GNU Linux-libre 4.9.332-gnu1

[releases.git] / drivers / staging / lustre / lustre / include / lustre_dlm.h

/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2010, 2015, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 */

/** \defgroup LDLM Lustre Distributed Lock Manager
 *
 * Lustre DLM is based on VAX DLM.
 * Its two main roles are:
 *   - To provide locking assuring consistency of data on all Lustre nodes.
 *   - To allow clients to cache state protected by a lock by holding the
 *     lock until a conflicting lock is requested or it is expired by the LRU.
 *
 * @{
 */

#ifndef _LUSTRE_DLM_H__
#define _LUSTRE_DLM_H__

#include "lustre_lib.h"
#include "lustre_net.h"
#include "lustre_import.h"
#include "lustre_handles.h"
#include "interval_tree.h"      /* for interval_node{}, ldlm_extent */
#include "lu_ref.h"

#include "lustre_dlm_flags.h"

struct obd_ops;
struct obd_device;

#define OBD_LDLM_DEVICENAME  "ldlm"

#define LDLM_DEFAULT_LRU_SIZE (100 * num_online_cpus())
#define LDLM_DEFAULT_MAX_ALIVE (cfs_time_seconds(36000))
#define LDLM_DEFAULT_PARALLEL_AST_LIMIT 1024

/**
 * LDLM non-error return states
 */
enum ldlm_error {
        ELDLM_OK = 0,
        ELDLM_LOCK_MATCHED = 1,

        ELDLM_LOCK_CHANGED = 300,
        ELDLM_LOCK_ABORTED = 301,
        ELDLM_LOCK_REPLACED = 302,
        ELDLM_NO_LOCK_DATA = 303,
        ELDLM_LOCK_WOULDBLOCK = 304,

        ELDLM_NAMESPACE_EXISTS = 400,
        ELDLM_BAD_NAMESPACE    = 401
};

/**
 * LDLM namespace type.
 * The "client" type is actually an indication that this is a narrow local view
 * into complete namespace on the server. Such namespaces cannot make any
 * decisions about lack of conflicts or do any autonomous lock granting without
 * first speaking to a server.
 */
typedef enum {
        LDLM_NAMESPACE_SERVER = 1 << 0,
        LDLM_NAMESPACE_CLIENT = 1 << 1
} ldlm_side_t;

/**
 * The blocking callback is overloaded to perform two functions.  These flags
 * indicate which operation should be performed.
 */
#define LDLM_CB_BLOCKING    1
#define LDLM_CB_CANCELING   2

/**
 * \name Lock Compatibility Matrix.
 *
 * A lock has both a type (extent, flock, inode bits, or plain) and a mode.
 * Lock types are described in their respective implementation files:
 * ldlm_{extent,flock,inodebits,plain}.c.
 *
 * There are six lock modes along with a compatibility matrix to indicate if
 * two locks are compatible.
 *
 * - EX: Exclusive mode. Before a new file is created, MDS requests EX lock
 *   on the parent.
 * - PW: Protective Write (normal write) mode. When a client requests a write
 *   lock from an OST, a lock with PW mode will be issued.
 * - PR: Protective Read (normal read) mode. When a client requests a read from
 *   an OST, a lock with PR mode will be issued. Also, if the client opens a
 *   file for execution, it is granted a lock with PR mode.
 * - CW: Concurrent Write mode. The type of lock that the MDS grants if a client
 *   requests a write lock during a file open operation.
 * - CR Concurrent Read mode. When a client performs a path lookup, MDS grants
 *   an inodebit lock with the CR mode on the intermediate path component.
 * - NL Null mode.
 *
 * <PRE>
 *       NL  CR  CW  PR  PW  EX
 *  NL    1   1   1   1   1   1
 *  CR    1   1   1   1   1   0
 *  CW    1   1   1   0   0   0
 *  PR    1   1   0   1   0   0
 *  PW    1   1   0   0   0   0
 *  EX    1   0   0   0   0   0
 * </PRE>
 */
/** @{ */
#define LCK_COMPAT_EX  LCK_NL
#define LCK_COMPAT_PW  (LCK_COMPAT_EX | LCK_CR)
#define LCK_COMPAT_PR  (LCK_COMPAT_PW | LCK_PR)
#define LCK_COMPAT_CW  (LCK_COMPAT_PW | LCK_CW)
#define LCK_COMPAT_CR  (LCK_COMPAT_CW | LCK_PR | LCK_PW)
#define LCK_COMPAT_NL  (LCK_COMPAT_CR | LCK_EX | LCK_GROUP)
#define LCK_COMPAT_GROUP  (LCK_GROUP | LCK_NL)
#define LCK_COMPAT_COS (LCK_COS)
/** @} Lock Compatibility Matrix */

extern enum ldlm_mode lck_compat_array[];

static inline void lockmode_verify(enum ldlm_mode mode)
{
        LASSERT(mode > LCK_MINMODE && mode < LCK_MAXMODE);
}

static inline int lockmode_compat(enum ldlm_mode exist_mode,
                                  enum ldlm_mode new_mode)
{
        return (lck_compat_array[exist_mode] & new_mode);
}

/*
 *
 * cluster name spaces
 *
 */

#define DLM_OST_NAMESPACE 1
#define DLM_MDS_NAMESPACE 2

/* XXX
   - do we just separate this by security domains and use a prefix for
     multiple namespaces in the same domain?
   -
*/

/**
 * Locking rules for LDLM:
 *
 * lr_lock
 *
 * lr_lock
 *     waiting_locks_spinlock
 *
 * lr_lock
 *     led_lock
 *
 * lr_lock
 *     ns_lock
 *
 * lr_lvb_mutex
 *     lr_lock
 *
 */

struct ldlm_pool;
struct ldlm_lock;
struct ldlm_resource;
struct ldlm_namespace;

/**
 * Operations on LDLM pools.
 * LDLM pool is a pool of locks in the namespace without any implicitly
 * specified limits.
 * Locks in the pool are organized in LRU.
 * Local memory pressure or server instructions (e.g. mempressure on server)
 * can trigger freeing of locks from the pool
 */
struct ldlm_pool_ops {
        /** Recalculate pool \a pl usage */
        int (*po_recalc)(struct ldlm_pool *pl);
        /** Cancel at least \a nr locks from pool \a pl */
        int (*po_shrink)(struct ldlm_pool *pl, int nr,
                         gfp_t gfp_mask);
};

/** One second for pools thread check interval. Each pool has own period. */
#define LDLM_POOLS_THREAD_PERIOD (1)

/** ~6% margin for modest pools. See ldlm_pool.c for details. */
#define LDLM_POOLS_MODEST_MARGIN_SHIFT (4)

/** Default recalc period for server side pools in sec. */
#define LDLM_POOL_SRV_DEF_RECALC_PERIOD (1)

/** Default recalc period for client side pools in sec. */
#define LDLM_POOL_CLI_DEF_RECALC_PERIOD (10)

/**
 * LDLM pool structure to track granted locks.
 * For purposes of determining when to release locks on e.g. memory pressure.
 * This feature is commonly referred to as lru_resize.
 */
struct ldlm_pool {
        /** Pool debugfs directory. */
        struct dentry           *pl_debugfs_entry;
        /** Pool name, must be long enough to hold compound proc entry name. */
        char                    pl_name[100];
        /** Lock for protecting SLV/CLV updates. */
        spinlock_t              pl_lock;
        /** Number of allowed locks in in pool, both, client and server side. */
        atomic_t                pl_limit;
        /** Number of granted locks in */
        atomic_t                pl_granted;
        /** Grant rate per T. */
        atomic_t                pl_grant_rate;
        /** Cancel rate per T. */
        atomic_t                pl_cancel_rate;
        /** Server lock volume (SLV). Protected by pl_lock. */
        __u64                   pl_server_lock_volume;
        /** Current biggest client lock volume. Protected by pl_lock. */
        __u64                   pl_client_lock_volume;
        /** Lock volume factor. SLV on client is calculated as following:
         *  server_slv * lock_volume_factor.
         */
        atomic_t                pl_lock_volume_factor;
        /** Time when last SLV from server was obtained. */
        time64_t                pl_recalc_time;
        /** Recalculation period for pool. */
        time64_t                pl_recalc_period;
        /** Recalculation and shrink operations. */
        const struct ldlm_pool_ops      *pl_ops;
        /** Number of planned locks for next period. */
        int                     pl_grant_plan;
        /** Pool statistics. */
        struct lprocfs_stats    *pl_stats;

        /* sysfs object */
        struct kobject           pl_kobj;
        struct completion        pl_kobj_unregister;
};

typedef int (*ldlm_cancel_cbt)(struct ldlm_lock *lock);

/**
 * LVB operations.
 * LVB is Lock Value Block. This is a special opaque (to LDLM) value that could
 * be associated with an LDLM lock and transferred from client to server and
 * back.
 *
 * Currently LVBs are used by:
 *  - OSC-OST code to maintain current object size/times
 *  - layout lock code to return the layout when the layout lock is granted
 */
struct ldlm_valblock_ops {
        int (*lvbo_init)(struct ldlm_resource *res);
        int (*lvbo_update)(struct ldlm_resource *res,
                           struct ptlrpc_request *r,
                           int increase);
        int (*lvbo_free)(struct ldlm_resource *res);
        /* Return size of lvb data appropriate RPC size can be reserved */
        int (*lvbo_size)(struct ldlm_lock *lock);
        /* Called to fill in lvb data to RPC buffer @buf */
        int (*lvbo_fill)(struct ldlm_lock *lock, void *buf, int buflen);
};

/**
 * LDLM pools related, type of lock pool in the namespace.
 * Greedy means release cached locks aggressively
 */
enum ldlm_appetite {
        LDLM_NAMESPACE_GREEDY = 1 << 0,
        LDLM_NAMESPACE_MODEST = 1 << 1
};

struct ldlm_ns_bucket {
        /** back pointer to namespace */
        struct ldlm_namespace      *nsb_namespace;
        /**
         * Estimated lock callback time.  Used by adaptive timeout code to
         * avoid spurious client evictions due to unresponsiveness when in
         * fact the network or overall system load is at fault
         */
        struct adaptive_timeout     nsb_at_estimate;
};

enum {
        /** LDLM namespace lock stats */
        LDLM_NSS_LOCKS    = 0,
        LDLM_NSS_LAST
};

enum ldlm_ns_type {
        /** invalid type */
        LDLM_NS_TYPE_UNKNOWN    = 0,
        /** mdc namespace */
        LDLM_NS_TYPE_MDC,
        /** mds namespace */
        LDLM_NS_TYPE_MDT,
        /** osc namespace */
        LDLM_NS_TYPE_OSC,
        /** ost namespace */
        LDLM_NS_TYPE_OST,
        /** mgc namespace */
        LDLM_NS_TYPE_MGC,
        /** mgs namespace */
        LDLM_NS_TYPE_MGT,
};

/**
 * LDLM Namespace.
 *
 * Namespace serves to contain locks related to a particular service.
 * There are two kinds of namespaces:
 * - Server namespace has knowledge of all locks and is therefore authoritative
 *   to make decisions like what locks could be granted and what conflicts
 *   exist during new lock enqueue.
 * - Client namespace only has limited knowledge about locks in the namespace,
 *   only seeing locks held by the client.
 *
 * Every Lustre service has one server namespace present on the server serving
 * that service. Every client connected to the service has a client namespace
 * for it.
 * Every lock obtained by client in that namespace is actually represented by
 * two in-memory locks. One on the server and one on the client. The locks are
 * linked by a special cookie by which one node can tell to the other which lock
 * it actually means during communications. Such locks are called remote locks.
 * The locks held by server only without any reference to a client are called
 * local locks.
 */
struct ldlm_namespace {
        /** Backward link to OBD, required for LDLM pool to store new SLV. */
        struct obd_device       *ns_obd;

        /** Flag indicating if namespace is on client instead of server */
        ldlm_side_t             ns_client;

        /** Resource hash table for namespace. */
        struct cfs_hash         *ns_rs_hash;

        /** serialize */
        spinlock_t              ns_lock;

        /** big refcount (by bucket) */
        atomic_t                ns_bref;

        /**
         * Namespace connect flags supported by server (may be changed via
         * sysfs, LRU resize may be disabled/enabled).
         */
        __u64                   ns_connect_flags;

        /** Client side original connect flags supported by server. */
        __u64                   ns_orig_connect_flags;

        /* namespace debugfs dir entry */
        struct dentry           *ns_debugfs_entry;

        /**
         * Position in global namespace list linking all namespaces on
         * the node.
         */
        struct list_head                ns_list_chain;

        /**
         * List of unused locks for this namespace. This list is also called
         * LRU lock list.
         * Unused locks are locks with zero reader/writer reference counts.
         * This list is only used on clients for lock caching purposes.
         * When we want to release some locks voluntarily or if server wants
         * us to release some locks due to e.g. memory pressure, we take locks
         * to release from the head of this list.
         * Locks are linked via l_lru field in \see struct ldlm_lock.
         */
        struct list_head                ns_unused_list;
        /** Number of locks in the LRU list above */
        int                     ns_nr_unused;

        /**
         * Maximum number of locks permitted in the LRU. If 0, means locks
         * are managed by pools and there is no preset limit, rather it is all
         * controlled by available memory on this client and on server.
         */
        unsigned int            ns_max_unused;
        /** Maximum allowed age (last used time) for locks in the LRU */
        unsigned int            ns_max_age;

        /**
         * Used to rate-limit ldlm_namespace_dump calls.
         * \see ldlm_namespace_dump. Increased by 10 seconds every time
         * it is called.
         */
        unsigned long           ns_next_dump;

        /**
         * LVB operations for this namespace.
         * \see struct ldlm_valblock_ops
         */
        struct ldlm_valblock_ops *ns_lvbo;

        /**
         * Used by filter code to store pointer to OBD of the service.
         * Should be dropped in favor of \a ns_obd
         */
        void                    *ns_lvbp;

        /**
         * Wait queue used by __ldlm_namespace_free. Gets woken up every time
         * a resource is removed.
         */
        wait_queue_head_t               ns_waitq;
        /** LDLM pool structure for this namespace */
        struct ldlm_pool        ns_pool;
        /** Definition of how eagerly unused locks will be released from LRU */
        enum ldlm_appetite      ns_appetite;

        /** Limit of parallel AST RPC count. */
        unsigned                ns_max_parallel_ast;

        /**
         * Callback to check if a lock is good to be canceled by ELC or
         * during recovery.
         */
        ldlm_cancel_cbt         ns_cancel;

        /** LDLM lock stats */
        struct lprocfs_stats    *ns_stats;

        /**
         * Flag to indicate namespace is being freed. Used to determine if
         * recalculation of LDLM pool statistics should be skipped.
         */
        unsigned                ns_stopping:1;

        struct kobject          ns_kobj; /* sysfs object */
        struct completion       ns_kobj_unregister;
};

/**
 * Returns 1 if namespace \a ns supports early lock cancel (ELC).
 */
static inline int ns_connect_cancelset(struct ldlm_namespace *ns)
{
        return !!(ns->ns_connect_flags & OBD_CONNECT_CANCELSET);
}

/**
 * Returns 1 if this namespace supports lru_resize.
 */
static inline int ns_connect_lru_resize(struct ldlm_namespace *ns)
{
        return !!(ns->ns_connect_flags & OBD_CONNECT_LRU_RESIZE);
}

static inline void ns_register_cancel(struct ldlm_namespace *ns,
                                      ldlm_cancel_cbt arg)
{
        ns->ns_cancel = arg;
}

struct ldlm_lock;

/** Type for blocking callback function of a lock. */
typedef int (*ldlm_blocking_callback)(struct ldlm_lock *lock,
                                      struct ldlm_lock_desc *new, void *data,
                                      int flag);
/** Type for completion callback function of a lock. */
typedef int (*ldlm_completion_callback)(struct ldlm_lock *lock, __u64 flags,
                                        void *data);
/** Type for glimpse callback function of a lock. */
typedef int (*ldlm_glimpse_callback)(struct ldlm_lock *lock, void *data);

/** Work list for sending GL ASTs to multiple locks. */
struct ldlm_glimpse_work {
        struct ldlm_lock        *gl_lock; /* lock to glimpse */
        struct list_head                 gl_list; /* linkage to other gl work structs */
        __u32                    gl_flags;/* see LDLM_GL_WORK_* below */
        union ldlm_gl_desc      *gl_desc; /* glimpse descriptor to be packed in
                                           * glimpse callback request
                                           */
};

/** The ldlm_glimpse_work is allocated on the stack and should not be freed. */
#define LDLM_GL_WORK_NOFREE 0x1

/** Interval node data for each LDLM_EXTENT lock. */
struct ldlm_interval {
        struct interval_node    li_node;  /* node for tree management */
        struct list_head        li_group; /* the locks which have the same
                                           * policy - group of the policy
                                           */
};

#define to_ldlm_interval(n) container_of(n, struct ldlm_interval, li_node)

/**
 * Interval tree for extent locks.
 * The interval tree must be accessed under the resource lock.
 * Interval trees are used for granted extent locks to speed up conflicts
 * lookup. See ldlm/interval_tree.c for more details.
 */
struct ldlm_interval_tree {
        /** Tree size. */
        int                     lit_size;
        enum ldlm_mode          lit_mode;  /* lock mode */
        struct interval_node    *lit_root; /* actual ldlm_interval */
};

/** Whether to track references to exports by LDLM locks. */
#define LUSTRE_TRACKS_LOCK_EXP_REFS (0)

/** Cancel flags. */
enum ldlm_cancel_flags {
        LCF_ASYNC      = 0x1, /* Cancel locks asynchronously. */
        LCF_LOCAL      = 0x2, /* Cancel locks locally, not notifing server */
        LCF_BL_AST     = 0x4, /* Cancel locks marked as LDLM_FL_BL_AST
                               * in the same RPC
                               */
};

struct ldlm_flock {
        __u64 start;
        __u64 end;
        __u64 owner;
        __u64 blocking_owner;
        struct obd_export *blocking_export;
        /* Protected by the hash lock */
        __u32 blocking_refs;
        __u32 pid;
};

typedef union {
        struct ldlm_extent l_extent;
        struct ldlm_flock l_flock;
        struct ldlm_inodebits l_inodebits;
} ldlm_policy_data_t;

void ldlm_convert_policy_to_local(struct obd_export *exp, enum ldlm_type type,
                                  const ldlm_wire_policy_data_t *wpolicy,
                                  ldlm_policy_data_t *lpolicy);

enum lvb_type {
        LVB_T_NONE      = 0,
        LVB_T_OST       = 1,
        LVB_T_LQUOTA    = 2,
        LVB_T_LAYOUT    = 3,
};

/**
 * LDLM_GID_ANY is used to match any group id in ldlm_lock_match().
 */
#define LDLM_GID_ANY    ((__u64)-1)

/**
 * LDLM lock structure
 *
 * Represents a single LDLM lock and its state in memory. Each lock is
 * associated with a single ldlm_resource, the object which is being
 * locked. There may be multiple ldlm_locks on a single resource,
 * depending on the lock type and whether the locks are conflicting or
 * not.
 */
struct ldlm_lock {
        /**
         * Local lock handle.
         * When remote side wants to tell us about a lock, they address
         * it by this opaque handle.  The handle does not hold a
         * reference on the ldlm_lock, so it can be safely passed to
         * other threads or nodes. When the lock needs to be accessed
         * from the handle, it is looked up again in the lock table, and
         * may no longer exist.
         *
         * Must be first in the structure.
         */
        struct portals_handle   l_handle;
        /**
         * Lock reference count.
         * This is how many users have pointers to actual structure, so that
         * we do not accidentally free lock structure that is in use.
         */
        atomic_t                l_refc;
        /**
         * Internal spinlock protects l_resource.  We should hold this lock
         * first before taking res_lock.
         */
        spinlock_t              l_lock;
        /**
         * Pointer to actual resource this lock is in.
         * ldlm_lock_change_resource() can change this.
         */
        struct ldlm_resource    *l_resource;
        /**
         * List item for client side LRU list.
         * Protected by ns_lock in struct ldlm_namespace.
         */
        struct list_head                l_lru;
        /**
         * Linkage to resource's lock queues according to current lock state.
         * (could be granted, waiting or converting)
         * Protected by lr_lock in struct ldlm_resource.
         */
        struct list_head                l_res_link;
        /**
         * Tree node for ldlm_extent.
         */
        struct ldlm_interval    *l_tree_node;
        /**
         * Per export hash of locks.
         * Protected by per-bucket exp->exp_lock_hash locks.
         */
        struct hlist_node       l_exp_hash;
        /**
         * Per export hash of flock locks.
         * Protected by per-bucket exp->exp_flock_hash locks.
         */
        struct hlist_node       l_exp_flock_hash;
        /**
         * Requested mode.
         * Protected by lr_lock.
         */
        enum ldlm_mode          l_req_mode;
        /**
         * Granted mode, also protected by lr_lock.
         */
        enum ldlm_mode          l_granted_mode;
        /** Lock completion handler pointer. Called when lock is granted. */
        ldlm_completion_callback l_completion_ast;
        /**
         * Lock blocking AST handler pointer.
         * It plays two roles:
         * - as a notification of an attempt to queue a conflicting lock (once)
         * - as a notification when the lock is being cancelled.
         *
         * As such it's typically called twice: once for the initial conflict
         * and then once more when the last user went away and the lock is
         * cancelled (could happen recursively).
         */
        ldlm_blocking_callback  l_blocking_ast;
        /**
         * Lock glimpse handler.
         * Glimpse handler is used to obtain LVB updates from a client by
         * server
         */
        ldlm_glimpse_callback   l_glimpse_ast;

        /**
         * Lock export.
         * This is a pointer to actual client export for locks that were granted
         * to clients. Used server-side.
         */
        struct obd_export       *l_export;
        /**
         * Lock connection export.
         * Pointer to server export on a client.
         */
        struct obd_export       *l_conn_export;

        /**
         * Remote lock handle.
         * If the lock is remote, this is the handle of the other side lock
         * (l_handle)
         */
        struct lustre_handle    l_remote_handle;

        /**
         * Representation of private data specific for a lock type.
         * Examples are: extent range for extent lock or bitmask for ibits locks
         */
        ldlm_policy_data_t      l_policy_data;

        /**
         * Lock state flags. Protected by lr_lock.
         * \see lustre_dlm_flags.h where the bits are defined.
         */
        __u64                   l_flags;

        /**
         * Lock r/w usage counters.
         * Protected by lr_lock.
         */
        __u32                   l_readers;
        __u32                   l_writers;
        /**
         * If the lock is granted, a process sleeps on this waitq to learn when
         * it's no longer in use.  If the lock is not granted, a process sleeps
         * on this waitq to learn when it becomes granted.
         */
        wait_queue_head_t               l_waitq;

        /**
         * Seconds. It will be updated if there is any activity related to
         * the lock, e.g. enqueue the lock or send blocking AST.
         */
        time64_t                l_last_activity;

        /**
         * Time last used by e.g. being matched by lock match.
         * Jiffies. Should be converted to time if needed.
         */
        unsigned long           l_last_used;

        /** Originally requested extent for the extent lock. */
        struct ldlm_extent      l_req_extent;

        /*
         * Client-side-only members.
         */

        enum lvb_type         l_lvb_type;

        /**
         * Temporary storage for a LVB received during an enqueue operation.
         */
        __u32                   l_lvb_len;
        void                    *l_lvb_data;

        /** Private storage for lock user. Opaque to LDLM. */
        void                    *l_ast_data;

        /*
         * Server-side-only members.
         */

        /**
         * Connection cookie for the client originating the operation.
         * Used by Commit on Share (COS) code. Currently only used for
         * inodebits locks on MDS.
         */
        __u64                   l_client_cookie;

        /**
         * List item for locks waiting for cancellation from clients.
         * The lists this could be linked into are:
         * waiting_locks_list (protected by waiting_locks_spinlock),
         * then if the lock timed out, it is moved to
         * expired_lock_thread.elt_expired_locks for further processing.
         * Protected by elt_lock.
         */
        struct list_head                l_pending_chain;

        /**
         * Set when lock is sent a blocking AST. Time in seconds when timeout
         * is reached and client holding this lock could be evicted.
         * This timeout could be further extended by e.g. certain IO activity
         * under this lock.
         * \see ost_rw_prolong_locks
         */
        unsigned long           l_callback_timeout;

        /** Local PID of process which created this lock. */
        __u32                   l_pid;

        /**
         * Number of times blocking AST was sent for this lock.
         * This is for debugging. Valid values are 0 and 1, if there is an
         * attempt to send blocking AST more than once, an assertion would be
         * hit. \see ldlm_work_bl_ast_lock
         */
        int                     l_bl_ast_run;
        /** List item ldlm_add_ast_work_item() for case of blocking ASTs. */
        struct list_head                l_bl_ast;
        /** List item ldlm_add_ast_work_item() for case of completion ASTs. */
        struct list_head                l_cp_ast;
        /** For ldlm_add_ast_work_item() for "revoke" AST used in COS. */
        struct list_head                l_rk_ast;

        /**
         * Pointer to a conflicting lock that caused blocking AST to be sent
         * for this lock
         */
        struct ldlm_lock        *l_blocking_lock;

        /**
         * Protected by lr_lock, linkages to "skip lists".
         * For more explanations of skip lists see ldlm/ldlm_inodebits.c
         */
        struct list_head                l_sl_mode;
        struct list_head                l_sl_policy;

        /** Reference tracking structure to debug leaked locks. */
        struct lu_ref           l_reference;
#if LUSTRE_TRACKS_LOCK_EXP_REFS
        /* Debugging stuff for bug 20498, for tracking export references. */
        /** number of export references taken */
        int                     l_exp_refs_nr;
        /** link all locks referencing one export */
        struct list_head                l_exp_refs_link;
        /** referenced export object */
        struct obd_export       *l_exp_refs_target;
#endif
        /**
         * export blocking dlm lock list, protected by
         * l_export->exp_bl_list_lock.
         * Lock order of waiting_lists_spinlock, exp_bl_list_lock and res lock
         * is: res lock -> exp_bl_list_lock -> wanting_lists_spinlock.
         */
        struct list_head                l_exp_list;
};

/**
 * LDLM resource description.
 * Basically, resource is a representation for a single object.
 * Object has a name which is currently 4 64-bit integers. LDLM user is
 * responsible for creation of a mapping between objects it wants to be
 * protected and resource names.
 *
 * A resource can only hold locks of a single lock type, though there may be
 * multiple ldlm_locks on a single resource, depending on the lock type and
 * whether the locks are conflicting or not.
 */
struct ldlm_resource {
        struct ldlm_ns_bucket   *lr_ns_bucket;

        /**
         * List item for list in namespace hash.
         * protected by ns_lock
         */
        struct hlist_node       lr_hash;

        /** Spinlock to protect locks under this resource. */
        spinlock_t              lr_lock;

        /**
         * protected by lr_lock
         * @{
         */
        /** List of locks in granted state */
        struct list_head                lr_granted;
        /**
         * List of locks that could not be granted due to conflicts and
         * that are waiting for conflicts to go away
         */
        struct list_head                lr_waiting;
        /** @} */

        /** Type of locks this resource can hold. Only one type per resource. */
        enum ldlm_type          lr_type; /* LDLM_{PLAIN,EXTENT,FLOCK,IBITS} */

        /** Resource name */
        struct ldlm_res_id      lr_name;
        /** Reference count for this resource */
        atomic_t                lr_refcount;

        /**
         * Interval trees (only for extent locks) for all modes of this resource
         */
        struct ldlm_interval_tree lr_itree[LCK_MODE_NUM];

        /**
         * Server-side-only lock value block elements.
         * To serialize lvbo_init.
         */
        struct mutex            lr_lvb_mutex;
        int                     lr_lvb_len;

        /** When the resource was considered as contended. */
        unsigned long           lr_contention_time;
        /** List of references to this resource. For debugging. */
        struct lu_ref           lr_reference;

        struct inode            *lr_lvb_inode;
};

static inline bool ldlm_has_layout(struct ldlm_lock *lock)
{
        return lock->l_resource->lr_type == LDLM_IBITS &&
                lock->l_policy_data.l_inodebits.bits & MDS_INODELOCK_LAYOUT;
}

static inline char *
ldlm_ns_name(struct ldlm_namespace *ns)
{
        return ns->ns_rs_hash->hs_name;
}

static inline struct ldlm_namespace *
ldlm_res_to_ns(struct ldlm_resource *res)
{
        return res->lr_ns_bucket->nsb_namespace;
}

static inline struct ldlm_namespace *
ldlm_lock_to_ns(struct ldlm_lock *lock)
{
        return ldlm_res_to_ns(lock->l_resource);
}

static inline char *
ldlm_lock_to_ns_name(struct ldlm_lock *lock)
{
        return ldlm_ns_name(ldlm_lock_to_ns(lock));
}

static inline struct adaptive_timeout *
ldlm_lock_to_ns_at(struct ldlm_lock *lock)
{
        return &lock->l_resource->lr_ns_bucket->nsb_at_estimate;
}

static inline int ldlm_lvbo_init(struct ldlm_resource *res)
{
        struct ldlm_namespace *ns = ldlm_res_to_ns(res);

        if (ns->ns_lvbo && ns->ns_lvbo->lvbo_init)
                return ns->ns_lvbo->lvbo_init(res);

        return 0;
}

static inline int ldlm_lvbo_size(struct ldlm_lock *lock)
{
        struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);

        if (ns->ns_lvbo && ns->ns_lvbo->lvbo_size)
                return ns->ns_lvbo->lvbo_size(lock);

        return 0;
}

static inline int ldlm_lvbo_fill(struct ldlm_lock *lock, void *buf, int len)
{
        struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);

        if (ns->ns_lvbo)
                return ns->ns_lvbo->lvbo_fill(lock, buf, len);

        return 0;
}

struct ldlm_ast_work {
        struct ldlm_lock      *w_lock;
        int                 w_blocking;
        struct ldlm_lock_desc  w_desc;
        struct list_head             w_list;
        int                 w_flags;
        void              *w_data;
        int                 w_datalen;
};

/**
 * Common ldlm_enqueue parameters
 */
struct ldlm_enqueue_info {
        __u32 ei_type;   /** Type of the lock being enqueued. */
        __u32 ei_mode;   /** Mode of the lock being enqueued. */
        void *ei_cb_bl;  /** blocking lock callback */
        void *ei_cb_cp;  /** lock completion callback */
        void *ei_cb_gl;  /** lock glimpse callback */
        void *ei_cbdata; /** Data to be passed into callbacks. */
        unsigned int ei_enq_slave:1; /* whether enqueue slave stripes */
};

extern struct obd_ops ldlm_obd_ops;

extern char *ldlm_lockname[];
char *ldlm_it2str(int it);

/**
 * Just a fancy CDEBUG call with log level preset to LDLM_DEBUG.
 * For the cases where we do not have actual lock to print along
 * with a debugging message that is ldlm-related
 */
#define LDLM_DEBUG_NOLOCK(format, a...)                 \
        CDEBUG(D_DLMTRACE, "### " format "\n", ##a)

/**
 * Support function for lock information printing into debug logs.
 * \see LDLM_DEBUG
 */
#define ldlm_lock_debug(msgdata, mask, cdls, lock, fmt, a...) do {      \
        CFS_CHECK_STACK(msgdata, mask, cdls);                      \
                                                                        \
        if (((mask) & D_CANTMASK) != 0 ||                              \
            ((libcfs_debug & (mask)) != 0 &&                        \
             (libcfs_subsystem_debug & DEBUG_SUBSYSTEM) != 0))    \
                _ldlm_lock_debug(lock, msgdata, fmt, ##a);            \
} while (0)

void _ldlm_lock_debug(struct ldlm_lock *lock,
                      struct libcfs_debug_msg_data *data,
                      const char *fmt, ...)
        __printf(3, 4);

/**
 * Rate-limited version of lock printing function.
 */
#define LDLM_DEBUG_LIMIT(mask, lock, fmt, a...) do {                     \
        static struct cfs_debug_limit_state _ldlm_cdls;                    \
        LIBCFS_DEBUG_MSG_DATA_DECL(msgdata, mask, &_ldlm_cdls);       \
        ldlm_lock_debug(&msgdata, mask, &_ldlm_cdls, lock, "### " fmt, ##a);\
} while (0)

#define LDLM_ERROR(lock, fmt, a...) LDLM_DEBUG_LIMIT(D_ERROR, lock, fmt, ## a)
#define LDLM_WARN(lock, fmt, a...)  LDLM_DEBUG_LIMIT(D_WARNING, lock, fmt, ## a)

/** Non-rate-limited lock printing function for debugging purposes. */
#define LDLM_DEBUG(lock, fmt, a...)   do {                                \
        if (likely(lock)) {                                                 \
                LIBCFS_DEBUG_MSG_DATA_DECL(msgdata, D_DLMTRACE, NULL);      \
                ldlm_lock_debug(&msgdata, D_DLMTRACE, NULL, lock,           \
                                "### " fmt, ##a);                           \
        } else {                                                            \
                LDLM_DEBUG_NOLOCK("no dlm lock: " fmt, ##a);                \
        }                                                                   \
} while (0)

typedef int (*ldlm_processing_policy)(struct ldlm_lock *lock, __u64 *flags,
                                      int first_enq, enum ldlm_error *err,
                                      struct list_head *work_list);

/**
 * Return values for lock iterators.
 * Also used during deciding of lock grants and cancellations.
 */
#define LDLM_ITER_CONTINUE 1 /* keep iterating */
#define LDLM_ITER_STOP     2 /* stop iterating */

typedef int (*ldlm_iterator_t)(struct ldlm_lock *, void *);
typedef int (*ldlm_res_iterator_t)(struct ldlm_resource *, void *);

/** \defgroup ldlm_iterator Lock iterators
 *
 * LDLM provides for a way to iterate through every lock on a resource or
 * namespace or every resource in a namespace.
 * @{
 */
int ldlm_resource_iterate(struct ldlm_namespace *, const struct ldlm_res_id *,
                          ldlm_iterator_t iter, void *data);
/** @} ldlm_iterator */

int ldlm_replay_locks(struct obd_import *imp);

/* ldlm_flock.c */
int ldlm_flock_completion_ast(struct ldlm_lock *lock, __u64 flags, void *data);

/* ldlm_extent.c */
__u64 ldlm_extent_shift_kms(struct ldlm_lock *lock, __u64 old_kms);

struct ldlm_callback_suite {
        ldlm_completion_callback lcs_completion;
        ldlm_blocking_callback   lcs_blocking;
        ldlm_glimpse_callback    lcs_glimpse;
};

/* ldlm_lockd.c */
int ldlm_get_ref(void);
void ldlm_put_ref(void);
struct ldlm_lock *ldlm_request_lock(struct ptlrpc_request *req);

/* ldlm_lock.c */
void ldlm_lock2handle(const struct ldlm_lock *lock,
                      struct lustre_handle *lockh);
struct ldlm_lock *__ldlm_handle2lock(const struct lustre_handle *, __u64 flags);
void ldlm_cancel_callback(struct ldlm_lock *);
int ldlm_lock_remove_from_lru(struct ldlm_lock *);
int ldlm_lock_set_data(const struct lustre_handle *lockh, void *data);

/**
 * Obtain a lock reference by its handle.
 */
static inline struct ldlm_lock *ldlm_handle2lock(const struct lustre_handle *h)
{
        return __ldlm_handle2lock(h, 0);
}

#define LDLM_LOCK_REF_DEL(lock) \
        lu_ref_del(&lock->l_reference, "handle", current)

static inline struct ldlm_lock *
ldlm_handle2lock_long(const struct lustre_handle *h, __u64 flags)
{
        struct ldlm_lock *lock;

        lock = __ldlm_handle2lock(h, flags);
        if (lock)
                LDLM_LOCK_REF_DEL(lock);
        return lock;
}

/**
 * Update Lock Value Block Operations (LVBO) on a resource taking into account
 * data from request \a r
 */
static inline int ldlm_res_lvbo_update(struct ldlm_resource *res,
                                       struct ptlrpc_request *r, int increase)
{
        if (ldlm_res_to_ns(res)->ns_lvbo &&
            ldlm_res_to_ns(res)->ns_lvbo->lvbo_update) {
                return ldlm_res_to_ns(res)->ns_lvbo->lvbo_update(res, r,
                                                                 increase);
        }
        return 0;
}

int ldlm_error2errno(enum ldlm_error error);

#if LUSTRE_TRACKS_LOCK_EXP_REFS
void ldlm_dump_export_locks(struct obd_export *exp);
#endif

/**
 * Release a temporary lock reference obtained by ldlm_handle2lock() or
 * __ldlm_handle2lock().
 */
#define LDLM_LOCK_PUT(lock)                  \
do {                                        \
        LDLM_LOCK_REF_DEL(lock);                \
        /*LDLM_DEBUG((lock), "put");*/    \
        ldlm_lock_put(lock);                \
} while (0)

/**
 * Release a lock reference obtained by some other means (see
 * LDLM_LOCK_PUT()).
 */
#define LDLM_LOCK_RELEASE(lock)          \
do {                                        \
        /*LDLM_DEBUG((lock), "put");*/    \
        ldlm_lock_put(lock);                \
} while (0)

#define LDLM_LOCK_GET(lock)                  \
({                                            \
        ldlm_lock_get(lock);                \
        /*LDLM_DEBUG((lock), "get");*/    \
        lock;                              \
})

#define ldlm_lock_list_put(head, member, count)              \
({                                                                \
        struct ldlm_lock *_lock, *_next;                            \
        int c = count;                                        \
        list_for_each_entry_safe(_lock, _next, head, member) {  \
                if (c-- == 0)                                  \
                        break;                                \
                list_del_init(&_lock->member);            \
                LDLM_LOCK_RELEASE(_lock);                          \
        }                                                          \
        LASSERT(c <= 0);                                            \
})

struct ldlm_lock *ldlm_lock_get(struct ldlm_lock *lock);
void ldlm_lock_put(struct ldlm_lock *lock);
void ldlm_lock2desc(struct ldlm_lock *lock, struct ldlm_lock_desc *desc);
void ldlm_lock_addref(const struct lustre_handle *lockh, __u32 mode);
int  ldlm_lock_addref_try(const struct lustre_handle *lockh, __u32 mode);
void ldlm_lock_decref(const struct lustre_handle *lockh, __u32 mode);
void ldlm_lock_decref_and_cancel(const struct lustre_handle *lockh, __u32 mode);
void ldlm_lock_fail_match_locked(struct ldlm_lock *lock);
void ldlm_lock_allow_match(struct ldlm_lock *lock);
void ldlm_lock_allow_match_locked(struct ldlm_lock *lock);
enum ldlm_mode ldlm_lock_match(struct ldlm_namespace *ns, __u64 flags,
                               const struct ldlm_res_id *,
                               enum ldlm_type type, ldlm_policy_data_t *,
                               enum ldlm_mode mode, struct lustre_handle *,
                               int unref);
enum ldlm_mode ldlm_revalidate_lock_handle(const struct lustre_handle *lockh,
                                           __u64 *bits);
void ldlm_lock_cancel(struct ldlm_lock *lock);
void ldlm_lock_dump_handle(int level, const struct lustre_handle *);
void ldlm_unlink_lock_skiplist(struct ldlm_lock *req);

/* resource.c */
struct ldlm_namespace *
ldlm_namespace_new(struct obd_device *obd, char *name,
                   ldlm_side_t client, enum ldlm_appetite apt,
                   enum ldlm_ns_type ns_type);
int ldlm_namespace_cleanup(struct ldlm_namespace *ns, __u64 flags);
void ldlm_namespace_get(struct ldlm_namespace *ns);
void ldlm_namespace_put(struct ldlm_namespace *ns);
int ldlm_debugfs_setup(void);
void ldlm_debugfs_cleanup(void);

/* resource.c - internal */
struct ldlm_resource *ldlm_resource_get(struct ldlm_namespace *ns,
                                        struct ldlm_resource *parent,
                                        const struct ldlm_res_id *,
                                        enum ldlm_type type, int create);
int ldlm_resource_putref(struct ldlm_resource *res);
void ldlm_resource_add_lock(struct ldlm_resource *res,
                            struct list_head *head,
                            struct ldlm_lock *lock);
void ldlm_resource_unlink_lock(struct ldlm_lock *lock);
void ldlm_res2desc(struct ldlm_resource *res, struct ldlm_resource_desc *desc);
void ldlm_dump_all_namespaces(ldlm_side_t client, int level);
void ldlm_namespace_dump(int level, struct ldlm_namespace *);
void ldlm_resource_dump(int level, struct ldlm_resource *);
int ldlm_lock_change_resource(struct ldlm_namespace *, struct ldlm_lock *,
                              const struct ldlm_res_id *);

#define LDLM_RESOURCE_ADDREF(res) do {                            \
        lu_ref_add_atomic(&(res)->lr_reference, __func__, current);  \
} while (0)

#define LDLM_RESOURCE_DELREF(res) do {                            \
        lu_ref_del(&(res)->lr_reference, __func__, current);      \
} while (0)

/* ldlm_request.c */
/** \defgroup ldlm_local_ast Default AST handlers for local locks
 * These AST handlers are typically used for server-side local locks and are
 * also used by client-side lock handlers to perform minimum level base
 * processing.
 * @{
 */
int ldlm_completion_ast_async(struct ldlm_lock *lock, __u64 flags, void *data);
int ldlm_completion_ast(struct ldlm_lock *lock, __u64 flags, void *data);
/** @} ldlm_local_ast */

/** \defgroup ldlm_cli_api API to operate on locks from actual LDLM users.
 * These are typically used by client and server (*_local versions)
 * to obtain and release locks.
 * @{
 */
int ldlm_cli_enqueue(struct obd_export *exp, struct ptlrpc_request **reqp,
                     struct ldlm_enqueue_info *einfo,
                     const struct ldlm_res_id *res_id,
                     ldlm_policy_data_t const *policy, __u64 *flags,
                     void *lvb, __u32 lvb_len, enum lvb_type lvb_type,
                     struct lustre_handle *lockh, int async);
int ldlm_prep_enqueue_req(struct obd_export *exp,
                          struct ptlrpc_request *req,
                          struct list_head *cancels,
                          int count);
int ldlm_prep_elc_req(struct obd_export *exp,
                      struct ptlrpc_request *req,
                      int version, int opc, int canceloff,
                      struct list_head *cancels, int count);

int ldlm_cli_enqueue_fini(struct obd_export *exp, struct ptlrpc_request *req,
                          enum ldlm_type type, __u8 with_policy,
                          enum ldlm_mode mode,
                          __u64 *flags, void *lvb, __u32 lvb_len,
                          const struct lustre_handle *lockh, int rc);
int ldlm_cli_update_pool(struct ptlrpc_request *req);
int ldlm_cli_cancel(const struct lustre_handle *lockh,
                    enum ldlm_cancel_flags cancel_flags);
int ldlm_cli_cancel_unused(struct ldlm_namespace *, const struct ldlm_res_id *,
                           enum ldlm_cancel_flags flags, void *opaque);
int ldlm_cli_cancel_unused_resource(struct ldlm_namespace *ns,
                                    const struct ldlm_res_id *res_id,
                                    ldlm_policy_data_t *policy,
                                    enum ldlm_mode mode,
                                    enum ldlm_cancel_flags flags,
                                    void *opaque);
int ldlm_cancel_resource_local(struct ldlm_resource *res,
                               struct list_head *cancels,
                               ldlm_policy_data_t *policy,
                               enum ldlm_mode mode, __u64 lock_flags,
                               enum ldlm_cancel_flags cancel_flags,
                               void *opaque);
int ldlm_cli_cancel_list_local(struct list_head *cancels, int count,
                               enum ldlm_cancel_flags flags);
int ldlm_cli_cancel_list(struct list_head *head, int count,
                         struct ptlrpc_request *req,
                         enum ldlm_cancel_flags flags);
/** @} ldlm_cli_api */

/* mds/handler.c */
/* This has to be here because recursive inclusion sucks. */
int intent_disposition(struct ldlm_reply *rep, int flag);
void intent_set_disposition(struct ldlm_reply *rep, int flag);

/**
 * "Modes" of acquiring lock_res, necessary to tell lockdep that taking more
 * than one lock_res is dead-lock safe.
 */
enum lock_res_type {
        LRT_NORMAL,
        LRT_NEW
};

/** Lock resource. */
static inline void lock_res(struct ldlm_resource *res)
{
        spin_lock(&res->lr_lock);
}

/** Lock resource with a way to instruct lockdep code about nestedness-safe. */
static inline void lock_res_nested(struct ldlm_resource *res,
                                   enum lock_res_type mode)
{
        spin_lock_nested(&res->lr_lock, mode);
}

/** Unlock resource. */
static inline void unlock_res(struct ldlm_resource *res)
{
        spin_unlock(&res->lr_lock);
}

/** Check if resource is already locked, assert if not. */
static inline void check_res_locked(struct ldlm_resource *res)
{
        assert_spin_locked(&res->lr_lock);
}

struct ldlm_resource *lock_res_and_lock(struct ldlm_lock *lock);
void unlock_res_and_lock(struct ldlm_lock *lock);

/* ldlm_pool.c */
/** \defgroup ldlm_pools Various LDLM pool related functions
 * There are not used outside of ldlm.
 * @{
 */
int ldlm_pools_init(void);
void ldlm_pools_fini(void);

int ldlm_pool_init(struct ldlm_pool *pl, struct ldlm_namespace *ns,
                   int idx, ldlm_side_t client);
void ldlm_pool_fini(struct ldlm_pool *pl);
void ldlm_pool_add(struct ldlm_pool *pl, struct ldlm_lock *lock);
void ldlm_pool_del(struct ldlm_pool *pl, struct ldlm_lock *lock);
/** @} */

#endif
/** @} LDLM */