1 /* SPDX-License-Identifier: GPL-2.0 */
3 * include/linux/buffer_head.h
5 * Everything to do with buffer_heads.
8 #ifndef _LINUX_BUFFER_HEAD_H
9 #define _LINUX_BUFFER_HEAD_H
11 #include <linux/types.h>
13 #include <linux/linkage.h>
14 #include <linux/pagemap.h>
15 #include <linux/wait.h>
16 #include <linux/atomic.h>
21 BH_Uptodate, /* Contains valid data */
22 BH_Dirty, /* Is dirty */
23 BH_Lock, /* Is locked */
24 BH_Req, /* Has been submitted for I/O */
26 BH_Mapped, /* Has a disk mapping */
27 BH_New, /* Disk mapping was newly created by get_block */
28 BH_Async_Read, /* Is under end_buffer_async_read I/O */
29 BH_Async_Write, /* Is under end_buffer_async_write I/O */
30 BH_Delay, /* Buffer is not yet allocated on disk */
31 BH_Boundary, /* Block is followed by a discontiguity */
32 BH_Write_EIO, /* I/O error on write */
33 BH_Unwritten, /* Buffer is allocated on disk but not written */
34 BH_Quiet, /* Buffer Error Prinks to be quiet */
35 BH_Meta, /* Buffer contains metadata */
36 BH_Prio, /* Buffer should be submitted with REQ_PRIO */
37 BH_Defer_Completion, /* Defer AIO completion to workqueue */
39 BH_PrivateStart,/* not a state bit, but the first bit available
40 * for private allocation by other entities
44 #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)
49 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
52 * Historically, a buffer_head was used to map a single block
53 * within a page, and of course as the unit of I/O through the
54 * filesystem and block layers. Nowadays the basic I/O unit
55 * is the bio, and buffer_heads are used for extracting block
56 * mappings (via a get_block_t call), for tracking state within
57 * a page (via a page_mapping) and for wrapping bio submission
58 * for backward compatibility reasons (e.g. submit_bh).
61 unsigned long b_state; /* buffer state bitmap (see above) */
62 struct buffer_head *b_this_page;/* circular list of page's buffers */
63 struct page *b_page; /* the page this bh is mapped to */
65 sector_t b_blocknr; /* start block number */
66 size_t b_size; /* size of mapping */
67 char *b_data; /* pointer to data within the page */
69 struct block_device *b_bdev;
70 bh_end_io_t *b_end_io; /* I/O completion */
71 void *b_private; /* reserved for b_end_io */
72 struct list_head b_assoc_buffers; /* associated with another mapping */
73 struct address_space *b_assoc_map; /* mapping this buffer is
75 atomic_t b_count; /* users using this buffer_head */
76 spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to
77 * serialise IO completion of other
78 * buffers in the page */
82 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
83 * and buffer_foo() functions.
84 * To avoid reset buffer flags that are already set, because that causes
85 * a costly cache line transition, check the flag first.
87 #define BUFFER_FNS(bit, name) \
88 static __always_inline void set_buffer_##name(struct buffer_head *bh) \
90 if (!test_bit(BH_##bit, &(bh)->b_state)) \
91 set_bit(BH_##bit, &(bh)->b_state); \
93 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
95 clear_bit(BH_##bit, &(bh)->b_state); \
97 static __always_inline int buffer_##name(const struct buffer_head *bh) \
99 return test_bit(BH_##bit, &(bh)->b_state); \
103 * test_set_buffer_foo() and test_clear_buffer_foo()
105 #define TAS_BUFFER_FNS(bit, name) \
106 static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
108 return test_and_set_bit(BH_##bit, &(bh)->b_state); \
110 static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
112 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \
116 * Emit the buffer bitops functions. Note that there are also functions
117 * of the form "mark_buffer_foo()". These are higher-level functions which
118 * do something in addition to setting a b_state bit.
120 BUFFER_FNS(Dirty, dirty)
121 TAS_BUFFER_FNS(Dirty, dirty)
122 BUFFER_FNS(Lock, locked)
124 TAS_BUFFER_FNS(Req, req)
125 BUFFER_FNS(Mapped, mapped)
127 BUFFER_FNS(Async_Read, async_read)
128 BUFFER_FNS(Async_Write, async_write)
129 BUFFER_FNS(Delay, delay)
130 BUFFER_FNS(Boundary, boundary)
131 BUFFER_FNS(Write_EIO, write_io_error)
132 BUFFER_FNS(Unwritten, unwritten)
133 BUFFER_FNS(Meta, meta)
134 BUFFER_FNS(Prio, prio)
135 BUFFER_FNS(Defer_Completion, defer_completion)
137 static __always_inline void set_buffer_uptodate(struct buffer_head *bh)
140 * If somebody else already set this uptodate, they will
141 * have done the memory barrier, and a reader will thus
142 * see *some* valid buffer state.
144 * Any other serialization (with IO errors or whatever that
145 * might clear the bit) has to come from other state (eg BH_Lock).
147 if (test_bit(BH_Uptodate, &bh->b_state))
151 * make it consistent with folio_mark_uptodate
152 * pairs with smp_load_acquire in buffer_uptodate
154 smp_mb__before_atomic();
155 set_bit(BH_Uptodate, &bh->b_state);
158 static __always_inline void clear_buffer_uptodate(struct buffer_head *bh)
160 clear_bit(BH_Uptodate, &bh->b_state);
163 static __always_inline int buffer_uptodate(const struct buffer_head *bh)
166 * make it consistent with folio_test_uptodate
167 * pairs with smp_mb__before_atomic in set_buffer_uptodate
169 return (smp_load_acquire(&bh->b_state) & (1UL << BH_Uptodate)) != 0;
172 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK)
174 /* If we *know* page->private refers to buffer_heads */
175 #define page_buffers(page) \
177 BUG_ON(!PagePrivate(page)); \
178 ((struct buffer_head *)page_private(page)); \
180 #define page_has_buffers(page) PagePrivate(page)
182 void buffer_check_dirty_writeback(struct page *page,
183 bool *dirty, bool *writeback);
189 void mark_buffer_dirty(struct buffer_head *bh);
190 void mark_buffer_write_io_error(struct buffer_head *bh);
191 void touch_buffer(struct buffer_head *bh);
192 void set_bh_page(struct buffer_head *bh,
193 struct page *page, unsigned long offset);
194 int try_to_free_buffers(struct page *);
195 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
197 void create_empty_buffers(struct page *, unsigned long,
198 unsigned long b_state);
199 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
200 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
201 void end_buffer_async_write(struct buffer_head *bh, int uptodate);
203 /* Things to do with buffers at mapping->private_list */
204 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
205 int inode_has_buffers(struct inode *);
206 void invalidate_inode_buffers(struct inode *);
207 int remove_inode_buffers(struct inode *inode);
208 int sync_mapping_buffers(struct address_space *mapping);
209 void clean_bdev_aliases(struct block_device *bdev, sector_t block,
211 static inline void clean_bdev_bh_alias(struct buffer_head *bh)
213 clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
216 void mark_buffer_async_write(struct buffer_head *bh);
217 void __wait_on_buffer(struct buffer_head *);
218 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
219 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
221 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
222 unsigned size, gfp_t gfp);
223 void __brelse(struct buffer_head *);
224 void __bforget(struct buffer_head *);
225 void __breadahead(struct block_device *, sector_t block, unsigned int size);
226 void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size,
228 struct buffer_head *__bread_gfp(struct block_device *,
229 sector_t block, unsigned size, gfp_t gfp);
230 void invalidate_bh_lrus(void);
231 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
232 void free_buffer_head(struct buffer_head * bh);
233 void unlock_buffer(struct buffer_head *bh);
234 void __lock_buffer(struct buffer_head *bh);
235 void ll_rw_block(int, int, int, struct buffer_head * bh[]);
236 int sync_dirty_buffer(struct buffer_head *bh);
237 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
238 void write_dirty_buffer(struct buffer_head *bh, int op_flags);
239 int submit_bh(int, int, struct buffer_head *);
240 void write_boundary_block(struct block_device *bdev,
241 sector_t bblock, unsigned blocksize);
242 int bh_uptodate_or_lock(struct buffer_head *bh);
243 int bh_submit_read(struct buffer_head *bh);
245 extern int buffer_heads_over_limit;
248 * Generic address_space_operations implementations for buffer_head-backed
251 void block_invalidatepage(struct page *page, unsigned int offset,
252 unsigned int length);
253 int block_write_full_page(struct page *page, get_block_t *get_block,
254 struct writeback_control *wbc);
255 int __block_write_full_page(struct inode *inode, struct page *page,
256 get_block_t *get_block, struct writeback_control *wbc,
257 bh_end_io_t *handler);
258 int block_read_full_page(struct page*, get_block_t*);
259 int block_is_partially_uptodate(struct page *page, unsigned long from,
260 unsigned long count);
261 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
262 unsigned flags, struct page **pagep, get_block_t *get_block);
263 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
264 get_block_t *get_block);
265 int block_write_end(struct file *, struct address_space *,
266 loff_t, unsigned, unsigned,
267 struct page *, void *);
268 int generic_write_end(struct file *, struct address_space *,
269 loff_t, unsigned, unsigned,
270 struct page *, void *);
271 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
272 void clean_page_buffers(struct page *page);
273 int cont_write_begin(struct file *, struct address_space *, loff_t,
274 unsigned, unsigned, struct page **, void **,
275 get_block_t *, loff_t *);
276 int generic_cont_expand_simple(struct inode *inode, loff_t size);
277 int block_commit_write(struct page *page, unsigned from, unsigned to);
278 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
279 get_block_t get_block);
280 /* Convert errno to return value from ->page_mkwrite() call */
281 static inline vm_fault_t block_page_mkwrite_return(int err)
284 return VM_FAULT_LOCKED;
285 if (err == -EFAULT || err == -EAGAIN)
286 return VM_FAULT_NOPAGE;
289 /* -ENOSPC, -EDQUOT, -EIO ... */
290 return VM_FAULT_SIGBUS;
292 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
293 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
294 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
295 struct page **, void **, get_block_t*);
296 int nobh_write_end(struct file *, struct address_space *,
297 loff_t, unsigned, unsigned,
298 struct page *, void *);
299 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
300 int nobh_writepage(struct page *page, get_block_t *get_block,
301 struct writeback_control *wbc);
303 void buffer_init(void);
309 static inline void get_bh(struct buffer_head *bh)
311 atomic_inc(&bh->b_count);
314 static inline void put_bh(struct buffer_head *bh)
316 smp_mb__before_atomic();
317 atomic_dec(&bh->b_count);
320 static inline void brelse(struct buffer_head *bh)
326 static inline void bforget(struct buffer_head *bh)
332 static inline struct buffer_head *
333 sb_bread(struct super_block *sb, sector_t block)
335 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
338 static inline struct buffer_head *
339 sb_bread_unmovable(struct super_block *sb, sector_t block)
341 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
345 sb_breadahead(struct super_block *sb, sector_t block)
347 __breadahead(sb->s_bdev, block, sb->s_blocksize);
351 sb_breadahead_unmovable(struct super_block *sb, sector_t block)
353 __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
356 static inline struct buffer_head *
357 sb_getblk(struct super_block *sb, sector_t block)
359 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
363 static inline struct buffer_head *
364 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
366 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
369 static inline struct buffer_head *
370 sb_find_get_block(struct super_block *sb, sector_t block)
372 return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
376 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
378 set_buffer_mapped(bh);
379 bh->b_bdev = sb->s_bdev;
380 bh->b_blocknr = block;
381 bh->b_size = sb->s_blocksize;
384 static inline void wait_on_buffer(struct buffer_head *bh)
387 if (buffer_locked(bh))
388 __wait_on_buffer(bh);
391 static inline int trylock_buffer(struct buffer_head *bh)
393 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
396 static inline void lock_buffer(struct buffer_head *bh)
399 if (!trylock_buffer(bh))
403 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
407 return __getblk_gfp(bdev, block, size, 0);
410 static inline struct buffer_head *__getblk(struct block_device *bdev,
414 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
418 * __bread() - reads a specified block and returns the bh
419 * @bdev: the block_device to read from
420 * @block: number of block
421 * @size: size (in bytes) to read
423 * Reads a specified block, and returns buffer head that contains it.
424 * The page cache is allocated from movable area so that it can be migrated.
425 * It returns NULL if the block was unreadable.
427 static inline struct buffer_head *
428 __bread(struct block_device *bdev, sector_t block, unsigned size)
430 return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
433 extern int __set_page_dirty_buffers(struct page *page);
435 #else /* CONFIG_BLOCK */
437 static inline void buffer_init(void) {}
438 static inline int try_to_free_buffers(struct page *page) { return 1; }
439 static inline int inode_has_buffers(struct inode *inode) { return 0; }
440 static inline void invalidate_inode_buffers(struct inode *inode) {}
441 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
442 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
443 #define buffer_heads_over_limit 0
445 #endif /* CONFIG_BLOCK */
446 #endif /* _LINUX_BUFFER_HEAD_H */