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 <asm/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_Mapped, /* Has a disk mapping */
25 BH_New, /* Disk mapping was newly created by get_block */
26 BH_Async_Read, /* Is under end_buffer_async_read I/O */
27 BH_Async_Write, /* Is under end_buffer_async_write I/O */
28 BH_Delay, /* Buffer is not yet allocated on disk */
29 BH_Boundary, /* Block is followed by a discontiguity */
30 BH_Write_EIO, /* I/O error on write */
31 BH_Ordered, /* ordered write */
32 BH_Eopnotsupp, /* operation not supported (barrier) */
33 BH_Unwritten, /* Buffer is allocated on disk but not written */
34
35 BH_PrivateStart,/* not a state bit, but the first bit available
36 * for private allocation by other entities
37 */
38 };
39
40 #define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512)
41
42 struct page;
43 struct buffer_head;
44 struct address_space;
45 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
46
47 /*
48 * Historically, a buffer_head was used to map a single block
49 * within a page, and of course as the unit of I/O through the
50 * filesystem and block layers. Nowadays the basic I/O unit
51 * is the bio, and buffer_heads are used for extracting block
52 * mappings (via a get_block_t call), for tracking state within
53 * a page (via a page_mapping) and for wrapping bio submission
54 * for backward compatibility reasons (e.g. submit_bh).
55 */
56 struct buffer_head {
57 unsigned long b_state; /* buffer state bitmap (see above) */
58 struct buffer_head *b_this_page;/* circular list of page's buffers */
59 struct page *b_page; /* the page this bh is mapped to */
60
61 sector_t b_blocknr; /* start block number */
62 size_t b_size; /* size of mapping */
63 char *b_data; /* pointer to data within the page */
64
65 struct block_device *b_bdev;
66 bh_end_io_t *b_end_io; /* I/O completion */
67 void *b_private; /* reserved for b_end_io */
68 struct list_head b_assoc_buffers; /* associated with another mapping */
69 struct address_space *b_assoc_map; /* mapping this buffer is
70 associated with */
71 atomic_t b_count; /* users using this buffer_head */
72 spinlock_t b_uptodate_lock;
73 spinlock_t b_state_lock;
74 };
75
76 /*
77 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
78 * and buffer_foo() functions.
79 */
80 #define BUFFER_FNS(bit, name) \
81 static inline void set_buffer_##name(struct buffer_head *bh) \
82 { \
83 set_bit(BH_##bit, &(bh)->b_state); \
84 } \
85 static inline void clear_buffer_##name(struct buffer_head *bh) \
86 { \
87 clear_bit(BH_##bit, &(bh)->b_state); \
88 } \
89 static inline int buffer_##name(const struct buffer_head *bh) \
90 { \
91 return test_bit(BH_##bit, &(bh)->b_state); \
92 }
93
94 /*
95 * test_set_buffer_foo() and test_clear_buffer_foo()
96 */
97 #define TAS_BUFFER_FNS(bit, name) \
98 static inline int test_set_buffer_##name(struct buffer_head *bh) \
99 { \
100 return test_and_set_bit(BH_##bit, &(bh)->b_state); \
101 } \
102 static inline int test_clear_buffer_##name(struct buffer_head *bh) \
103 { \
104 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \
105 } \
106
107 /*
108 * Emit the buffer bitops functions. Note that there are also functions
109 * of the form "mark_buffer_foo()". These are higher-level functions which
110 * do something in addition to setting a b_state bit.
111 */
112 BUFFER_FNS(Uptodate, uptodate)
113 BUFFER_FNS(Dirty, dirty)
114 TAS_BUFFER_FNS(Dirty, dirty)
115 BUFFER_FNS(Lock, locked)
116 TAS_BUFFER_FNS(Lock, locked)
117 BUFFER_FNS(Req, req)
118 TAS_BUFFER_FNS(Req, req)
119 BUFFER_FNS(Mapped, mapped)
120 BUFFER_FNS(New, new)
121 BUFFER_FNS(Async_Read, async_read)
122 BUFFER_FNS(Async_Write, async_write)
123 BUFFER_FNS(Delay, delay)
124 BUFFER_FNS(Boundary, boundary)
125 BUFFER_FNS(Write_EIO, write_io_error)
126 BUFFER_FNS(Ordered, ordered)
127 BUFFER_FNS(Eopnotsupp, eopnotsupp)
128 BUFFER_FNS(Unwritten, unwritten)
129
130 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK)
131 #define touch_buffer(bh) mark_page_accessed(bh->b_page)
132
133 /* If we *know* page->private refers to buffer_heads */
134 #define page_buffers(page) \
135 ({ \
136 BUG_ON(!PagePrivate(page)); \
137 ((struct buffer_head *)page_private(page)); \
138 })
139 #define page_has_buffers(page) PagePrivate(page)
140
141 /*
142 * Declarations
143 */
144
145 void mark_buffer_dirty(struct buffer_head *bh);
146 void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
147 void set_bh_page(struct buffer_head *bh,
148 struct page *page, unsigned long offset);
149 int try_to_free_buffers(struct page *);
150 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
151 int retry);
152 void create_empty_buffers(struct page *, unsigned long,
153 unsigned long b_state);
154 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
155 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
156
157 /* Things to do with buffers at mapping->private_list */
158 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
159 int inode_has_buffers(struct inode *);
160 void invalidate_inode_buffers(struct inode *);
161 int remove_inode_buffers(struct inode *inode);
162 int sync_mapping_buffers(struct address_space *mapping);
163 void unmap_underlying_metadata(struct block_device *bdev, sector_t block);
164
165 void mark_buffer_async_write(struct buffer_head *bh);
166 void invalidate_bdev(struct block_device *);
167 int sync_blockdev(struct block_device *bdev);
168 void __wait_on_buffer(struct buffer_head *);
169 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
170 int fsync_bdev(struct block_device *);
171 struct super_block *freeze_bdev(struct block_device *);
172 void thaw_bdev(struct block_device *, struct super_block *);
173 int fsync_super(struct super_block *);
174 int fsync_no_super(struct block_device *);
175 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
176 unsigned size);
177 struct buffer_head *__getblk(struct block_device *bdev, sector_t block,
178 unsigned size);
179 void __brelse(struct buffer_head *);
180 void __bforget(struct buffer_head *);
181 void __breadahead(struct block_device *, sector_t block, unsigned int size);
182 struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size);
183 void invalidate_bh_lrus(void);
184 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
185 void free_buffer_head(struct buffer_head * bh);
186 void unlock_buffer(struct buffer_head *bh);
187 void __lock_buffer(struct buffer_head *bh);
188 void ll_rw_block(int, int, struct buffer_head * bh[]);
189 int sync_dirty_buffer(struct buffer_head *bh);
190 int submit_bh(int, struct buffer_head *);
191 void write_boundary_block(struct block_device *bdev,
192 sector_t bblock, unsigned blocksize);
193 int bh_uptodate_or_lock(struct buffer_head *bh);
194 int bh_submit_read(struct buffer_head *bh);
195
196 extern int buffer_heads_over_limit;
197
198 /*
199 * Generic address_space_operations implementations for buffer_head-backed
200 * address_spaces.
201 */
202 void block_invalidatepage(struct page *page, unsigned long offset);
203 int block_write_full_page(struct page *page, get_block_t *get_block,
204 struct writeback_control *wbc);
205 int block_read_full_page(struct page*, get_block_t*);
206 int block_write_begin(struct file *, struct address_space *,
207 loff_t, unsigned, unsigned,
208 struct page **, void **, get_block_t*);
209 int block_write_end(struct file *, struct address_space *,
210 loff_t, unsigned, unsigned,
211 struct page *, void *);
212 int generic_write_end(struct file *, struct address_space *,
213 loff_t, unsigned, unsigned,
214 struct page *, void *);
215 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
216 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
217 int cont_write_begin(struct file *, struct address_space *, loff_t,
218 unsigned, unsigned, struct page **, void **,
219 get_block_t *, loff_t *);
220 int generic_cont_expand_simple(struct inode *inode, loff_t size);
221 int block_commit_write(struct page *page, unsigned from, unsigned to);
222 int block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
223 get_block_t get_block);
224 void block_sync_page(struct page *);
225 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
226 int generic_commit_write(struct file *, struct page *, unsigned, unsigned);
227 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
228 int file_fsync(struct file *, struct dentry *, int);
229 int nobh_write_begin(struct file *, struct address_space *,
230 loff_t, unsigned, unsigned,
231 struct page **, void **, get_block_t*);
232 int nobh_write_end(struct file *, struct address_space *,
233 loff_t, unsigned, unsigned,
234 struct page *, void *);
235 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
236 int nobh_writepage(struct page *page, get_block_t *get_block,
237 struct writeback_control *wbc);
238
239 void buffer_init(void);
240
241 /*
242 * inline definitions
243 */
244
245 static inline void attach_page_buffers(struct page *page,
246 struct buffer_head *head)
247 {
248 page_cache_get(page);
249 SetPagePrivate(page);
250 set_page_private(page, (unsigned long)head);
251 }
252
253 static inline void get_bh(struct buffer_head *bh)
254 {
255 atomic_inc(&bh->b_count);
256 }
257
258 static inline void put_bh(struct buffer_head *bh)
259 {
260 smp_mb__before_atomic_dec();
261 atomic_dec(&bh->b_count);
262 }
263
264 static inline void brelse(struct buffer_head *bh)
265 {
266 if (bh)
267 __brelse(bh);
268 }
269
270 static inline void bforget(struct buffer_head *bh)
271 {
272 if (bh)
273 __bforget(bh);
274 }
275
276 static inline struct buffer_head *
277 sb_bread(struct super_block *sb, sector_t block)
278 {
279 return __bread(sb->s_bdev, block, sb->s_blocksize);
280 }
281
282 static inline void
283 sb_breadahead(struct super_block *sb, sector_t block)
284 {
285 __breadahead(sb->s_bdev, block, sb->s_blocksize);
286 }
287
288 static inline struct buffer_head *
289 sb_getblk(struct super_block *sb, sector_t block)
290 {
291 return __getblk(sb->s_bdev, block, sb->s_blocksize);
292 }
293
294 static inline struct buffer_head *
295 sb_find_get_block(struct super_block *sb, sector_t block)
296 {
297 return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
298 }
299
300 static inline void
301 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
302 {
303 set_buffer_mapped(bh);
304 bh->b_bdev = sb->s_bdev;
305 bh->b_blocknr = block;
306 bh->b_size = sb->s_blocksize;
307 }
308
309 /*
310 * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into
311 * __wait_on_buffer() just to trip a debug check. Because debug code in inline
312 * functions is bloaty.
313 */
314 static inline void wait_on_buffer(struct buffer_head *bh)
315 {
316 might_sleep();
317 if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0)
318 __wait_on_buffer(bh);
319 }
320
321 static inline void lock_buffer(struct buffer_head *bh)
322 {
323 might_sleep();
324 if (test_set_buffer_locked(bh))
325 __lock_buffer(bh);
326 }
327
328 extern int __set_page_dirty_buffers(struct page *page);
329
330 #else /* CONFIG_BLOCK */
331
332 static inline void buffer_init(void) {}
333 static inline int try_to_free_buffers(struct page *page) { return 1; }
334 static inline int sync_blockdev(struct block_device *bdev) { return 0; }
335 static inline int inode_has_buffers(struct inode *inode) { return 0; }
336 static inline void invalidate_inode_buffers(struct inode *inode) {}
337 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
338 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
339 static inline void invalidate_bdev(struct block_device *bdev) {}
340
341
342 #endif /* CONFIG_BLOCK */
343 #endif /* _LINUX_BUFFER_HEAD_H */
344
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