Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0 */
2 : /*
3 : * include/linux/buffer_head.h
4 : *
5 : * Everything to do with buffer_heads.
6 : */
7 :
8 : #ifndef _LINUX_BUFFER_HEAD_H
9 : #define _LINUX_BUFFER_HEAD_H
10 :
11 : #include <linux/types.h>
12 : #include <linux/fs.h>
13 : #include <linux/linkage.h>
14 : #include <linux/pagemap.h>
15 : #include <linux/wait.h>
16 : #include <linux/atomic.h>
17 :
18 : #ifdef CONFIG_BLOCK
19 :
20 : enum bh_state_bits {
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 */
25 :
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 */
38 :
39 : BH_PrivateStart,/* not a state bit, but the first bit available
40 : * for private allocation by other entities
41 : */
42 : };
43 :
44 : #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)
45 :
46 : struct page;
47 : struct buffer_head;
48 : struct address_space;
49 : typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
50 :
51 : /*
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).
59 : */
60 : struct buffer_head {
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 */
64 :
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 */
68 :
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
74 : associated with */
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 */
79 : };
80 :
81 : /*
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.
86 : */
87 : #define BUFFER_FNS(bit, name) \
88 : static __always_inline void set_buffer_##name(struct buffer_head *bh) \
89 : { \
90 : if (!test_bit(BH_##bit, &(bh)->b_state)) \
91 : set_bit(BH_##bit, &(bh)->b_state); \
92 : } \
93 : static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
94 : { \
95 : clear_bit(BH_##bit, &(bh)->b_state); \
96 : } \
97 : static __always_inline int buffer_##name(const struct buffer_head *bh) \
98 : { \
99 : return test_bit(BH_##bit, &(bh)->b_state); \
100 : }
101 :
102 : /*
103 : * test_set_buffer_foo() and test_clear_buffer_foo()
104 : */
105 : #define TAS_BUFFER_FNS(bit, name) \
106 : static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
107 : { \
108 : return test_and_set_bit(BH_##bit, &(bh)->b_state); \
109 : } \
110 : static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
111 : { \
112 : return test_and_clear_bit(BH_##bit, &(bh)->b_state); \
113 : } \
114 :
115 : /*
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.
119 : */
120 0 : BUFFER_FNS(Uptodate, uptodate)
121 0 : BUFFER_FNS(Dirty, dirty)
122 0 : TAS_BUFFER_FNS(Dirty, dirty)
123 0 : BUFFER_FNS(Lock, locked)
124 0 : BUFFER_FNS(Req, req)
125 0 : TAS_BUFFER_FNS(Req, req)
126 0 : BUFFER_FNS(Mapped, mapped)
127 0 : BUFFER_FNS(New, new)
128 0 : BUFFER_FNS(Async_Read, async_read)
129 0 : BUFFER_FNS(Async_Write, async_write)
130 0 : BUFFER_FNS(Delay, delay)
131 0 : BUFFER_FNS(Boundary, boundary)
132 0 : BUFFER_FNS(Write_EIO, write_io_error)
133 0 : BUFFER_FNS(Unwritten, unwritten)
134 0 : BUFFER_FNS(Meta, meta)
135 0 : BUFFER_FNS(Prio, prio)
136 0 : BUFFER_FNS(Defer_Completion, defer_completion)
137 :
138 : #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK)
139 :
140 : /* If we *know* page->private refers to buffer_heads */
141 : #define page_buffers(page) \
142 : ({ \
143 : BUG_ON(!PagePrivate(page)); \
144 : ((struct buffer_head *)page_private(page)); \
145 : })
146 : #define page_has_buffers(page) PagePrivate(page)
147 : #define folio_buffers(folio) folio_get_private(folio)
148 :
149 : void buffer_check_dirty_writeback(struct page *page,
150 : bool *dirty, bool *writeback);
151 :
152 : /*
153 : * Declarations
154 : */
155 :
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 : int try_to_free_buffers(struct page *);
162 : struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
163 : bool retry);
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);
169 :
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,
177 : sector_t len);
178 : static inline void clean_bdev_bh_alias(struct buffer_head *bh)
179 : {
180 0 : clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
181 : }
182 :
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,
187 : unsigned size);
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,
194 : gfp_t gfp);
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);
213 :
214 : extern int buffer_heads_over_limit;
215 :
216 : /*
217 : * Generic address_space_operations implementations for buffer_head-backed
218 : * address_spaces.
219 : */
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_page(struct page*, 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 : unsigned flags, 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, 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)
249 : {
250 : if (err == 0)
251 : return VM_FAULT_LOCKED;
252 : if (err == -EFAULT || err == -EAGAIN)
253 : return VM_FAULT_NOPAGE;
254 : if (err == -ENOMEM)
255 : return VM_FAULT_OOM;
256 : /* -ENOSPC, -EDQUOT, -EIO ... */
257 : return VM_FAULT_SIGBUS;
258 : }
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, unsigned,
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);
269 :
270 : void buffer_init(void);
271 :
272 : /*
273 : * inline definitions
274 : */
275 :
276 : static inline void get_bh(struct buffer_head *bh)
277 : {
278 0 : atomic_inc(&bh->b_count);
279 : }
280 :
281 : static inline void put_bh(struct buffer_head *bh)
282 : {
283 0 : smp_mb__before_atomic();
284 0 : atomic_dec(&bh->b_count);
285 : }
286 :
287 0 : static inline void brelse(struct buffer_head *bh)
288 : {
289 0 : if (bh)
290 : __brelse(bh);
291 0 : }
292 :
293 : static inline void bforget(struct buffer_head *bh)
294 : {
295 : if (bh)
296 : __bforget(bh);
297 : }
298 :
299 : static inline struct buffer_head *
300 : sb_bread(struct super_block *sb, sector_t block)
301 : {
302 : return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
303 : }
304 :
305 : static inline struct buffer_head *
306 : sb_bread_unmovable(struct super_block *sb, sector_t block)
307 : {
308 : return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
309 : }
310 :
311 : static inline void
312 : sb_breadahead(struct super_block *sb, sector_t block)
313 : {
314 : __breadahead(sb->s_bdev, block, sb->s_blocksize);
315 : }
316 :
317 : static inline void
318 : sb_breadahead_unmovable(struct super_block *sb, sector_t block)
319 : {
320 : __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
321 : }
322 :
323 : static inline struct buffer_head *
324 : sb_getblk(struct super_block *sb, sector_t block)
325 : {
326 : return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
327 : }
328 :
329 :
330 : static inline struct buffer_head *
331 : sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
332 : {
333 : return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
334 : }
335 :
336 : static inline struct buffer_head *
337 : sb_find_get_block(struct super_block *sb, sector_t block)
338 : {
339 : return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
340 : }
341 :
342 : static inline void
343 : map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
344 : {
345 : set_buffer_mapped(bh);
346 : bh->b_bdev = sb->s_bdev;
347 : bh->b_blocknr = block;
348 : bh->b_size = sb->s_blocksize;
349 : }
350 :
351 : static inline void wait_on_buffer(struct buffer_head *bh)
352 : {
353 : might_sleep();
354 0 : if (buffer_locked(bh))
355 : __wait_on_buffer(bh);
356 : }
357 :
358 : static inline int trylock_buffer(struct buffer_head *bh)
359 : {
360 0 : return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
361 : }
362 :
363 : static inline void lock_buffer(struct buffer_head *bh)
364 : {
365 : might_sleep();
366 0 : if (!trylock_buffer(bh))
367 0 : __lock_buffer(bh);
368 : }
369 :
370 : static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
371 : sector_t block,
372 : unsigned size)
373 : {
374 : return __getblk_gfp(bdev, block, size, 0);
375 : }
376 :
377 : static inline struct buffer_head *__getblk(struct block_device *bdev,
378 : sector_t block,
379 : unsigned size)
380 : {
381 0 : return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
382 : }
383 :
384 : /**
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
389 : *
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.
393 : */
394 : static inline struct buffer_head *
395 : __bread(struct block_device *bdev, sector_t block, unsigned size)
396 : {
397 : return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
398 : }
399 :
400 : bool block_dirty_folio(struct address_space *mapping, struct folio *folio);
401 :
402 : #else /* CONFIG_BLOCK */
403 :
404 : static inline void buffer_init(void) {}
405 : static inline int try_to_free_buffers(struct page *page) { return 1; }
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
413 :
414 : #endif /* CONFIG_BLOCK */
415 : #endif /* _LINUX_BUFFER_HEAD_H */
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