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TOMOYO Linux Cross Reference
Linux/fs/sync.c

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  1 /*
  2  * High-level sync()-related operations
  3  */
  4 
  5 #include <linux/kernel.h>
  6 #include <linux/file.h>
  7 #include <linux/fs.h>
  8 #include <linux/slab.h>
  9 #include <linux/export.h>
 10 #include <linux/namei.h>
 11 #include <linux/sched.h>
 12 #include <linux/writeback.h>
 13 #include <linux/syscalls.h>
 14 #include <linux/linkage.h>
 15 #include <linux/pagemap.h>
 16 #include <linux/quotaops.h>
 17 #include <linux/backing-dev.h>
 18 #include "internal.h"
 19 
 20 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
 21                         SYNC_FILE_RANGE_WAIT_AFTER)
 22 
 23 /*
 24  * Do the filesystem syncing work. For simple filesystems
 25  * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
 26  * submit IO for these buffers via __sync_blockdev(). This also speeds up the
 27  * wait == 1 case since in that case write_inode() functions do
 28  * sync_dirty_buffer() and thus effectively write one block at a time.
 29  */
 30 static int __sync_filesystem(struct super_block *sb, int wait)
 31 {
 32         if (wait)
 33                 sync_inodes_sb(sb);
 34         else
 35                 writeback_inodes_sb(sb, WB_REASON_SYNC);
 36 
 37         if (sb->s_op->sync_fs)
 38                 sb->s_op->sync_fs(sb, wait);
 39         return __sync_blockdev(sb->s_bdev, wait);
 40 }
 41 
 42 /*
 43  * Write out and wait upon all dirty data associated with this
 44  * superblock.  Filesystem data as well as the underlying block
 45  * device.  Takes the superblock lock.
 46  */
 47 int sync_filesystem(struct super_block *sb)
 48 {
 49         int ret;
 50 
 51         /*
 52          * We need to be protected against the filesystem going from
 53          * r/o to r/w or vice versa.
 54          */
 55         WARN_ON(!rwsem_is_locked(&sb->s_umount));
 56 
 57         /*
 58          * No point in syncing out anything if the filesystem is read-only.
 59          */
 60         if (sb->s_flags & MS_RDONLY)
 61                 return 0;
 62 
 63         ret = __sync_filesystem(sb, 0);
 64         if (ret < 0)
 65                 return ret;
 66         return __sync_filesystem(sb, 1);
 67 }
 68 EXPORT_SYMBOL_GPL(sync_filesystem);
 69 
 70 static void sync_inodes_one_sb(struct super_block *sb, void *arg)
 71 {
 72         if (!(sb->s_flags & MS_RDONLY))
 73                 sync_inodes_sb(sb);
 74 }
 75 
 76 static void sync_fs_one_sb(struct super_block *sb, void *arg)
 77 {
 78         if (!(sb->s_flags & MS_RDONLY) && sb->s_op->sync_fs)
 79                 sb->s_op->sync_fs(sb, *(int *)arg);
 80 }
 81 
 82 static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
 83 {
 84         filemap_fdatawrite(bdev->bd_inode->i_mapping);
 85 }
 86 
 87 static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
 88 {
 89         filemap_fdatawait(bdev->bd_inode->i_mapping);
 90 }
 91 
 92 /*
 93  * Sync everything. We start by waking flusher threads so that most of
 94  * writeback runs on all devices in parallel. Then we sync all inodes reliably
 95  * which effectively also waits for all flusher threads to finish doing
 96  * writeback. At this point all data is on disk so metadata should be stable
 97  * and we tell filesystems to sync their metadata via ->sync_fs() calls.
 98  * Finally, we writeout all block devices because some filesystems (e.g. ext2)
 99  * just write metadata (such as inodes or bitmaps) to block device page cache
100  * and do not sync it on their own in ->sync_fs().
101  */
102 SYSCALL_DEFINE0(sync)
103 {
104         int nowait = 0, wait = 1;
105 
106         wakeup_flusher_threads(0, WB_REASON_SYNC);
107         iterate_supers(sync_inodes_one_sb, NULL);
108         iterate_supers(sync_fs_one_sb, &nowait);
109         iterate_supers(sync_fs_one_sb, &wait);
110         iterate_bdevs(fdatawrite_one_bdev, NULL);
111         iterate_bdevs(fdatawait_one_bdev, NULL);
112         if (unlikely(laptop_mode))
113                 laptop_sync_completion();
114         return 0;
115 }
116 
117 static void do_sync_work(struct work_struct *work)
118 {
119         int nowait = 0;
120 
121         /*
122          * Sync twice to reduce the possibility we skipped some inodes / pages
123          * because they were temporarily locked
124          */
125         iterate_supers(sync_inodes_one_sb, &nowait);
126         iterate_supers(sync_fs_one_sb, &nowait);
127         iterate_bdevs(fdatawrite_one_bdev, NULL);
128         iterate_supers(sync_inodes_one_sb, &nowait);
129         iterate_supers(sync_fs_one_sb, &nowait);
130         iterate_bdevs(fdatawrite_one_bdev, NULL);
131         printk("Emergency Sync complete\n");
132         kfree(work);
133 }
134 
135 void emergency_sync(void)
136 {
137         struct work_struct *work;
138 
139         work = kmalloc(sizeof(*work), GFP_ATOMIC);
140         if (work) {
141                 INIT_WORK(work, do_sync_work);
142                 schedule_work(work);
143         }
144 }
145 
146 /*
147  * sync a single super
148  */
149 SYSCALL_DEFINE1(syncfs, int, fd)
150 {
151         struct fd f = fdget(fd);
152         struct super_block *sb;
153         int ret;
154 
155         if (!f.file)
156                 return -EBADF;
157         sb = f.file->f_dentry->d_sb;
158 
159         down_read(&sb->s_umount);
160         ret = sync_filesystem(sb);
161         up_read(&sb->s_umount);
162 
163         fdput(f);
164         return ret;
165 }
166 
167 /**
168  * vfs_fsync_range - helper to sync a range of data & metadata to disk
169  * @file:               file to sync
170  * @start:              offset in bytes of the beginning of data range to sync
171  * @end:                offset in bytes of the end of data range (inclusive)
172  * @datasync:           perform only datasync
173  *
174  * Write back data in range @start..@end and metadata for @file to disk.  If
175  * @datasync is set only metadata needed to access modified file data is
176  * written.
177  */
178 int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
179 {
180         if (!file->f_op || !file->f_op->fsync)
181                 return -EINVAL;
182         return file->f_op->fsync(file, start, end, datasync);
183 }
184 EXPORT_SYMBOL(vfs_fsync_range);
185 
186 /**
187  * vfs_fsync - perform a fsync or fdatasync on a file
188  * @file:               file to sync
189  * @datasync:           only perform a fdatasync operation
190  *
191  * Write back data and metadata for @file to disk.  If @datasync is
192  * set only metadata needed to access modified file data is written.
193  */
194 int vfs_fsync(struct file *file, int datasync)
195 {
196         return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
197 }
198 EXPORT_SYMBOL(vfs_fsync);
199 
200 static int do_fsync(unsigned int fd, int datasync)
201 {
202         struct fd f = fdget(fd);
203         int ret = -EBADF;
204 
205         if (f.file) {
206                 ret = vfs_fsync(f.file, datasync);
207                 fdput(f);
208         }
209         return ret;
210 }
211 
212 SYSCALL_DEFINE1(fsync, unsigned int, fd)
213 {
214         return do_fsync(fd, 0);
215 }
216 
217 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
218 {
219         return do_fsync(fd, 1);
220 }
221 
222 /*
223  * sys_sync_file_range() permits finely controlled syncing over a segment of
224  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
225  * zero then sys_sync_file_range() will operate from offset out to EOF.
226  *
227  * The flag bits are:
228  *
229  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
230  * before performing the write.
231  *
232  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
233  * range which are not presently under writeback. Note that this may block for
234  * significant periods due to exhaustion of disk request structures.
235  *
236  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
237  * after performing the write.
238  *
239  * Useful combinations of the flag bits are:
240  *
241  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
242  * in the range which were dirty on entry to sys_sync_file_range() are placed
243  * under writeout.  This is a start-write-for-data-integrity operation.
244  *
245  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
246  * are not presently under writeout.  This is an asynchronous flush-to-disk
247  * operation.  Not suitable for data integrity operations.
248  *
249  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
250  * completion of writeout of all pages in the range.  This will be used after an
251  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
252  * for that operation to complete and to return the result.
253  *
254  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
255  * a traditional sync() operation.  This is a write-for-data-integrity operation
256  * which will ensure that all pages in the range which were dirty on entry to
257  * sys_sync_file_range() are committed to disk.
258  *
259  *
260  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
261  * I/O errors or ENOSPC conditions and will return those to the caller, after
262  * clearing the EIO and ENOSPC flags in the address_space.
263  *
264  * It should be noted that none of these operations write out the file's
265  * metadata.  So unless the application is strictly performing overwrites of
266  * already-instantiated disk blocks, there are no guarantees here that the data
267  * will be available after a crash.
268  */
269 SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
270                                 unsigned int, flags)
271 {
272         int ret;
273         struct fd f;
274         struct address_space *mapping;
275         loff_t endbyte;                 /* inclusive */
276         umode_t i_mode;
277 
278         ret = -EINVAL;
279         if (flags & ~VALID_FLAGS)
280                 goto out;
281 
282         endbyte = offset + nbytes;
283 
284         if ((s64)offset < 0)
285                 goto out;
286         if ((s64)endbyte < 0)
287                 goto out;
288         if (endbyte < offset)
289                 goto out;
290 
291         if (sizeof(pgoff_t) == 4) {
292                 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
293                         /*
294                          * The range starts outside a 32 bit machine's
295                          * pagecache addressing capabilities.  Let it "succeed"
296                          */
297                         ret = 0;
298                         goto out;
299                 }
300                 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
301                         /*
302                          * Out to EOF
303                          */
304                         nbytes = 0;
305                 }
306         }
307 
308         if (nbytes == 0)
309                 endbyte = LLONG_MAX;
310         else
311                 endbyte--;              /* inclusive */
312 
313         ret = -EBADF;
314         f = fdget(fd);
315         if (!f.file)
316                 goto out;
317 
318         i_mode = file_inode(f.file)->i_mode;
319         ret = -ESPIPE;
320         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
321                         !S_ISLNK(i_mode))
322                 goto out_put;
323 
324         mapping = f.file->f_mapping;
325         if (!mapping) {
326                 ret = -EINVAL;
327                 goto out_put;
328         }
329 
330         ret = 0;
331         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
332                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
333                 if (ret < 0)
334                         goto out_put;
335         }
336 
337         if (flags & SYNC_FILE_RANGE_WRITE) {
338                 ret = filemap_fdatawrite_range(mapping, offset, endbyte);
339                 if (ret < 0)
340                         goto out_put;
341         }
342 
343         if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
344                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
345 
346 out_put:
347         fdput(f);
348 out:
349         return ret;
350 }
351 
352 /* It would be nice if people remember that not all the world's an i386
353    when they introduce new system calls */
354 SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
355                                  loff_t, offset, loff_t, nbytes)
356 {
357         return sys_sync_file_range(fd, offset, nbytes, flags);
358 }
359 

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