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(Uptodate, uptodate)
121 BUFFER_FNS(Dirty, dirty)
122 TAS_BUFFER_FNS(Dirty, dirty)
123 BUFFER_FNS(Lock, locked)
125 TAS_BUFFER_FNS(Req, req)
126 BUFFER_FNS(Mapped, mapped)
128 BUFFER_FNS(Async_Read, async_read)
129 BUFFER_FNS(Async_Write, async_write)
130 BUFFER_FNS(Delay, delay)
131 BUFFER_FNS(Boundary, boundary)
132 BUFFER_FNS(Write_EIO, write_io_error)
133 BUFFER_FNS(Unwritten, unwritten)
134 BUFFER_FNS(Meta, meta)
135 BUFFER_FNS(Prio, prio)
136 BUFFER_FNS(Defer_Completion, defer_completion)
138 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK)
140 /* If we *know* page->private refers to buffer_heads */
141 #define page_buffers(page) \
143 BUG_ON(!PagePrivate(page)); \
144 ((struct buffer_head *)page_private(page)); \
146 #define page_has_buffers(page) PagePrivate(page)
147 #define folio_buffers(folio) folio_get_private(folio)
149 void buffer_check_dirty_writeback(struct folio *folio,
150 bool *dirty, bool *writeback);
156 void mark_buffer_dirty(struct buffer_head *bh);
157 void mark_buffer_write_io_error(struct buffer_head *bh);
158 void touch_buffer(struct buffer_head *bh);
159 void set_bh_page(struct buffer_head *bh,
160 struct page *page, unsigned long offset);
161 bool try_to_free_buffers(struct folio *);
162 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
164 void create_empty_buffers(struct page *, unsigned long,
165 unsigned long b_state);
166 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
167 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
168 void end_buffer_async_write(struct buffer_head *bh, int uptodate);
170 /* Things to do with buffers at mapping->private_list */
171 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
172 int inode_has_buffers(struct inode *);
173 void invalidate_inode_buffers(struct inode *);
174 int remove_inode_buffers(struct inode *inode);
175 int sync_mapping_buffers(struct address_space *mapping);
176 void clean_bdev_aliases(struct block_device *bdev, sector_t block,
178 static inline void clean_bdev_bh_alias(struct buffer_head *bh)
180 clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
183 void mark_buffer_async_write(struct buffer_head *bh);
184 void __wait_on_buffer(struct buffer_head *);
185 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
186 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
188 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
189 unsigned size, gfp_t gfp);
190 void __brelse(struct buffer_head *);
191 void __bforget(struct buffer_head *);
192 void __breadahead(struct block_device *, sector_t block, unsigned int size);
193 void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size,
195 struct buffer_head *__bread_gfp(struct block_device *,
196 sector_t block, unsigned size, gfp_t gfp);
197 void invalidate_bh_lrus(void);
198 void invalidate_bh_lrus_cpu(void);
199 bool has_bh_in_lru(int cpu, void *dummy);
200 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
201 void free_buffer_head(struct buffer_head * bh);
202 void unlock_buffer(struct buffer_head *bh);
203 void __lock_buffer(struct buffer_head *bh);
204 void ll_rw_block(int, int, int, struct buffer_head * bh[]);
205 int sync_dirty_buffer(struct buffer_head *bh);
206 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
207 void write_dirty_buffer(struct buffer_head *bh, int op_flags);
208 int submit_bh(int, int, struct buffer_head *);
209 void write_boundary_block(struct block_device *bdev,
210 sector_t bblock, unsigned blocksize);
211 int bh_uptodate_or_lock(struct buffer_head *bh);
212 int bh_submit_read(struct buffer_head *bh);
214 extern int buffer_heads_over_limit;
217 * Generic address_space_operations implementations for buffer_head-backed
220 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length);
221 int block_write_full_page(struct page *page, get_block_t *get_block,
222 struct writeback_control *wbc);
223 int __block_write_full_page(struct inode *inode, struct page *page,
224 get_block_t *get_block, struct writeback_control *wbc,
225 bh_end_io_t *handler);
226 int block_read_full_folio(struct folio *, get_block_t *);
227 bool block_is_partially_uptodate(struct folio *, size_t from, size_t count);
228 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
229 struct page **pagep, get_block_t *get_block);
230 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
231 get_block_t *get_block);
232 int block_write_end(struct file *, struct address_space *,
233 loff_t, unsigned, unsigned,
234 struct page *, void *);
235 int generic_write_end(struct file *, struct address_space *,
236 loff_t, unsigned, unsigned,
237 struct page *, void *);
238 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
239 void clean_page_buffers(struct page *page);
240 int cont_write_begin(struct file *, struct address_space *, loff_t,
241 unsigned, struct page **, void **,
242 get_block_t *, loff_t *);
243 int generic_cont_expand_simple(struct inode *inode, loff_t size);
244 int block_commit_write(struct page *page, unsigned from, unsigned to);
245 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
246 get_block_t get_block);
247 /* Convert errno to return value from ->page_mkwrite() call */
248 static inline vm_fault_t block_page_mkwrite_return(int err)
251 return VM_FAULT_LOCKED;
252 if (err == -EFAULT || err == -EAGAIN)
253 return VM_FAULT_NOPAGE;
256 /* -ENOSPC, -EDQUOT, -EIO ... */
257 return VM_FAULT_SIGBUS;
259 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
260 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
261 int nobh_write_begin(struct address_space *, loff_t, unsigned len,
262 struct page **, void **, get_block_t*);
263 int nobh_write_end(struct file *, struct address_space *,
264 loff_t, unsigned, unsigned,
265 struct page *, void *);
266 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
267 int nobh_writepage(struct page *page, get_block_t *get_block,
268 struct writeback_control *wbc);
270 void buffer_init(void);
276 static inline void get_bh(struct buffer_head *bh)
278 atomic_inc(&bh->b_count);
281 static inline void put_bh(struct buffer_head *bh)
283 smp_mb__before_atomic();
284 atomic_dec(&bh->b_count);
287 static inline void brelse(struct buffer_head *bh)
293 static inline void bforget(struct buffer_head *bh)
299 static inline struct buffer_head *
300 sb_bread(struct super_block *sb, sector_t block)
302 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
305 static inline struct buffer_head *
306 sb_bread_unmovable(struct super_block *sb, sector_t block)
308 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
312 sb_breadahead(struct super_block *sb, sector_t block)
314 __breadahead(sb->s_bdev, block, sb->s_blocksize);
318 sb_breadahead_unmovable(struct super_block *sb, sector_t block)
320 __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
323 static inline struct buffer_head *
324 sb_getblk(struct super_block *sb, sector_t block)
326 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
330 static inline struct buffer_head *
331 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
333 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
336 static inline struct buffer_head *
337 sb_find_get_block(struct super_block *sb, sector_t block)
339 return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
343 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
345 set_buffer_mapped(bh);
346 bh->b_bdev = sb->s_bdev;
347 bh->b_blocknr = block;
348 bh->b_size = sb->s_blocksize;
351 static inline void wait_on_buffer(struct buffer_head *bh)
354 if (buffer_locked(bh))
355 __wait_on_buffer(bh);
358 static inline int trylock_buffer(struct buffer_head *bh)
360 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
363 static inline void lock_buffer(struct buffer_head *bh)
366 if (!trylock_buffer(bh))
370 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
374 return __getblk_gfp(bdev, block, size, 0);
377 static inline struct buffer_head *__getblk(struct block_device *bdev,
381 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
385 * __bread() - reads a specified block and returns the bh
386 * @bdev: the block_device to read from
387 * @block: number of block
388 * @size: size (in bytes) to read
390 * Reads a specified block, and returns buffer head that contains it.
391 * The page cache is allocated from movable area so that it can be migrated.
392 * It returns NULL if the block was unreadable.
394 static inline struct buffer_head *
395 __bread(struct block_device *bdev, sector_t block, unsigned size)
397 return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
400 bool block_dirty_folio(struct address_space *mapping, struct folio *folio);
402 #else /* CONFIG_BLOCK */
404 static inline void buffer_init(void) {}
405 static inline bool try_to_free_buffers(struct folio *folio) { return true; }
406 static inline int inode_has_buffers(struct inode *inode) { return 0; }
407 static inline void invalidate_inode_buffers(struct inode *inode) {}
408 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
409 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
410 static inline void invalidate_bh_lrus_cpu(void) {}
411 static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; }
412 #define buffer_heads_over_limit 0
414 #endif /* CONFIG_BLOCK */
415 #endif /* _LINUX_BUFFER_HEAD_H */