *mapping,
                                        errseq_t since)
{
        return errseq_check(&mapping->wb_err, since);
}

/**
 * filemap_sample_wb_err - sample the current errseq_t to test for later errors
 * @mapping: mapping to be sampled
 *
 * Writeback errors are always reported relative to a particular sample point
 * in the past. This function provides those sample points.
 */
static inline errseq_t filemap_sample_wb_err(struct address_space *mapping)
{
        return errseq_sample(&mapping->wb_err);
}

extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end,
                           int datasync);
extern int vfs_fsync(struct file *file, int datasync);

/*
 * Sync the bytes written if this was a synchronous write.  Expect ki_pos
 * to already be updated for the write, and will return either the amount
 * of bytes passed in, or an error if syncing the file failed.
 */
static inline ssize_t generic_write_sync(struct kiocb *iocb, ssize_t count)
{
        if (iocb->ki_flags & IOCB_DSYNC) {
                int ret = vfs_fsync_range(iocb->ki_filp,
                                iocb->ki_pos - count, iocb->ki_pos - 1,
                                (iocb->ki_flags & IOCB_SYNC) ? 0 : 1);
                if (ret)
                        return ret;
        }

        return count;
}

extern void emergency_sync(void);
extern void emergency_remount(void);
#ifdef CONFIG_BLOCK
extern sector_t bmap(struct inode *, sector_t);
#endif
extern int notify_change(struct dentry *, struct iattr *, struct inode **);
extern int inode_permission(struct inode *, int);
extern int generic_permission(struct inode *, int);
extern int __check_sticky(struct inode *dir, struct inode *inode);

static inline bool execute_ok(struct inode *inode)
{
        return (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode);
}

static inline void file_start_write(struct file *file)
{
        if (!S_ISREG(file_inode(file)->i_mode))
                return;
        __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, true);
}

static inline bool file_start_write_trylock(struct file *file)
{
        if (!S_ISREG(file_inode(file)->i_mode))
                return true;
        return __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, false);
}

static inline void file_end_write(struct file *file)
{
        if (!S_ISREG(file_inode(file)->i_mode))
                return;
        __sb_end_write(file_inode(file)->i_sb, SB_FREEZE_WRITE);
}

/*
 * get_write_access() gets write permission for a file.
 * put_write_access() releases this write permission.
 * This is used for regular files.
 * We cannot support write (and maybe mmap read-write shared) accesses and
 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
 * can have the following values:
 * 0: no writers, no VM_DENYWRITE mappings
 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
 * > 0: (i_writecount) users are writing to the file.
 *
 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
 * except for the cases where we don't hold i_writecount yet. Then we need to
 * use {get,deny}_write_access() - these functions check the sign and refuse
 * to do the change if sign is wrong.
 */
static inline int get_write_access(struct inode *inode)
{
        return atomic_inc_unless_negative(&inode->i_writecount) ? 0 : -ETXTBSY;
}
static inline int deny_write_access(struct file *file)
{
        struct inode *inode = file_inode(file);
        return atomic_dec_unless_positive(&inode->i_writecount) ? 0 : -ETXTBSY;
}
static inline void put_write_access(struct inode * inode)
{
        atomic_dec(&inode->i_writecount);
}
static inline void allow_write_access(struct file *file)
{
        if (file)
                atomic_inc(&file_inode(file)->i_writecount);
}
static inline bool inode_is_open_for_write(const struct inode *inode)
{
        return atomic_read(&inode->i_writecount) > 0;
}

#ifdef CONFIG_IMA
static inline void i_readcount_dec(struct inode *inode)
{
        BUG_ON(!atomic_read(&inode->i_readcount));
        atomic_dec(&inode->i_readcount);
}
static inline void i_readcount_inc(struct inode *inode)
{
        atomic_inc(&inode->i_readcount);
}
#else
static inline void i_readcount_dec(struct inode *inode)
{
        return;
}
static inline void i_readcount_inc(struct inode *inode)
{
        return;
}
#endif
extern int do_pipe_flags(int *, int);

#define __kernel_read_file_id(id) \
        id(UNKNOWN, unknown)            \
        id(FIRMWARE, firmware)          \
        id(FIRMWARE_PREALLOC_BUFFER, firmware)  \
        id(MODULE, kernel-module)               \
        id(KEXEC_IMAGE, kexec-image)            \
        id(KEXEC_INITRAMFS, kexec-initramfs)    \
        id(POLICY, security-policy)             \
        id(X509_CERTIFICATE, x509-certificate)  \
        id(MAX_ID, )

#define __fid_enumify(ENUM, dummy) READING_ ## ENUM,
#define __fid_stringify(dummy, str) #str,

enum kernel_read_file_id {
        __kernel_read_file_id(__fid_enumify)
};

static const char * const kernel_read_file_str[] = {
        __kernel_read_file_id(__fid_stringify)
};

static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id)
{
        if ((unsigned)id >= READING_MAX_ID)
                return kernel_read_file_str[READING_UNKNOWN];

        return kernel_read_file_str[id];
}

extern int kernel_read_file(struct file *, void **, loff_t *, loff_t,
                            enum kernel_read_file_id);
extern int kernel_read_file_from_path(const char *, void **, loff_t *, loff_t,
                                      enum kernel_read_file_id);
extern int kernel_read_file_from_fd(int, void **, loff_t *, loff_t,
                                    enum kernel_read_file_id);
extern ssize_t kernel_read(struct file *, void *, size_t, loff_t *);
extern ssize_t kernel_write(struct file *, const void *, size_t, loff_t *);
extern ssize_t __kernel_write(struct file *, const void *, size_t, loff_t *);
extern struct file * open_exec(const char *);
 
/* fs/dcache.c -- generic fs support functions */
extern bool is_subdir(struct dentry *, struct dentry *);
extern bool path_is_under(const struct path *, const struct path *);

extern char *file_path(struct file *, char *, int);

#include <linux/err.h>

/* needed for stackable file system support */
extern loff_t default_llseek(struct file *file, loff_t offset, int whence);

extern loff_t vfs_llseek(struct file *file, loff_t offset, int whence);

extern int inode_init_always(struct super_block *, struct inode *);
extern void inode_init_once(struct inode *);
extern void address_space_init_once(struct address_space *mapping);
extern struct inode * igrab(struct inode *);
extern ino_t iunique(struct super_block *, ino_t);
extern int inode_needs_sync(struct inode *inode);
extern int generic_delete_inode(struct inode *inode);
static inline int generic_drop_inode(struct inode *inode)
{
        return !inode->i_nlink || inode_unhashed(inode);
}

extern struct inode *ilookup5_nowait(struct super_block *sb,
                unsigned long hashval, int (*test)(struct inode *, void *),
                void *data);
extern struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
                int (*test)(struct inode *, void *), void *data);
extern struct inode *ilookup(struct super_block *sb, unsigned long ino);

extern struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
                int (*test)(struct inode *, void *),
                int (*set)(struct inode *, void *),
                void *data);
extern struct inode * iget5_locked(struct super_block *, unsigned long, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *);
extern struct inode * iget_locked(struct super_block *, unsigned long);
extern struct inode *find_inode_nowait(struct super_block *,
                                       unsigned long,
                                       int (*match)(struct inode *,
                                                    unsigned long, void *),
                                       void *data);
extern int insert_inode_locked4(struct inode *, unsigned long, int (*test)(struct inode *, void *), void *);
extern int insert_inode_locked(struct inode *);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void lockdep_annotate_inode_mutex_key(struct inode *inode);
#else
static inline void lockdep_annotate_inode_mutex_key(struct inode *inode) { };
#endif
extern void unlock_new_inode(struct inode *);
extern void discard_new_inode(struct inode *);
extern unsigned int get_next_ino(void);
extern void evict_inodes(struct super_block *sb);

extern void __iget(struct inode * inode);
extern void iget_failed(struct inode *);
extern void clear_inode(struct inode *);
extern void __destroy_inode(struct inode *);
extern struct inode *new_inode_pseudo(struct super_block *sb);
extern struct inode *new_inode(struct super_block *sb);
extern void free_inode_nonrcu(struct inode *inode);
extern int should_remove_suid(struct dentry *);
extern int file_remove_privs(struct file *);

extern void __insert_inode_hash(struct inode *, unsigned long hashval);
static inline void insert_inode_hash(struct inode *inode)
{
        __insert_inode_hash(inode, inode->i_ino);
}

extern void __remove_inode_hash(struct inode *);
static inline void remove_inode_hash(struct inode *inode)
{
        if (!inode_unhashed(inode) && !hlist_fake(&inode->i_hash))
                __remove_inode_hash(inode);
}

extern void inode_sb_list_add(struct inode *inode);

#ifdef CONFIG_BLOCK
extern int bdev_read_only(struct block_device *);
#endif
extern int set_blocksize(struct block_device *, int);
extern int sb_set_blocksize(struct super_block *, int);
extern int sb_min_blocksize(struct super_block *, int);

extern int generic_file_mmap(struct file *, struct vm_area_struct *);
extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);
extern ssize_t generic_file_direct_write(struct kiocb *, struct iov_iter *);
extern ssize_t generic_perform_write(struct file *, struct iov_iter *, loff_t);

ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
                rwf_t flags);
ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
                rwf_t flags);

/* fs/block_dev.c */
extern ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to);
extern ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from);
extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
                        int datasync);
extern void block_sync_page(struct page *page);

/* fs/splice.c */
extern ssize_t generic_file_splice_read(struct file *, loff_t *,
                struct pipe_inode_info *, size_t, unsigned int);
extern ssize_t iter_file_splice_write(struct pipe_inode_info *,
                struct file *, loff_t *, size_t, unsigned int);
extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
                struct file *out, loff_t *, size_t len, unsigned int flags);
extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
                loff_t *opos, size_t len, unsigned int flags);


extern void
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
extern loff_t noop_llseek(struct file *file, loff_t offset, int whence);
extern loff_t no_llseek(struct file *file, loff_t offset, int whence);
extern loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize);
extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
                int whence, loff_t maxsize, loff_t eof);
extern loff_t fixed_size_llseek(struct file *file, loff_t offset,
                int whence, loff_t size);
extern loff_t no_seek_end_llseek_size(struct file *, loff_t, int, loff_t);
extern loff_t no_seek_end_llseek(struct file *, loff_t, int);
extern int generic_file_open(struct inode * inode, struct file * filp);
extern int nonseekable_open(struct inode * inode, struct file * filp);
extern int stream_open(struct inode * inode, struct file * filp);

#ifdef CONFIG_BLOCK
typedef void (dio_submit_t)(struct bio *bio, struct inode *inode,
                            loff_t file_offset);

enum {
        /* need locking between buffered and direct access */
        DIO_LOCKING     = 0x01,

        /* filesystem does not support filling holes */
        DIO_SKIP_HOLES  = 0x02,
};

void dio_end_io(struct bio *bio);
void dio_warn_stale_pagecache(struct file *filp);

ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
                             struct block_device *bdev, struct iov_iter *iter,
                             get_block_t get_block,
                             dio_iodone_t end_io, dio_submit_t submit_io,
                             int flags);

static inline ssize_t blockdev_direct_IO(struct kiocb *iocb,
                                         struct inode *inode,
                                         struct iov_iter *iter,
                                         get_block_t get_block)
{
        return __blockdev_direct_IO(iocb, inode, inode->i_sb->s_bdev, iter,
                        get_block, NULL, NULL, DIO_LOCKING | DIO_SKIP_HOLES);
}
#endif

void inode_dio_wait(struct inode *inode);

/*
 * inode_dio_begin - signal start of a direct I/O requests
 * @inode: inode the direct I/O happens on
 *
 * This is called once we've finished processing a direct I/O request,
 * and is used to wake up callers waiting for direct I/O to be quiesced.
 */
static inline void inode_dio_begin(struct inode *inode)
{
        atomic_inc(&inode->i_dio_count);
}

/*
 * inode_dio_end - signal finish of a direct I/O requests
 * @inode: inode the direct I/O happens on
 *
 * This is called once we've finished processing a direct I/O request,
 * and is used to wake up callers waiting for direct I/O to be quiesced.
 */
static inline void inode_dio_end(struct inode *inode)
{
        if (atomic_dec_and_test(&inode->i_dio_count))
                wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
}

extern void inode_set_flags(struct inode *inode, unsigned int flags,
                            unsigned int mask);

extern const struct file_operations generic_ro_fops;

#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))

extern int readlink_copy(char __user *, int, const char *);
extern int page_readlink(struct dentry *, char __user *, int);
extern const char *page_get_link(struct dentry *, struct inode *,
                                 struct delayed_call *);
extern void page_put_link(void *);
extern int __page_symlink(struct inode *inode, const char *symname, int len,
                int nofs);
extern int page_symlink(struct inode *inode, const char *symname, int len);
extern const struct inode_operations page_symlink_inode_operations;
extern void kfree_link(void *);
extern void generic_fillattr(struct inode *, struct kstat *);
extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);
extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int);
void __inode_add_bytes(struct inode *inode, loff_t bytes);
void inode_add_bytes(struct inode *inode, loff_t bytes);
void __inode_sub_bytes(struct inode *inode, loff_t bytes);
void inode_sub_bytes(struct inode *inode, loff_t bytes);
static inline loff_t __inode_get_bytes(struct inode *inode)
{
        return (((loff_t)inode->i_blocks) << 9) + inode->i_bytes;
}
loff_t inode_get_bytes(struct inode *inode);
void inode_set_bytes(struct inode *inode, loff_t bytes);
const char *simple_get_link(struct dentry *, struct inode *,
                            struct delayed_call *);
extern const struct inode_operations simple_symlink_inode_operations;

extern int iterate_dir(struct file *, struct dir_context *);

extern int vfs_statx(int, const char __user *, int, struct kstat *, u32);
extern int vfs_statx_fd(unsigned int, struct kstat *, u32, unsigned int);

static inline int vfs_stat(const char __user *filename, struct kstat *stat)
{
        return vfs_statx(AT_FDCWD, filename, AT_NO_AUTOMOUNT,
                         stat, STATX_BASIC_STATS);
}
static inline int vfs_lstat(const char __user *name, struct kstat *stat)
{
        return vfs_statx(AT_FDCWD, name, AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT,
                         stat, STATX_BASIC_STATS);
}
static inline int vfs_fstatat(int dfd, const char __user *filename,
                              struct kstat *stat, int flags)
{
        return vfs_statx(dfd, filename, flags | AT_NO_AUTOMOUNT,
                         stat, STATX_BASIC_STATS);
}
static inline int vfs_fstat(int fd, struct kstat *stat)
{
        return vfs_statx_fd(fd, stat, STATX_BASIC_STATS, 0);
}


extern const char *vfs_get_link(struct dentry *, struct delayed_call *);
extern int vfs_readlink(struct dentry *, char __user *, int);

extern int __generic_block_fiemap(struct inode *inode,
                                  struct fiemap_extent_info *fieinfo,
                                  loff_t start, loff_t len,
                                  get_block_t *get_block);
extern int generic_block_fiemap(struct inode *inode,
                                struct fiemap_extent_info *fieinfo, u64 start,
                                u64 len, get_block_t *get_block);

extern struct file_system_type *get_filesystem(struct file_system_type *fs);
extern void put_filesystem(struct file_system_type *fs);
extern struct file_system_type *get_fs_type(const char *name);
extern struct super_block *get_super(struct block_device *);
extern struct super_block *get_super_thawed(struct block_device *);
extern struct super_block *get_super_exclusive_thawed(struct block_device *bdev);
extern struct super_block *get_active_super(struct block_device *bdev);
extern void drop_super(struct super_block *sb);
extern void drop_super_exclusive(struct super_block *sb);
extern void iterate_supers(void (*)(struct super_block *, void *), void *);
extern void iterate_supers_type(struct file_system_type *,
                                void (*)(struct super_block *, void *), void *);

extern int dcache_dir_open(struct inode *, struct file *);
extern int dcache_dir_close(struct inode *, struct file *);
extern loff_t dcache_dir_lseek(struct file *, loff_t, int);
extern int dcache_readdir(struct file *, struct dir_context *);
extern int simple_setattr(struct dentry *, struct iattr *);
extern int simple_getattr(const struct path *, struct kstat *, u32, unsigned int);
extern int simple_statfs(struct dentry *, struct kstatfs *);
extern int simple_open(struct inode *inode, struct file *file);
extern int simple_link(struct dentry *, struct inode *, struct dentry *);
extern int simple_unlink(struct inode *, struct dentry *);
extern int simple_rmdir(struct inode *, struct dentry *);
extern int simple_rename(struct inode *, struct dentry *,
                         struct inode *, struct dentry *, unsigned int);
extern int noop_fsync(struct file *, loff_t, loff_t, int);
extern int noop_set_page_dirty(struct page *page);
extern void noop_invalidatepage(struct page *page, unsigned int offset,
                unsigned int length);
extern ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
extern int simple_empty(struct dentry *);
extern int simple_readpage(struct file *file, struct page *page);
extern int simple_write_begin(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata);
extern int simple_write_end(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata);
extern int always_delete_dentry(const struct dentry *);
extern struct inode *alloc_anon_inode(struct super_block *);
extern int simple_nosetlease(struct file *, long, struct file_lock **, void **);
extern const struct dentry_operations simple_dentry_operations;

extern struct dentry *simple_lookup(struct inode *, struct dentry *, unsigned int flags);
extern ssize_t generic_read_dir(struct file *, char __user *, size_t, loff_t *);
extern const struct file_operations simple_dir_operations;
extern const struct inode_operations simple_dir_inode_operations;
extern void make_empty_dir_inode(struct inode *inode);
extern bool is_empty_dir_inode(struct inode *inode);
struct tree_descr { const char *name; const struct file_operations *ops; int mode; };
struct dentry *d_alloc_name(struct dentry *, const char *);
extern int simple_fill_super(struct super_block *, unsigned long,
                             const struct tree_descr *);
extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
extern void simple_release_fs(struct vfsmount **mount, int *count);

extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
                        loff_t *ppos, const void *from, size_t available);
extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
                const void __user *from, size_t count);

extern int __generic_file_fsync(struct file *, loff_t, loff_t, int);
extern int generic_file_fsync(struct file *, loff_t, loff_t, int);

extern int generic_check_addressable(unsigned, u64);

#ifdef CONFIG_MIGRATION
extern int buffer_migrate_page(struct address_space *,
                                struct page *, struct page *,
                                enum migrate_mode);
#else
#define buffer_migrate_page NULL
#endif

extern int setattr_prepare(struct dentry *, struct iattr *);
extern int inode_newsize_ok(const struct inode *, loff_t offset);
extern void setattr_copy(struct inode *inode, const struct iattr *attr);

extern int file_update_time(struct file *file);

static inline bool io_is_direct(struct file *filp)
{
        return (filp->f_flags & O_DIRECT) || IS_DAX(filp->f_mapping->host);
}

static inline bool vma_is_dax(struct vm_area_struct *vma)
{
        return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
}

static inline bool vma_is_fsdax(struct vm_area_struct *vma)
{
        struct inode *inode;

        if (!vma->vm_file)
                return false;
        if (!vma_is_dax(vma))
                return false;
        inode = file_inode(vma->vm_file);
        if (S_ISCHR(inode->i_mode))
                return false; /* device-dax */
        return true;
}

static inline int iocb_flags(struct file *file)
{
        int res = 0;
        if (file->f_flags & O_APPEND)
                res |= IOCB_APPEND;
        if (io_is_direct(file))
                res |= IOCB_DIRECT;
        if ((file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host))
                res |= IOCB_DSYNC;
        if (file->f_flags & __O_SYNC)
                res |= IOCB_SYNC;
        return res;
}

static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
{
        if (unlikely(flags & ~RWF_SUPPORTED))
                return -EOPNOTSUPP;

        if (flags & RWF_NOWAIT) {
                if (!(ki->ki_filp->f_mode & FMODE_NOWAIT))
                        return -EOPNOTSUPP;
                ki->ki_flags |= IOCB_NOWAIT;
        }
        if (flags & RWF_HIPRI)
                ki->ki_flags |= IOCB_HIPRI;
        if (flags & RWF_DSYNC)
                ki->ki_flags |= IOCB_DSYNC;
        if (flags & RWF_SYNC)
                ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
        if (flags & RWF_APPEND)
                ki->ki_flags |= IOCB_APPEND;
        return 0;
}

static inline ino_t parent_ino(struct dentry *dentry)
{
        ino_t res;

        /*
         * Don't strictly need d_lock here? If the parent ino could change
         * then surely we'd have a deeper race in the caller?
         */
        spin_lock(&dentry->d_lock);
        res = dentry->d_parent->d_inode->i_ino;
        spin_unlock(&dentry->d_lock);
        return res;
}

/* Transaction based IO helpers */

/*
 * An argresp is stored in an allocated page and holds the
 * size of the argument or response, along with its content
 */
struct simple_transaction_argresp {
        ssize_t size;
        char data[0];
};

#define SIMPLE_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct simple_transaction_argresp))

char *simple_transaction_get(struct file *file, const char __user *buf,
                                size_t size);
ssize_t simple_transaction_read(struct file *file, char __user *buf,
                                size_t size, loff_t *pos);
int simple_transaction_release(struct inode *inode, struct file *file);

void simple_transaction_set(struct file *file, size_t n);

/*
 * simple attribute files
 *
 * These attributes behave similar to those in sysfs:
 *
 * Writing to an attribute immediately sets a value, an open file can be
 * written to multiple times.
 *
 * Reading from an attribute creates a buffer from the value that might get
 * read with multiple read calls. When the attribute has been read
 * completely, no further read calls are possible until the file is opened
 * again.
 *
 * All attributes contain a text representation of a numeric value
 * that are accessed with the get() and set() functions.
 */
#define DEFINE_SIMPLE_ATTRIBUTE(__fops, __get, __set, __fmt)            \
static int __fops ## _open(struct inode *inode, struct file *file)      \
{                                                                       \
        __simple_attr_check_format(__fmt, 0ull);                        \
        return simple_attr_open(inode, file, __get, __set, __fmt);      \
}                                                                       \
static const struct file_operations __fops = {                          \
        .owner   = THIS_MODULE,                                         \
        .open    = __fops ## _open,                                     \
        .release = simple_attr_release,                                 \
        .read    = simple_attr_read,                                    \
        .write   = simple_attr_write,                                   \
        .llseek  = generic_file_llseek,                                 \
}

static inline __printf(1, 2)
void __simple_attr_check_format(const char *fmt, ...)
{
        /* don't do anything, just let the compiler check the arguments; */
}

int simple_attr_open(struct inode *inode, struct file *file,
                     int (*get)(void *, u64 *), int (*set)(void *, u64),
                     const char *fmt);
int simple_attr_release(struct inode *inode, struct file *file);
ssize_t simple_attr_read(struct file *file, char __user *buf,
                         size_t len, loff_t *ppos);
ssize_t simple_attr_write(struct file *file, const char __user *buf,
                          size_t len, loff_t *ppos);

struct ctl_table;
int proc_nr_files(struct ctl_table *table, int write,
                  void __user *buffer, size_t *lenp, loff_t *ppos);
int proc_nr_dentry(struct ctl_table *table, int write,
                  void __user *buffer, size_t *lenp, loff_t *ppos);
int proc_nr_inodes(struct ctl_table *table, int write,
                   void __user *buffer, size_t *lenp, loff_t *ppos);
int __init get_filesystem_list(char *buf);

#define __FMODE_EXEC            ((__force int) FMODE_EXEC)
#define __FMODE_NONOTIFY        ((__force int) FMODE_NONOTIFY)

#define ACC_MODE(x) ("\004\002\006\006"[(x)&O_ACCMODE])
#define OPEN_FMODE(flag) ((__force fmode_t)(((flag + 1) & O_ACCMODE) | \
                                            (flag & __FMODE_NONOTIFY)))

static inline bool is_sxid(umode_t mode)
{
        return (mode & S_ISUID) || ((mode & S_ISGID) && (mode & S_IXGRP));
}

static inline int check_sticky(struct inode *dir, struct inode *inode)
{
        if (!(dir->i_mode & S_ISVTX))
                return 0;

        return __check_sticky(dir, inode);
}

static inline void inode_has_no_xattr(struct inode *inode)
{
        if (!is_sxid(inode->i_mode) && (inode->i_sb->s_flags & SB_NOSEC))
                inode->i_flags |= S_NOSEC;
}

static inline bool is_root_inode(struct inode *inode)
{
        return inode == inode->i_sb->s_root->d_inode;
}

static inline bool dir_emit(struct dir_context *ctx,
                            const char *name, int namelen,
                            u64 ino, unsigned type)
{
        return ctx->actor(ctx, name, namelen, ctx->pos, ino, type) == 0;
}
static inline bool dir_emit_dot(struct file *file, struct dir_context *ctx)
{
        return ctx->actor(ctx, ".", 1, ctx->pos,
                          file->f_path.dentry->d_inode->i_ino, DT_DIR) == 0;
}
static inline bool dir_emit_dotdot(struct file *file, struct dir_context *ctx)
{
        return ctx->actor(ctx, "..", 2, ctx->pos,
                          parent_ino(file->f_path.dentry), DT_DIR) == 0;
}
static inline bool dir_emit_dots(struct file *file, struct dir_context *ctx)
{
        if (ctx->pos == 0) {
                if (!dir_emit_dot(file, ctx))
                        return false;
                ctx->pos = 1;
        }
        if (ctx->pos == 1) {
                if (!dir_emit_dotdot(file, ctx))
                        return false;
                ctx->pos = 2;
        }
        return true;
}
static inline bool dir_relax(struct inode *inode)
{
        inode_unlock(inode);
        inode_lock(inode);
        return !IS_DEADDIR(inode);
}

static inline bool dir_relax_shared(struct inode *inode)
{
        inode_unlock_shared(inode);
        inode_lock_shared(inode);
        return !IS_DEADDIR(inode);
}

extern bool path_noexec(const struct path *path);
extern void inode_nohighmem(struct inode *inode);

/* mm/fadvise.c */
extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,
                       int advice);

#endif /* _LINUX_FS_H */