1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * High-level sync()-related operations
4 */
5
6 #include <linux/kernel.h>
7 #include <linux/file.h>
8 #include <linux/fs.h>
9 #include <linux/slab.h>
10 #include <linux/export.h>
11 #include <linux/namei.h>
12 #include <linux/sched.h>
13 #include <linux/writeback.h>
14 #include <linux/syscalls.h>
15 #include <linux/linkage.h>
16 #include <linux/pagemap.h>
17 #include <linux/quotaops.h>
18 #include <linux/backing-dev.h>
19 #include "internal.h"
20
21 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
22 SYNC_FILE_RANGE_WAIT_AFTER)
23
24 /*
25 * Do the filesystem syncing work. For simple filesystems
26 * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
27 * submit IO for these buffers via __sync_blockdev(). This also speeds up the
28 * wait == 1 case since in that case write_inode() functions do
29 * sync_dirty_buffer() and thus effectively write one block at a time.
30 */
31 static int __sync_filesystem(struct super_block *sb, int wait)
32 {
33 if (wait)
34 sync_inodes_sb(sb);
35 else
36 writeback_inodes_sb(sb, WB_REASON_SYNC);
37
38 if (sb->s_op->sync_fs)
39 sb->s_op->sync_fs(sb, wait);
40 return __sync_blockdev(sb->s_bdev, wait);
41 }
42
43 /*
44 * Write out and wait upon all dirty data associated with this
45 * superblock. Filesystem data as well as the underlying block
46 * device. Takes the superblock lock.
47 */
48 int sync_filesystem(struct super_block *sb)
49 {
50 int ret;
51
52 /*
53 * We need to be protected against the filesystem going from
54 * r/o to r/w or vice versa.
55 */
56 WARN_ON(!rwsem_is_locked(&sb->s_umount));
57
58 /*
59 * No point in syncing out anything if the filesystem is read-only.
60 */
61 if (sb_rdonly(sb))
62 return 0;
63
64 ret = __sync_filesystem(sb, 0);
65 if (ret < 0)
66 return ret;
67 return __sync_filesystem(sb, 1);
68 }
69 EXPORT_SYMBOL(sync_filesystem);
70
71 static void sync_inodes_one_sb(struct super_block *sb, void *arg)
72 {
73 if (!sb_rdonly(sb))
74 sync_inodes_sb(sb);
75 }
76
77 static void sync_fs_one_sb(struct super_block *sb, void *arg)
78 {
79 if (!sb_rdonly(sb) && sb->s_op->sync_fs)
80 sb->s_op->sync_fs(sb, *(int *)arg);
81 }
82
83 static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
84 {
85 filemap_fdatawrite(bdev->bd_inode->i_mapping);
86 }
87
88 static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
89 {
90 /*
91 * We keep the error status of individual mapping so that
92 * applications can catch the writeback error using fsync(2).
93 * See filemap_fdatawait_keep_errors() for details.
94 */
95 filemap_fdatawait_keep_errors(bdev->bd_inode->i_mapping);
96 }
97
98 /*
99 * Sync everything. We start by waking flusher threads so that most of
100 * writeback runs on all devices in parallel. Then we sync all inodes reliably
101 * which effectively also waits for all flusher threads to finish doing
102 * writeback. At this point all data is on disk so metadata should be stable
103 * and we tell filesystems to sync their metadata via ->sync_fs() calls.
104 * Finally, we writeout all block devices because some filesystems (e.g. ext2)
105 * just write metadata (such as inodes or bitmaps) to block device page cache
106 * and do not sync it on their own in ->sync_fs().
107 */
108 void ksys_sync(void)
109 {
110 int nowait = 0, wait = 1;
111
112 wakeup_flusher_threads(WB_REASON_SYNC);
113 iterate_supers(sync_inodes_one_sb, NULL);
114 iterate_supers(sync_fs_one_sb, &nowait);
115 iterate_supers(sync_fs_one_sb, &wait);
116 iterate_bdevs(fdatawrite_one_bdev, NULL);
117 iterate_bdevs(fdatawait_one_bdev, NULL);
118 if (unlikely(laptop_mode))
119 laptop_sync_completion();
120 }
121
122 SYSCALL_DEFINE0(sync)
123 {
124 ksys_sync();
125 return 0;
126 }
127
128 static void do_sync_work(struct work_struct *work)
129 {
130 int nowait = 0;
131
132 /*
133 * Sync twice to reduce the possibility we skipped some inodes / pages
134 * because they were temporarily locked
135 */
136 iterate_supers(sync_inodes_one_sb, &nowait);
137 iterate_supers(sync_fs_one_sb, &nowait);
138 iterate_bdevs(fdatawrite_one_bdev, NULL);
139 iterate_supers(sync_inodes_one_sb, &nowait);
140 iterate_supers(sync_fs_one_sb, &nowait);
141 iterate_bdevs(fdatawrite_one_bdev, NULL);
142 printk("Emergency Sync complete\n");
143 kfree(work);
144 }
145
146 void emergency_sync(void)
147 {
148 struct work_struct *work;
149
150 work = kmalloc(sizeof(*work), GFP_ATOMIC);
151 if (work) {
152 INIT_WORK(work, do_sync_work);
153 schedule_work(work);
154 }
155 }
156
157 /*
158 * sync a single super
159 */
160 SYSCALL_DEFINE1(syncfs, int, fd)
161 {
162 struct fd f = fdget(fd);
163 struct super_block *sb;
164 int ret;
165
166 if (!f.file)
167 return -EBADF;
168 sb = f.file->f_path.dentry->d_sb;
169
170 down_read(&sb->s_umount);
171 ret = sync_filesystem(sb);
172 up_read(&sb->s_umount);
173
174 fdput(f);
175 return ret;
176 }
177
178 /**
179 * vfs_fsync_range - helper to sync a range of data & metadata to disk
180 * @file: file to sync
181 * @start: offset in bytes of the beginning of data range to sync
182 * @end: offset in bytes of the end of data range (inclusive)
183 * @datasync: perform only datasync
184 *
185 * Write back data in range @start..@end and metadata for @file to disk. If
186 * @datasync is set only metadata needed to access modified file data is
187 * written.
188 */
189 int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
190 {
191 struct inode *inode = file->f_mapping->host;
192
193 if (!file->f_op->fsync)
194 return -EINVAL;
195 if (!datasync && (inode->i_state & I_DIRTY_TIME))
196 mark_inode_dirty_sync(inode);
197 return file->f_op->fsync(file, start, end, datasync);
198 }
199 EXPORT_SYMBOL(vfs_fsync_range);
200
201 /**
202 * vfs_fsync - perform a fsync or fdatasync on a file
203 * @file: file to sync
204 * @datasync: only perform a fdatasync operation
205 *
206 * Write back data and metadata for @file to disk. If @datasync is
207 * set only metadata needed to access modified file data is written.
208 */
209 int vfs_fsync(struct file *file, int datasync)
210 {
211 return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
212 }
213 EXPORT_SYMBOL(vfs_fsync);
214
215 static int do_fsync(unsigned int fd, int datasync)
216 {
217 struct fd f = fdget(fd);
218 int ret = -EBADF;
219
220 if (f.file) {
221 ret = vfs_fsync(f.file, datasync);
222 fdput(f);
223 }
224 return ret;
225 }
226
227 SYSCALL_DEFINE1(fsync, unsigned int, fd)
228 {
229 return do_fsync(fd, 0);
230 }
231
232 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
233 {
234 return do_fsync(fd, 1);
235 }
236
237 int sync_file_range(struct file *file, loff_t offset, loff_t nbytes,
238 unsigned int flags)
239 {
240 int ret;
241 struct address_space *mapping;
242 loff_t endbyte; /* inclusive */
243 umode_t i_mode;
244
245 ret = -EINVAL;
246 if (flags & ~VALID_FLAGS)
247 goto out;
248
249 endbyte = offset + nbytes;
250
251 if ((s64)offset < 0)
252 goto out;
253 if ((s64)endbyte < 0)
254 goto out;
255 if (endbyte < offset)
256 goto out;
257
258 if (sizeof(pgoff_t) == 4) {
259 if (offset >= (0x100000000ULL << PAGE_SHIFT)) {
260 /*
261 * The range starts outside a 32 bit machine's
262 * pagecache addressing capabilities. Let it "succeed"
263 */
264 ret = 0;
265 goto out;
266 }
267 if (endbyte >= (0x100000000ULL << PAGE_SHIFT)) {
268 /*
269 * Out to EOF
270 */
271 nbytes = 0;
272 }
273 }
274
275 if (nbytes == 0)
276 endbyte = LLONG_MAX;
277 else
278 endbyte--; /* inclusive */
279
280 i_mode = file_inode(file)->i_mode;
281 ret = -ESPIPE;
282 if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
283 !S_ISLNK(i_mode))
284 goto out;
285
286 mapping = file->f_mapping;
287 ret = 0;
288 if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
289 ret = file_fdatawait_range(file, offset, endbyte);
290 if (ret < 0)
291 goto out;
292 }
293
294 if (flags & SYNC_FILE_RANGE_WRITE) {
295 int sync_mode = WB_SYNC_NONE;
296
297 if ((flags & SYNC_FILE_RANGE_WRITE_AND_WAIT) ==
298 SYNC_FILE_RANGE_WRITE_AND_WAIT)
299 sync_mode = WB_SYNC_ALL;
300
301 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
302 sync_mode);
303 if (ret < 0)
304 goto out;
305 }
306
307 if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
308 ret = file_fdatawait_range(file, offset, endbyte);
309
310 out:
311 return ret;
312 }
313
314 /*
315 * ksys_sync_file_range() permits finely controlled syncing over a segment of
316 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
317 * zero then ksys_sync_file_range() will operate from offset out to EOF.
318 *
319 * The flag bits are:
320 *
321 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
322 * before performing the write.
323 *
324 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
325 * range which are not presently under writeback. Note that this may block for
326 * significant periods due to exhaustion of disk request structures.
327 *
328 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
329 * after performing the write.
330 *
331 * Useful combinations of the flag bits are:
332 *
333 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
334 * in the range which were dirty on entry to ksys_sync_file_range() are placed
335 * under writeout. This is a start-write-for-data-integrity operation.
336 *
337 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
338 * are not presently under writeout. This is an asynchronous flush-to-disk
339 * operation. Not suitable for data integrity operations.
340 *
341 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
342 * completion of writeout of all pages in the range. This will be used after an
343 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
344 * for that operation to complete and to return the result.
345 *
346 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER
347 * (a.k.a. SYNC_FILE_RANGE_WRITE_AND_WAIT):
348 * a traditional sync() operation. This is a write-for-data-integrity operation
349 * which will ensure that all pages in the range which were dirty on entry to
350 * ksys_sync_file_range() are written to disk. It should be noted that disk
351 * caches are not flushed by this call, so there are no guarantees here that the
352 * data will be available on disk after a crash.
353 *
354 *
355 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
356 * I/O errors or ENOSPC conditions and will return those to the caller, after
357 * clearing the EIO and ENOSPC flags in the address_space.
358 *
359 * It should be noted that none of these operations write out the file's
360 * metadata. So unless the application is strictly performing overwrites of
361 * already-instantiated disk blocks, there are no guarantees here that the data
362 * will be available after a crash.
363 */
364 int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
365 unsigned int flags)
366 {
367 int ret;
368 struct fd f;
369
370 ret = -EBADF;
371 f = fdget(fd);
372 if (f.file)
373 ret = sync_file_range(f.file, offset, nbytes, flags);
374
375 fdput(f);
376 return ret;
377 }
378
379 SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
380 unsigned int, flags)
381 {
382 return ksys_sync_file_range(fd, offset, nbytes, flags);
383 }
384
385 /* It would be nice if people remember that not all the world's an i386
386 when they introduce new system calls */
387 SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
388 loff_t, offset, loff_t, nbytes)
389 {
390 return ksys_sync_file_range(fd, offset, nbytes, flags);
391 }