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v5.4
  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 */
 31static 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 */
 48int 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}
 69EXPORT_SYMBOL(sync_filesystem);
 70
 71static void sync_inodes_one_sb(struct super_block *sb, void *arg)
 72{
 73	if (!sb_rdonly(sb))
 74		sync_inodes_sb(sb);
 75}
 76
 77static 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
 83static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
 84{
 85	filemap_fdatawrite(bdev->bd_inode->i_mapping);
 86}
 87
 88static 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 */
108void 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
122SYSCALL_DEFINE0(sync)
123{
124	ksys_sync();
125	return 0;
126}
127
128static 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
146void 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 */
160SYSCALL_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 */
189int 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}
199EXPORT_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 */
209int vfs_fsync(struct file *file, int datasync)
210{
211	return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
212}
213EXPORT_SYMBOL(vfs_fsync);
214
215static 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
227SYSCALL_DEFINE1(fsync, unsigned int, fd)
228{
229	return do_fsync(fd, 0);
230}
231
232SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
233{
234	return do_fsync(fd, 1);
235}
236
237int 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
310out:
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 */
364int 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
379SYSCALL_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 */
387SYSCALL_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}
v6.8
  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * High-level sync()-related operations
  4 */
  5
  6#include <linux/blkdev.h>
  7#include <linux/kernel.h>
  8#include <linux/file.h>
  9#include <linux/fs.h>
 10#include <linux/slab.h>
 11#include <linux/export.h>
 12#include <linux/namei.h>
 13#include <linux/sched.h>
 14#include <linux/writeback.h>
 15#include <linux/syscalls.h>
 16#include <linux/linkage.h>
 17#include <linux/pagemap.h>
 18#include <linux/quotaops.h>
 19#include <linux/backing-dev.h>
 20#include "internal.h"
 21
 22#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
 23			SYNC_FILE_RANGE_WAIT_AFTER)
 24
 25/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 26 * Write out and wait upon all dirty data associated with this
 27 * superblock.  Filesystem data as well as the underlying block
 28 * device.  Takes the superblock lock.
 29 */
 30int sync_filesystem(struct super_block *sb)
 31{
 32	int ret = 0;
 33
 34	/*
 35	 * We need to be protected against the filesystem going from
 36	 * r/o to r/w or vice versa.
 37	 */
 38	WARN_ON(!rwsem_is_locked(&sb->s_umount));
 39
 40	/*
 41	 * No point in syncing out anything if the filesystem is read-only.
 42	 */
 43	if (sb_rdonly(sb))
 44		return 0;
 45
 46	/*
 47	 * Do the filesystem syncing work.  For simple filesystems
 48	 * writeback_inodes_sb(sb) just dirties buffers with inodes so we have
 49	 * to submit I/O for these buffers via sync_blockdev().  This also
 50	 * speeds up the wait == 1 case since in that case write_inode()
 51	 * methods call sync_dirty_buffer() and thus effectively write one block
 52	 * at a time.
 53	 */
 54	writeback_inodes_sb(sb, WB_REASON_SYNC);
 55	if (sb->s_op->sync_fs) {
 56		ret = sb->s_op->sync_fs(sb, 0);
 57		if (ret)
 58			return ret;
 59	}
 60	ret = sync_blockdev_nowait(sb->s_bdev);
 61	if (ret)
 62		return ret;
 63
 64	sync_inodes_sb(sb);
 65	if (sb->s_op->sync_fs) {
 66		ret = sb->s_op->sync_fs(sb, 1);
 67		if (ret)
 68			return ret;
 69	}
 70	return sync_blockdev(sb->s_bdev);
 71}
 72EXPORT_SYMBOL(sync_filesystem);
 73
 74static void sync_inodes_one_sb(struct super_block *sb, void *arg)
 75{
 76	if (!sb_rdonly(sb))
 77		sync_inodes_sb(sb);
 78}
 79
 80static void sync_fs_one_sb(struct super_block *sb, void *arg)
 81{
 82	if (!sb_rdonly(sb) && !(sb->s_iflags & SB_I_SKIP_SYNC) &&
 83	    sb->s_op->sync_fs)
 84		sb->s_op->sync_fs(sb, *(int *)arg);
 85}
 86
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 87/*
 88 * Sync everything. We start by waking flusher threads so that most of
 89 * writeback runs on all devices in parallel. Then we sync all inodes reliably
 90 * which effectively also waits for all flusher threads to finish doing
 91 * writeback. At this point all data is on disk so metadata should be stable
 92 * and we tell filesystems to sync their metadata via ->sync_fs() calls.
 93 * Finally, we writeout all block devices because some filesystems (e.g. ext2)
 94 * just write metadata (such as inodes or bitmaps) to block device page cache
 95 * and do not sync it on their own in ->sync_fs().
 96 */
 97void ksys_sync(void)
 98{
 99	int nowait = 0, wait = 1;
100
101	wakeup_flusher_threads(WB_REASON_SYNC);
102	iterate_supers(sync_inodes_one_sb, NULL);
103	iterate_supers(sync_fs_one_sb, &nowait);
104	iterate_supers(sync_fs_one_sb, &wait);
105	sync_bdevs(false);
106	sync_bdevs(true);
107	if (unlikely(laptop_mode))
108		laptop_sync_completion();
109}
110
111SYSCALL_DEFINE0(sync)
112{
113	ksys_sync();
114	return 0;
115}
116
117static 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	sync_bdevs(false);
128	iterate_supers(sync_inodes_one_sb, &nowait);
129	iterate_supers(sync_fs_one_sb, &nowait);
130	sync_bdevs(false);
131	printk("Emergency Sync complete\n");
132	kfree(work);
133}
134
135void 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 */
149SYSCALL_DEFINE1(syncfs, int, fd)
150{
151	struct fd f = fdget(fd);
152	struct super_block *sb;
153	int ret, ret2;
154
155	if (!f.file)
156		return -EBADF;
157	sb = f.file->f_path.dentry->d_sb;
158
159	down_read(&sb->s_umount);
160	ret = sync_filesystem(sb);
161	up_read(&sb->s_umount);
162
163	ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
164
165	fdput(f);
166	return ret ? ret : ret2;
167}
168
169/**
170 * vfs_fsync_range - helper to sync a range of data & metadata to disk
171 * @file:		file to sync
172 * @start:		offset in bytes of the beginning of data range to sync
173 * @end:		offset in bytes of the end of data range (inclusive)
174 * @datasync:		perform only datasync
175 *
176 * Write back data in range @start..@end and metadata for @file to disk.  If
177 * @datasync is set only metadata needed to access modified file data is
178 * written.
179 */
180int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
181{
182	struct inode *inode = file->f_mapping->host;
183
184	if (!file->f_op->fsync)
185		return -EINVAL;
186	if (!datasync && (inode->i_state & I_DIRTY_TIME))
187		mark_inode_dirty_sync(inode);
188	return file->f_op->fsync(file, start, end, datasync);
189}
190EXPORT_SYMBOL(vfs_fsync_range);
191
192/**
193 * vfs_fsync - perform a fsync or fdatasync on a file
194 * @file:		file to sync
195 * @datasync:		only perform a fdatasync operation
196 *
197 * Write back data and metadata for @file to disk.  If @datasync is
198 * set only metadata needed to access modified file data is written.
199 */
200int vfs_fsync(struct file *file, int datasync)
201{
202	return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
203}
204EXPORT_SYMBOL(vfs_fsync);
205
206static int do_fsync(unsigned int fd, int datasync)
207{
208	struct fd f = fdget(fd);
209	int ret = -EBADF;
210
211	if (f.file) {
212		ret = vfs_fsync(f.file, datasync);
213		fdput(f);
214	}
215	return ret;
216}
217
218SYSCALL_DEFINE1(fsync, unsigned int, fd)
219{
220	return do_fsync(fd, 0);
221}
222
223SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
224{
225	return do_fsync(fd, 1);
226}
227
228int sync_file_range(struct file *file, loff_t offset, loff_t nbytes,
229		    unsigned int flags)
230{
231	int ret;
232	struct address_space *mapping;
233	loff_t endbyte;			/* inclusive */
234	umode_t i_mode;
235
236	ret = -EINVAL;
237	if (flags & ~VALID_FLAGS)
238		goto out;
239
240	endbyte = offset + nbytes;
241
242	if ((s64)offset < 0)
243		goto out;
244	if ((s64)endbyte < 0)
245		goto out;
246	if (endbyte < offset)
247		goto out;
248
249	if (sizeof(pgoff_t) == 4) {
250		if (offset >= (0x100000000ULL << PAGE_SHIFT)) {
251			/*
252			 * The range starts outside a 32 bit machine's
253			 * pagecache addressing capabilities.  Let it "succeed"
254			 */
255			ret = 0;
256			goto out;
257		}
258		if (endbyte >= (0x100000000ULL << PAGE_SHIFT)) {
259			/*
260			 * Out to EOF
261			 */
262			nbytes = 0;
263		}
264	}
265
266	if (nbytes == 0)
267		endbyte = LLONG_MAX;
268	else
269		endbyte--;		/* inclusive */
270
271	i_mode = file_inode(file)->i_mode;
272	ret = -ESPIPE;
273	if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
274			!S_ISLNK(i_mode))
275		goto out;
276
277	mapping = file->f_mapping;
278	ret = 0;
279	if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
280		ret = file_fdatawait_range(file, offset, endbyte);
281		if (ret < 0)
282			goto out;
283	}
284
285	if (flags & SYNC_FILE_RANGE_WRITE) {
286		int sync_mode = WB_SYNC_NONE;
287
288		if ((flags & SYNC_FILE_RANGE_WRITE_AND_WAIT) ==
289			     SYNC_FILE_RANGE_WRITE_AND_WAIT)
290			sync_mode = WB_SYNC_ALL;
291
292		ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
293						 sync_mode);
294		if (ret < 0)
295			goto out;
296	}
297
298	if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
299		ret = file_fdatawait_range(file, offset, endbyte);
300
301out:
302	return ret;
303}
304
305/*
306 * ksys_sync_file_range() permits finely controlled syncing over a segment of
307 * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
308 * zero then ksys_sync_file_range() will operate from offset out to EOF.
309 *
310 * The flag bits are:
311 *
312 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
313 * before performing the write.
314 *
315 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
316 * range which are not presently under writeback. Note that this may block for
317 * significant periods due to exhaustion of disk request structures.
318 *
319 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
320 * after performing the write.
321 *
322 * Useful combinations of the flag bits are:
323 *
324 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
325 * in the range which were dirty on entry to ksys_sync_file_range() are placed
326 * under writeout.  This is a start-write-for-data-integrity operation.
327 *
328 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
329 * are not presently under writeout.  This is an asynchronous flush-to-disk
330 * operation.  Not suitable for data integrity operations.
331 *
332 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
333 * completion of writeout of all pages in the range.  This will be used after an
334 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
335 * for that operation to complete and to return the result.
336 *
337 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER
338 * (a.k.a. SYNC_FILE_RANGE_WRITE_AND_WAIT):
339 * a traditional sync() operation.  This is a write-for-data-integrity operation
340 * which will ensure that all pages in the range which were dirty on entry to
341 * ksys_sync_file_range() are written to disk.  It should be noted that disk
342 * caches are not flushed by this call, so there are no guarantees here that the
343 * data will be available on disk after a crash.
344 *
345 *
346 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
347 * I/O errors or ENOSPC conditions and will return those to the caller, after
348 * clearing the EIO and ENOSPC flags in the address_space.
349 *
350 * It should be noted that none of these operations write out the file's
351 * metadata.  So unless the application is strictly performing overwrites of
352 * already-instantiated disk blocks, there are no guarantees here that the data
353 * will be available after a crash.
354 */
355int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
356			 unsigned int flags)
357{
358	int ret;
359	struct fd f;
360
361	ret = -EBADF;
362	f = fdget(fd);
363	if (f.file)
364		ret = sync_file_range(f.file, offset, nbytes, flags);
365
366	fdput(f);
367	return ret;
368}
369
370SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
371				unsigned int, flags)
372{
373	return ksys_sync_file_range(fd, offset, nbytes, flags);
374}
375
376#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_SYNC_FILE_RANGE)
377COMPAT_SYSCALL_DEFINE6(sync_file_range, int, fd, compat_arg_u64_dual(offset),
378		       compat_arg_u64_dual(nbytes), unsigned int, flags)
379{
380	return ksys_sync_file_range(fd, compat_arg_u64_glue(offset),
381				    compat_arg_u64_glue(nbytes), flags);
382}
383#endif
384
385/* It would be nice if people remember that not all the world's an i386
386   when they introduce new system calls */
387SYSCALL_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}