projects/linux·blob v3.2 · refs

383 lines · 9.9 KiB

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/module.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/buffer_head.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 /*
34 * This should be safe, as we require bdi backing to actually
35 * write out data in the first place
36 */
37 if (sb->s_bdi == &noop_backing_dev_info)
38 return 0;
39
40 if (sb->s_qcop && sb->s_qcop->quota_sync)
41 sb->s_qcop->quota_sync(sb, -1, wait);
42
43 if (wait)
44 sync_inodes_sb(sb);
45 else
46 writeback_inodes_sb(sb, WB_REASON_SYNC);
47
48 if (sb->s_op->sync_fs)
49 sb->s_op->sync_fs(sb, wait);
50 return __sync_blockdev(sb->s_bdev, wait);
51}
52
53/*
54 * Write out and wait upon all dirty data associated with this
55 * superblock. Filesystem data as well as the underlying block
56 * device. Takes the superblock lock.
57 */
58int sync_filesystem(struct super_block *sb)
59{
60 int ret;
61
62 /*
63 * We need to be protected against the filesystem going from
64 * r/o to r/w or vice versa.
65 */
66 WARN_ON(!rwsem_is_locked(&sb->s_umount));
67
68 /*
69 * No point in syncing out anything if the filesystem is read-only.
70 */
71 if (sb->s_flags & MS_RDONLY)
72 return 0;
73
74 ret = __sync_filesystem(sb, 0);
75 if (ret < 0)
76 return ret;
77 return __sync_filesystem(sb, 1);
78}
79EXPORT_SYMBOL_GPL(sync_filesystem);
80
81static void sync_one_sb(struct super_block *sb, void *arg)
82{
83 if (!(sb->s_flags & MS_RDONLY))
84 __sync_filesystem(sb, *(int *)arg);
85}
86/*
87 * Sync all the data for all the filesystems (called by sys_sync() and
88 * emergency sync)
89 */
90static void sync_filesystems(int wait)
91{
92 iterate_supers(sync_one_sb, &wait);
93}
94
95/*
96 * sync everything. Start out by waking pdflush, because that writes back
97 * all queues in parallel.
98 */
99SYSCALL_DEFINE0(sync)
100{
101 wakeup_flusher_threads(0, WB_REASON_SYNC);
102 sync_filesystems(0);
103 sync_filesystems(1);
104 if (unlikely(laptop_mode))
105 laptop_sync_completion();
106 return 0;
107}
108
109static void do_sync_work(struct work_struct *work)
110{
111 /*
112 * Sync twice to reduce the possibility we skipped some inodes / pages
113 * because they were temporarily locked
114 */
115 sync_filesystems(0);
116 sync_filesystems(0);
117 printk("Emergency Sync complete\n");
118 kfree(work);
119}
120
121void emergency_sync(void)
122{
123 struct work_struct *work;
124
125 work = kmalloc(sizeof(*work), GFP_ATOMIC);
126 if (work) {
127 INIT_WORK(work, do_sync_work);
128 schedule_work(work);
129 }
130}
131
132/*
133 * sync a single super
134 */
135SYSCALL_DEFINE1(syncfs, int, fd)
136{
137 struct file *file;
138 struct super_block *sb;
139 int ret;
140 int fput_needed;
141
142 file = fget_light(fd, &fput_needed);
143 if (!file)
144 return -EBADF;
145 sb = file->f_dentry->d_sb;
146
147 down_read(&sb->s_umount);
148 ret = sync_filesystem(sb);
149 up_read(&sb->s_umount);
150
151 fput_light(file, fput_needed);
152 return ret;
153}
154
155/**
156 * vfs_fsync_range - helper to sync a range of data & metadata to disk
157 * @file: file to sync
158 * @start: offset in bytes of the beginning of data range to sync
159 * @end: offset in bytes of the end of data range (inclusive)
160 * @datasync: perform only datasync
161 *
162 * Write back data in range @start..@end and metadata for @file to disk. If
163 * @datasync is set only metadata needed to access modified file data is
164 * written.
165 */
166int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
167{
168 if (!file->f_op || !file->f_op->fsync)
169 return -EINVAL;
170 return file->f_op->fsync(file, start, end, datasync);
171}
172EXPORT_SYMBOL(vfs_fsync_range);
173
174/**
175 * vfs_fsync - perform a fsync or fdatasync on a file
176 * @file: file to sync
177 * @datasync: only perform a fdatasync operation
178 *
179 * Write back data and metadata for @file to disk. If @datasync is
180 * set only metadata needed to access modified file data is written.
181 */
182int vfs_fsync(struct file *file, int datasync)
183{
184 return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
185}
186EXPORT_SYMBOL(vfs_fsync);
187
188static int do_fsync(unsigned int fd, int datasync)
189{
190 struct file *file;
191 int ret = -EBADF;
192
193 file = fget(fd);
194 if (file) {
195 ret = vfs_fsync(file, datasync);
196 fput(file);
197 }
198 return ret;
199}
200
201SYSCALL_DEFINE1(fsync, unsigned int, fd)
202{
203 return do_fsync(fd, 0);
204}
205
206SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
207{
208 return do_fsync(fd, 1);
209}
210
211/**
212 * generic_write_sync - perform syncing after a write if file / inode is sync
213 * @file: file to which the write happened
214 * @pos: offset where the write started
215 * @count: length of the write
216 *
217 * This is just a simple wrapper about our general syncing function.
218 */
219int generic_write_sync(struct file *file, loff_t pos, loff_t count)
220{
221 if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
222 return 0;
223 return vfs_fsync_range(file, pos, pos + count - 1,
224 (file->f_flags & __O_SYNC) ? 0 : 1);
225}
226EXPORT_SYMBOL(generic_write_sync);
227
228/*
229 * sys_sync_file_range() permits finely controlled syncing over a segment of
230 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
231 * zero then sys_sync_file_range() will operate from offset out to EOF.
232 *
233 * The flag bits are:
234 *
235 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
236 * before performing the write.
237 *
238 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
239 * range which are not presently under writeback. Note that this may block for
240 * significant periods due to exhaustion of disk request structures.
241 *
242 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
243 * after performing the write.
244 *
245 * Useful combinations of the flag bits are:
246 *
247 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
248 * in the range which were dirty on entry to sys_sync_file_range() are placed
249 * under writeout. This is a start-write-for-data-integrity operation.
250 *
251 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
252 * are not presently under writeout. This is an asynchronous flush-to-disk
253 * operation. Not suitable for data integrity operations.
254 *
255 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
256 * completion of writeout of all pages in the range. This will be used after an
257 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
258 * for that operation to complete and to return the result.
259 *
260 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
261 * a traditional sync() operation. This is a write-for-data-integrity operation
262 * which will ensure that all pages in the range which were dirty on entry to
263 * sys_sync_file_range() are committed to disk.
264 *
265 *
266 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
267 * I/O errors or ENOSPC conditions and will return those to the caller, after
268 * clearing the EIO and ENOSPC flags in the address_space.
269 *
270 * It should be noted that none of these operations write out the file's
271 * metadata. So unless the application is strictly performing overwrites of
272 * already-instantiated disk blocks, there are no guarantees here that the data
273 * will be available after a crash.
274 */
275SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
276 unsigned int flags)
277{
278 int ret;
279 struct file *file;
280 struct address_space *mapping;
281 loff_t endbyte; /* inclusive */
282 int fput_needed;
283 umode_t i_mode;
284
285 ret = -EINVAL;
286 if (flags & ~VALID_FLAGS)
287 goto out;
288
289 endbyte = offset + nbytes;
290
291 if ((s64)offset < 0)
292 goto out;
293 if ((s64)endbyte < 0)
294 goto out;
295 if (endbyte < offset)
296 goto out;
297
298 if (sizeof(pgoff_t) == 4) {
299 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
300 /*
301 * The range starts outside a 32 bit machine's
302 * pagecache addressing capabilities. Let it "succeed"
303 */
304 ret = 0;
305 goto out;
306 }
307 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
308 /*
309 * Out to EOF
310 */
311 nbytes = 0;
312 }
313 }
314
315 if (nbytes == 0)
316 endbyte = LLONG_MAX;
317 else
318 endbyte--; /* inclusive */
319
320 ret = -EBADF;
321 file = fget_light(fd, &fput_needed);
322 if (!file)
323 goto out;
324
325 i_mode = file->f_path.dentry->d_inode->i_mode;
326 ret = -ESPIPE;
327 if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
328 !S_ISLNK(i_mode))
329 goto out_put;
330
331 mapping = file->f_mapping;
332 if (!mapping) {
333 ret = -EINVAL;
334 goto out_put;
335 }
336
337 ret = 0;
338 if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
339 ret = filemap_fdatawait_range(mapping, offset, endbyte);
340 if (ret < 0)
341 goto out_put;
342 }
343
344 if (flags & SYNC_FILE_RANGE_WRITE) {
345 ret = filemap_fdatawrite_range(mapping, offset, endbyte);
346 if (ret < 0)
347 goto out_put;
348 }
349
350 if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
351 ret = filemap_fdatawait_range(mapping, offset, endbyte);
352
353out_put:
354 fput_light(file, fput_needed);
355out:
356 return ret;
357}
358#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
359asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
360 long flags)
361{
362 return SYSC_sync_file_range((int) fd, offset, nbytes,
363 (unsigned int) flags);
364}
365SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
366#endif
367
368/* It would be nice if people remember that not all the world's an i386
369 when they introduce new system calls */
370SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
371 loff_t offset, loff_t nbytes)
372{
373 return sys_sync_file_range(fd, offset, nbytes, flags);
374}
375#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
376asmlinkage long SyS_sync_file_range2(long fd, long flags,
377 loff_t offset, loff_t nbytes)
378{
379 return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
380 offset, nbytes);
381}
382SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
383#endif