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  */
__sync_filesystem(struct super_block * sb,int wait)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  */
sync_filesystem(struct super_block * sb)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 
sync_inodes_one_sb(struct super_block * sb,void * arg)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 
sync_fs_one_sb(struct super_block * sb,void * arg)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 
fdatawrite_one_bdev(struct block_device * bdev,void * arg)83 static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
84 {
85 	filemap_fdatawrite(bdev->bd_inode->i_mapping);
86 }
87 
fdatawait_one_bdev(struct block_device * bdev,void * arg)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  */
ksys_sync(void)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 
SYSCALL_DEFINE0(sync)122 SYSCALL_DEFINE0(sync)
123 {
124 	ksys_sync();
125 	return 0;
126 }
127 
do_sync_work(struct work_struct * work)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 
emergency_sync(void)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  */
SYSCALL_DEFINE1(syncfs,int,fd)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  */
vfs_fsync_range(struct file * file,loff_t start,loff_t end,int datasync)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  */
vfs_fsync(struct file * file,int datasync)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 
do_fsync(unsigned int fd,int datasync)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 
SYSCALL_DEFINE1(fsync,unsigned int,fd)227 SYSCALL_DEFINE1(fsync, unsigned int, fd)
228 {
229 	return do_fsync(fd, 0);
230 }
231 
SYSCALL_DEFINE1(fdatasync,unsigned int,fd)232 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
233 {
234 	return do_fsync(fd, 1);
235 }
236 
237 /*
238  * sys_sync_file_range() permits finely controlled syncing over a segment of
239  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
240  * zero then sys_sync_file_range() will operate from offset out to EOF.
241  *
242  * The flag bits are:
243  *
244  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
245  * before performing the write.
246  *
247  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
248  * range which are not presently under writeback. Note that this may block for
249  * significant periods due to exhaustion of disk request structures.
250  *
251  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
252  * after performing the write.
253  *
254  * Useful combinations of the flag bits are:
255  *
256  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
257  * in the range which were dirty on entry to sys_sync_file_range() are placed
258  * under writeout.  This is a start-write-for-data-integrity operation.
259  *
260  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
261  * are not presently under writeout.  This is an asynchronous flush-to-disk
262  * operation.  Not suitable for data integrity operations.
263  *
264  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
265  * completion of writeout of all pages in the range.  This will be used after an
266  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
267  * for that operation to complete and to return the result.
268  *
269  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
270  * a traditional sync() operation.  This is a write-for-data-integrity operation
271  * which will ensure that all pages in the range which were dirty on entry to
272  * sys_sync_file_range() are committed to disk.
273  *
274  *
275  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
276  * I/O errors or ENOSPC conditions and will return those to the caller, after
277  * clearing the EIO and ENOSPC flags in the address_space.
278  *
279  * It should be noted that none of these operations write out the file's
280  * metadata.  So unless the application is strictly performing overwrites of
281  * already-instantiated disk blocks, there are no guarantees here that the data
282  * will be available after a crash.
283  */
ksys_sync_file_range(int fd,loff_t offset,loff_t nbytes,unsigned int flags)284 int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
285 			 unsigned int flags)
286 {
287 	int ret;
288 	struct fd f;
289 	struct address_space *mapping;
290 	loff_t endbyte;			/* inclusive */
291 	umode_t i_mode;
292 
293 	ret = -EINVAL;
294 	if (flags & ~VALID_FLAGS)
295 		goto out;
296 
297 	endbyte = offset + nbytes;
298 
299 	if ((s64)offset < 0)
300 		goto out;
301 	if ((s64)endbyte < 0)
302 		goto out;
303 	if (endbyte < offset)
304 		goto out;
305 
306 	if (sizeof(pgoff_t) == 4) {
307 		if (offset >= (0x100000000ULL << PAGE_SHIFT)) {
308 			/*
309 			 * The range starts outside a 32 bit machine's
310 			 * pagecache addressing capabilities.  Let it "succeed"
311 			 */
312 			ret = 0;
313 			goto out;
314 		}
315 		if (endbyte >= (0x100000000ULL << PAGE_SHIFT)) {
316 			/*
317 			 * Out to EOF
318 			 */
319 			nbytes = 0;
320 		}
321 	}
322 
323 	if (nbytes == 0)
324 		endbyte = LLONG_MAX;
325 	else
326 		endbyte--;		/* inclusive */
327 
328 	ret = -EBADF;
329 	f = fdget(fd);
330 	if (!f.file)
331 		goto out;
332 
333 	i_mode = file_inode(f.file)->i_mode;
334 	ret = -ESPIPE;
335 	if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
336 			!S_ISLNK(i_mode))
337 		goto out_put;
338 
339 	mapping = f.file->f_mapping;
340 	ret = 0;
341 	if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
342 		ret = file_fdatawait_range(f.file, offset, endbyte);
343 		if (ret < 0)
344 			goto out_put;
345 	}
346 
347 	if (flags & SYNC_FILE_RANGE_WRITE) {
348 		ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
349 						 WB_SYNC_NONE);
350 		if (ret < 0)
351 			goto out_put;
352 	}
353 
354 	if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
355 		ret = file_fdatawait_range(f.file, offset, endbyte);
356 
357 out_put:
358 	fdput(f);
359 out:
360 	return ret;
361 }
362 
SYSCALL_DEFINE4(sync_file_range,int,fd,loff_t,offset,loff_t,nbytes,unsigned int,flags)363 SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
364 				unsigned int, flags)
365 {
366 	return ksys_sync_file_range(fd, offset, nbytes, flags);
367 }
368 
369 /* It would be nice if people remember that not all the world's an i386
370    when they introduce new system calls */
SYSCALL_DEFINE4(sync_file_range2,int,fd,unsigned int,flags,loff_t,offset,loff_t,nbytes)371 SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
372 				 loff_t, offset, loff_t, nbytes)
373 {
374 	return ksys_sync_file_range(fd, offset, nbytes, flags);
375 }
376