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Linux/include/linux/buffer_head.h

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  1 /*
  2  * include/linux/buffer_head.h
  3  *
  4  * Everything to do with buffer_heads.
  5  */
  6 
  7 #ifndef _LINUX_BUFFER_HEAD_H
  8 #define _LINUX_BUFFER_HEAD_H
  9 
 10 #include <linux/types.h>
 11 #include <linux/fs.h>
 12 #include <linux/linkage.h>
 13 #include <linux/pagemap.h>
 14 #include <linux/wait.h>
 15 #include <linux/atomic.h>
 16 
 17 #ifdef CONFIG_BLOCK
 18 
 19 enum bh_state_bits {
 20         BH_Uptodate,    /* Contains valid data */
 21         BH_Dirty,       /* Is dirty */
 22         BH_Lock,        /* Is locked */
 23         BH_Req,         /* Has been submitted for I/O */
 24         BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
 25                           * IO completion of other buffers in the page
 26                           */
 27 
 28         BH_Mapped,      /* Has a disk mapping */
 29         BH_New,         /* Disk mapping was newly created by get_block */
 30         BH_Async_Read,  /* Is under end_buffer_async_read I/O */
 31         BH_Async_Write, /* Is under end_buffer_async_write I/O */
 32         BH_Delay,       /* Buffer is not yet allocated on disk */
 33         BH_Boundary,    /* Block is followed by a discontiguity */
 34         BH_Write_EIO,   /* I/O error on write */
 35         BH_Unwritten,   /* Buffer is allocated on disk but not written */
 36         BH_Quiet,       /* Buffer Error Prinks to be quiet */
 37         BH_Meta,        /* Buffer contains metadata */
 38         BH_Prio,        /* Buffer should be submitted with REQ_PRIO */
 39         BH_Defer_Completion, /* Defer AIO completion to workqueue */
 40 
 41         BH_PrivateStart,/* not a state bit, but the first bit available
 42                          * for private allocation by other entities
 43                          */
 44 };
 45 
 46 #define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512)
 47 
 48 struct page;
 49 struct buffer_head;
 50 struct address_space;
 51 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
 52 
 53 /*
 54  * Historically, a buffer_head was used to map a single block
 55  * within a page, and of course as the unit of I/O through the
 56  * filesystem and block layers.  Nowadays the basic I/O unit
 57  * is the bio, and buffer_heads are used for extracting block
 58  * mappings (via a get_block_t call), for tracking state within
 59  * a page (via a page_mapping) and for wrapping bio submission
 60  * for backward compatibility reasons (e.g. submit_bh).
 61  */
 62 struct buffer_head {
 63         unsigned long b_state;          /* buffer state bitmap (see above) */
 64         struct buffer_head *b_this_page;/* circular list of page's buffers */
 65         struct page *b_page;            /* the page this bh is mapped to */
 66 
 67         sector_t b_blocknr;             /* start block number */
 68         size_t b_size;                  /* size of mapping */
 69         char *b_data;                   /* pointer to data within the page */
 70 
 71         struct block_device *b_bdev;
 72         bh_end_io_t *b_end_io;          /* I/O completion */
 73         void *b_private;                /* reserved for b_end_io */
 74         struct list_head b_assoc_buffers; /* associated with another mapping */
 75         struct address_space *b_assoc_map;      /* mapping this buffer is
 76                                                    associated with */
 77         atomic_t b_count;               /* users using this buffer_head */
 78 };
 79 
 80 /*
 81  * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
 82  * and buffer_foo() functions.
 83  */
 84 #define BUFFER_FNS(bit, name)                                           \
 85 static inline void set_buffer_##name(struct buffer_head *bh)            \
 86 {                                                                       \
 87         set_bit(BH_##bit, &(bh)->b_state);                              \
 88 }                                                                       \
 89 static inline void clear_buffer_##name(struct buffer_head *bh)          \
 90 {                                                                       \
 91         clear_bit(BH_##bit, &(bh)->b_state);                            \
 92 }                                                                       \
 93 static inline int buffer_##name(const struct buffer_head *bh)           \
 94 {                                                                       \
 95         return test_bit(BH_##bit, &(bh)->b_state);                      \
 96 }
 97 
 98 /*
 99  * test_set_buffer_foo() and test_clear_buffer_foo()
100  */
101 #define TAS_BUFFER_FNS(bit, name)                                       \
102 static inline int test_set_buffer_##name(struct buffer_head *bh)        \
103 {                                                                       \
104         return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
105 }                                                                       \
106 static inline int test_clear_buffer_##name(struct buffer_head *bh)      \
107 {                                                                       \
108         return test_and_clear_bit(BH_##bit, &(bh)->b_state);            \
109 }                                                                       \
110 
111 /*
112  * Emit the buffer bitops functions.   Note that there are also functions
113  * of the form "mark_buffer_foo()".  These are higher-level functions which
114  * do something in addition to setting a b_state bit.
115  */
116 BUFFER_FNS(Uptodate, uptodate)
117 BUFFER_FNS(Dirty, dirty)
118 TAS_BUFFER_FNS(Dirty, dirty)
119 BUFFER_FNS(Lock, locked)
120 BUFFER_FNS(Req, req)
121 TAS_BUFFER_FNS(Req, req)
122 BUFFER_FNS(Mapped, mapped)
123 BUFFER_FNS(New, new)
124 BUFFER_FNS(Async_Read, async_read)
125 BUFFER_FNS(Async_Write, async_write)
126 BUFFER_FNS(Delay, delay)
127 BUFFER_FNS(Boundary, boundary)
128 BUFFER_FNS(Write_EIO, write_io_error)
129 BUFFER_FNS(Unwritten, unwritten)
130 BUFFER_FNS(Meta, meta)
131 BUFFER_FNS(Prio, prio)
132 BUFFER_FNS(Defer_Completion, defer_completion)
133 
134 #define bh_offset(bh)           ((unsigned long)(bh)->b_data & ~PAGE_MASK)
135 
136 /* If we *know* page->private refers to buffer_heads */
137 #define page_buffers(page)                                      \
138         ({                                                      \
139                 BUG_ON(!PagePrivate(page));                     \
140                 ((struct buffer_head *)page_private(page));     \
141         })
142 #define page_has_buffers(page)  PagePrivate(page)
143 
144 void buffer_check_dirty_writeback(struct page *page,
145                                      bool *dirty, bool *writeback);
146 
147 /*
148  * Declarations
149  */
150 
151 void mark_buffer_dirty(struct buffer_head *bh);
152 void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
153 void touch_buffer(struct buffer_head *bh);
154 void set_bh_page(struct buffer_head *bh,
155                 struct page *page, unsigned long offset);
156 int try_to_free_buffers(struct page *);
157 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
158                 int retry);
159 void create_empty_buffers(struct page *, unsigned long,
160                         unsigned long b_state);
161 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
162 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
163 void end_buffer_async_write(struct buffer_head *bh, int uptodate);
164 
165 /* Things to do with buffers at mapping->private_list */
166 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
167 int inode_has_buffers(struct inode *);
168 void invalidate_inode_buffers(struct inode *);
169 int remove_inode_buffers(struct inode *inode);
170 int sync_mapping_buffers(struct address_space *mapping);
171 void unmap_underlying_metadata(struct block_device *bdev, sector_t block);
172 
173 void mark_buffer_async_write(struct buffer_head *bh);
174 void __wait_on_buffer(struct buffer_head *);
175 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
176 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
177                         unsigned size);
178 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
179                                   unsigned size, gfp_t gfp);
180 void __brelse(struct buffer_head *);
181 void __bforget(struct buffer_head *);
182 void __breadahead(struct block_device *, sector_t block, unsigned int size);
183 struct buffer_head *__bread_gfp(struct block_device *,
184                                 sector_t block, unsigned size, gfp_t gfp);
185 void invalidate_bh_lrus(void);
186 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
187 void free_buffer_head(struct buffer_head * bh);
188 void unlock_buffer(struct buffer_head *bh);
189 void __lock_buffer(struct buffer_head *bh);
190 void ll_rw_block(int, int, struct buffer_head * bh[]);
191 int sync_dirty_buffer(struct buffer_head *bh);
192 int __sync_dirty_buffer(struct buffer_head *bh, int rw);
193 void write_dirty_buffer(struct buffer_head *bh, int rw);
194 int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags);
195 int submit_bh(int, struct buffer_head *);
196 void write_boundary_block(struct block_device *bdev,
197                         sector_t bblock, unsigned blocksize);
198 int bh_uptodate_or_lock(struct buffer_head *bh);
199 int bh_submit_read(struct buffer_head *bh);
200 
201 extern int buffer_heads_over_limit;
202 
203 /*
204  * Generic address_space_operations implementations for buffer_head-backed
205  * address_spaces.
206  */
207 void block_invalidatepage(struct page *page, unsigned int offset,
208                           unsigned int length);
209 int block_write_full_page(struct page *page, get_block_t *get_block,
210                                 struct writeback_control *wbc);
211 int block_read_full_page(struct page*, get_block_t*);
212 int block_is_partially_uptodate(struct page *page, unsigned long from,
213                                 unsigned long count);
214 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
215                 unsigned flags, struct page **pagep, get_block_t *get_block);
216 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
217                 get_block_t *get_block);
218 int block_write_end(struct file *, struct address_space *,
219                                 loff_t, unsigned, unsigned,
220                                 struct page *, void *);
221 int generic_write_end(struct file *, struct address_space *,
222                                 loff_t, unsigned, unsigned,
223                                 struct page *, void *);
224 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
225 int cont_write_begin(struct file *, struct address_space *, loff_t,
226                         unsigned, unsigned, struct page **, void **,
227                         get_block_t *, loff_t *);
228 int generic_cont_expand_simple(struct inode *inode, loff_t size);
229 int block_commit_write(struct page *page, unsigned from, unsigned to);
230 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
231                                 get_block_t get_block);
232 /* Convert errno to return value from ->page_mkwrite() call */
233 static inline int block_page_mkwrite_return(int err)
234 {
235         if (err == 0)
236                 return VM_FAULT_LOCKED;
237         if (err == -EFAULT)
238                 return VM_FAULT_NOPAGE;
239         if (err == -ENOMEM)
240                 return VM_FAULT_OOM;
241         if (err == -EAGAIN)
242                 return VM_FAULT_RETRY;
243         /* -ENOSPC, -EDQUOT, -EIO ... */
244         return VM_FAULT_SIGBUS;
245 }
246 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
247 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
248 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
249                                 struct page **, void **, get_block_t*);
250 int nobh_write_end(struct file *, struct address_space *,
251                                 loff_t, unsigned, unsigned,
252                                 struct page *, void *);
253 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
254 int nobh_writepage(struct page *page, get_block_t *get_block,
255                         struct writeback_control *wbc);
256 
257 void buffer_init(void);
258 
259 /*
260  * inline definitions
261  */
262 
263 static inline void attach_page_buffers(struct page *page,
264                 struct buffer_head *head)
265 {
266         page_cache_get(page);
267         SetPagePrivate(page);
268         set_page_private(page, (unsigned long)head);
269 }
270 
271 static inline void get_bh(struct buffer_head *bh)
272 {
273         atomic_inc(&bh->b_count);
274 }
275 
276 static inline void put_bh(struct buffer_head *bh)
277 {
278         smp_mb__before_atomic();
279         atomic_dec(&bh->b_count);
280 }
281 
282 static inline void brelse(struct buffer_head *bh)
283 {
284         if (bh)
285                 __brelse(bh);
286 }
287 
288 static inline void bforget(struct buffer_head *bh)
289 {
290         if (bh)
291                 __bforget(bh);
292 }
293 
294 static inline struct buffer_head *
295 sb_bread(struct super_block *sb, sector_t block)
296 {
297         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
298 }
299 
300 static inline struct buffer_head *
301 sb_bread_unmovable(struct super_block *sb, sector_t block)
302 {
303         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
304 }
305 
306 static inline void
307 sb_breadahead(struct super_block *sb, sector_t block)
308 {
309         __breadahead(sb->s_bdev, block, sb->s_blocksize);
310 }
311 
312 static inline struct buffer_head *
313 sb_getblk(struct super_block *sb, sector_t block)
314 {
315         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
316 }
317 
318 
319 static inline struct buffer_head *
320 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
321 {
322         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
323 }
324 
325 static inline struct buffer_head *
326 sb_find_get_block(struct super_block *sb, sector_t block)
327 {
328         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
329 }
330 
331 static inline void
332 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
333 {
334         set_buffer_mapped(bh);
335         bh->b_bdev = sb->s_bdev;
336         bh->b_blocknr = block;
337         bh->b_size = sb->s_blocksize;
338 }
339 
340 static inline void wait_on_buffer(struct buffer_head *bh)
341 {
342         might_sleep();
343         if (buffer_locked(bh))
344                 __wait_on_buffer(bh);
345 }
346 
347 static inline int trylock_buffer(struct buffer_head *bh)
348 {
349         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
350 }
351 
352 static inline void lock_buffer(struct buffer_head *bh)
353 {
354         might_sleep();
355         if (!trylock_buffer(bh))
356                 __lock_buffer(bh);
357 }
358 
359 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
360                                                    sector_t block,
361                                                    unsigned size)
362 {
363         return __getblk_gfp(bdev, block, size, 0);
364 }
365 
366 static inline struct buffer_head *__getblk(struct block_device *bdev,
367                                            sector_t block,
368                                            unsigned size)
369 {
370         return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
371 }
372 
373 /**
374  *  __bread() - reads a specified block and returns the bh
375  *  @bdev: the block_device to read from
376  *  @block: number of block
377  *  @size: size (in bytes) to read
378  *
379  *  Reads a specified block, and returns buffer head that contains it.
380  *  The page cache is allocated from movable area so that it can be migrated.
381  *  It returns NULL if the block was unreadable.
382  */
383 static inline struct buffer_head *
384 __bread(struct block_device *bdev, sector_t block, unsigned size)
385 {
386         return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
387 }
388 
389 extern int __set_page_dirty_buffers(struct page *page);
390 
391 #else /* CONFIG_BLOCK */
392 
393 static inline void buffer_init(void) {}
394 static inline int try_to_free_buffers(struct page *page) { return 1; }
395 static inline int inode_has_buffers(struct inode *inode) { return 0; }
396 static inline void invalidate_inode_buffers(struct inode *inode) {}
397 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
398 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
399 
400 #endif /* CONFIG_BLOCK */
401 #endif /* _LINUX_BUFFER_HEAD_H */
402 

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