Root/fs/sync.c

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/sched.h>
11#include <linux/writeback.h>
12#include <linux/syscalls.h>
13#include <linux/linkage.h>
14#include <linux/pagemap.h>
15#include <linux/quotaops.h>
16#include <linux/buffer_head.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 */
30static int __sync_filesystem(struct super_block *sb, int wait)
31{
32    /*
33     * This should be safe, as we require bdi backing to actually
34     * write out data in the first place
35     */
36    if (!sb->s_bdi || sb->s_bdi == &noop_backing_dev_info)
37        return 0;
38
39    if (sb->s_qcop && sb->s_qcop->quota_sync)
40        sb->s_qcop->quota_sync(sb, -1, wait);
41
42    if (wait)
43        sync_inodes_sb(sb);
44    else
45        writeback_inodes_sb(sb);
46
47    if (sb->s_op->sync_fs)
48        sb->s_op->sync_fs(sb, wait);
49    return __sync_blockdev(sb->s_bdev, wait);
50}
51
52/*
53 * Write out and wait upon all dirty data associated with this
54 * superblock. Filesystem data as well as the underlying block
55 * device. Takes the superblock lock.
56 */
57int sync_filesystem(struct super_block *sb)
58{
59    int ret;
60
61    /*
62     * We need to be protected against the filesystem going from
63     * r/o to r/w or vice versa.
64     */
65    WARN_ON(!rwsem_is_locked(&sb->s_umount));
66
67    /*
68     * No point in syncing out anything if the filesystem is read-only.
69     */
70    if (sb->s_flags & MS_RDONLY)
71        return 0;
72
73    ret = __sync_filesystem(sb, 0);
74    if (ret < 0)
75        return ret;
76    return __sync_filesystem(sb, 1);
77}
78EXPORT_SYMBOL_GPL(sync_filesystem);
79
80/*
81 * Sync all the data for all the filesystems (called by sys_sync() and
82 * emergency sync)
83 *
84 * This operation is careful to avoid the livelock which could easily happen
85 * if two or more filesystems are being continuously dirtied. s_need_sync
86 * is used only here. We set it against all filesystems and then clear it as
87 * we sync them. So redirtied filesystems are skipped.
88 *
89 * But if process A is currently running sync_filesystems and then process B
90 * calls sync_filesystems as well, process B will set all the s_need_sync
91 * flags again, which will cause process A to resync everything. Fix that with
92 * a local mutex.
93 */
94static void sync_filesystems(int wait)
95{
96    struct super_block *sb;
97    static DEFINE_MUTEX(mutex);
98
99    mutex_lock(&mutex); /* Could be down_interruptible */
100    spin_lock(&sb_lock);
101    list_for_each_entry(sb, &super_blocks, s_list)
102        sb->s_need_sync = 1;
103
104restart:
105    list_for_each_entry(sb, &super_blocks, s_list) {
106        if (!sb->s_need_sync)
107            continue;
108        sb->s_need_sync = 0;
109        sb->s_count++;
110        spin_unlock(&sb_lock);
111
112        down_read(&sb->s_umount);
113        if (!(sb->s_flags & MS_RDONLY) && sb->s_root && sb->s_bdi)
114            __sync_filesystem(sb, wait);
115        up_read(&sb->s_umount);
116
117        /* restart only when sb is no longer on the list */
118        spin_lock(&sb_lock);
119        if (__put_super_and_need_restart(sb))
120            goto restart;
121    }
122    spin_unlock(&sb_lock);
123    mutex_unlock(&mutex);
124}
125
126/*
127 * sync everything. Start out by waking pdflush, because that writes back
128 * all queues in parallel.
129 */
130SYSCALL_DEFINE0(sync)
131{
132    wakeup_flusher_threads(0);
133    sync_filesystems(0);
134    sync_filesystems(1);
135    if (unlikely(laptop_mode))
136        laptop_sync_completion();
137    return 0;
138}
139
140static void do_sync_work(struct work_struct *work)
141{
142    /*
143     * Sync twice to reduce the possibility we skipped some inodes / pages
144     * because they were temporarily locked
145     */
146    sync_filesystems(0);
147    sync_filesystems(0);
148    printk("Emergency Sync complete\n");
149    kfree(work);
150}
151
152void emergency_sync(void)
153{
154    struct work_struct *work;
155
156    work = kmalloc(sizeof(*work), GFP_ATOMIC);
157    if (work) {
158        INIT_WORK(work, do_sync_work);
159        schedule_work(work);
160    }
161}
162
163/*
164 * Generic function to fsync a file.
165 *
166 * filp may be NULL if called via the msync of a vma.
167 */
168int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
169{
170    struct inode * inode = dentry->d_inode;
171    struct super_block * sb;
172    int ret, err;
173
174    /* sync the inode to buffers */
175    ret = write_inode_now(inode, 0);
176
177    /* sync the superblock to buffers */
178    sb = inode->i_sb;
179    if (sb->s_dirt && sb->s_op->write_super)
180        sb->s_op->write_super(sb);
181
182    /* .. finally sync the buffers to disk */
183    err = sync_blockdev(sb->s_bdev);
184    if (!ret)
185        ret = err;
186    return ret;
187}
188EXPORT_SYMBOL(file_fsync);
189
190/**
191 * vfs_fsync_range - helper to sync a range of data & metadata to disk
192 * @file: file to sync
193 * @dentry: dentry of @file
194 * @start: offset in bytes of the beginning of data range to sync
195 * @end: offset in bytes of the end of data range (inclusive)
196 * @datasync: perform only datasync
197 *
198 * Write back data in range @start..@end and metadata for @file to disk. If
199 * @datasync is set only metadata needed to access modified file data is
200 * written.
201 *
202 * In case this function is called from nfsd @file may be %NULL and
203 * only @dentry is set. This can only happen when the filesystem
204 * implements the export_operations API.
205 */
206int vfs_fsync_range(struct file *file, struct dentry *dentry, loff_t start,
207            loff_t end, int datasync)
208{
209    const struct file_operations *fop;
210    struct address_space *mapping;
211    int err, ret;
212
213    /*
214     * Get mapping and operations from the file in case we have
215     * as file, or get the default values for them in case we
216     * don't have a struct file available. Damn nfsd..
217     */
218    if (file) {
219        mapping = file->f_mapping;
220        fop = file->f_op;
221    } else {
222        mapping = dentry->d_inode->i_mapping;
223        fop = dentry->d_inode->i_fop;
224    }
225
226    if (!fop || !fop->fsync) {
227        ret = -EINVAL;
228        goto out;
229    }
230
231    ret = filemap_write_and_wait_range(mapping, start, end);
232
233    /*
234     * We need to protect against concurrent writers, which could cause
235     * livelocks in fsync_buffers_list().
236     */
237    mutex_lock(&mapping->host->i_mutex);
238    err = fop->fsync(file, dentry, datasync);
239    if (!ret)
240        ret = err;
241    mutex_unlock(&mapping->host->i_mutex);
242
243out:
244    return ret;
245}
246EXPORT_SYMBOL(vfs_fsync_range);
247
248/**
249 * vfs_fsync - perform a fsync or fdatasync on a file
250 * @file: file to sync
251 * @dentry: dentry of @file
252 * @datasync: only perform a fdatasync operation
253 *
254 * Write back data and metadata for @file to disk. If @datasync is
255 * set only metadata needed to access modified file data is written.
256 *
257 * In case this function is called from nfsd @file may be %NULL and
258 * only @dentry is set. This can only happen when the filesystem
259 * implements the export_operations API.
260 */
261int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
262{
263    return vfs_fsync_range(file, dentry, 0, LLONG_MAX, datasync);
264}
265EXPORT_SYMBOL(vfs_fsync);
266
267static int do_fsync(unsigned int fd, int datasync)
268{
269    struct file *file;
270    int ret = -EBADF;
271
272    file = fget(fd);
273    if (file) {
274        ret = vfs_fsync(file, file->f_path.dentry, datasync);
275        fput(file);
276    }
277    return ret;
278}
279
280SYSCALL_DEFINE1(fsync, unsigned int, fd)
281{
282    return do_fsync(fd, 0);
283}
284
285SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
286{
287    return do_fsync(fd, 1);
288}
289
290/**
291 * generic_write_sync - perform syncing after a write if file / inode is sync
292 * @file: file to which the write happened
293 * @pos: offset where the write started
294 * @count: length of the write
295 *
296 * This is just a simple wrapper about our general syncing function.
297 */
298int generic_write_sync(struct file *file, loff_t pos, loff_t count)
299{
300    if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
301        return 0;
302    return vfs_fsync_range(file, file->f_path.dentry, pos,
303                   pos + count - 1,
304                   (file->f_flags & __O_SYNC) ? 0 : 1);
305}
306EXPORT_SYMBOL(generic_write_sync);
307
308/*
309 * sys_sync_file_range() permits finely controlled syncing over a segment of
310 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
311 * zero then sys_sync_file_range() will operate from offset out to EOF.
312 *
313 * The flag bits are:
314 *
315 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
316 * before performing the write.
317 *
318 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
319 * range which are not presently under writeback. Note that this may block for
320 * significant periods due to exhaustion of disk request structures.
321 *
322 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
323 * after performing the write.
324 *
325 * Useful combinations of the flag bits are:
326 *
327 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
328 * in the range which were dirty on entry to sys_sync_file_range() are placed
329 * under writeout. This is a start-write-for-data-integrity operation.
330 *
331 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
332 * are not presently under writeout. This is an asynchronous flush-to-disk
333 * operation. Not suitable for data integrity operations.
334 *
335 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
336 * completion of writeout of all pages in the range. This will be used after an
337 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
338 * for that operation to complete and to return the result.
339 *
340 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
341 * a traditional sync() operation. This is a write-for-data-integrity operation
342 * which will ensure that all pages in the range which were dirty on entry to
343 * sys_sync_file_range() are committed to disk.
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 */
355SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
356                unsigned int flags)
357{
358    int ret;
359    struct file *file;
360    struct address_space *mapping;
361    loff_t endbyte; /* inclusive */
362    int fput_needed;
363    umode_t i_mode;
364
365    ret = -EINVAL;
366    if (flags & ~VALID_FLAGS)
367        goto out;
368
369    endbyte = offset + nbytes;
370
371    if ((s64)offset < 0)
372        goto out;
373    if ((s64)endbyte < 0)
374        goto out;
375    if (endbyte < offset)
376        goto out;
377
378    if (sizeof(pgoff_t) == 4) {
379        if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
380            /*
381             * The range starts outside a 32 bit machine's
382             * pagecache addressing capabilities. Let it "succeed"
383             */
384            ret = 0;
385            goto out;
386        }
387        if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
388            /*
389             * Out to EOF
390             */
391            nbytes = 0;
392        }
393    }
394
395    if (nbytes == 0)
396        endbyte = LLONG_MAX;
397    else
398        endbyte--; /* inclusive */
399
400    ret = -EBADF;
401    file = fget_light(fd, &fput_needed);
402    if (!file)
403        goto out;
404
405    i_mode = file->f_path.dentry->d_inode->i_mode;
406    ret = -ESPIPE;
407    if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
408            !S_ISLNK(i_mode))
409        goto out_put;
410
411    mapping = file->f_mapping;
412    if (!mapping) {
413        ret = -EINVAL;
414        goto out_put;
415    }
416
417    ret = 0;
418    if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
419        ret = filemap_fdatawait_range(mapping, offset, endbyte);
420        if (ret < 0)
421            goto out_put;
422    }
423
424    if (flags & SYNC_FILE_RANGE_WRITE) {
425        ret = filemap_fdatawrite_range(mapping, offset, endbyte);
426        if (ret < 0)
427            goto out_put;
428    }
429
430    if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
431        ret = filemap_fdatawait_range(mapping, offset, endbyte);
432
433out_put:
434    fput_light(file, fput_needed);
435out:
436    return ret;
437}
438#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
439asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
440                    long flags)
441{
442    return SYSC_sync_file_range((int) fd, offset, nbytes,
443                    (unsigned int) flags);
444}
445SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
446#endif
447
448/* It would be nice if people remember that not all the world's an i386
449   when they introduce new system calls */
450SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
451                 loff_t offset, loff_t nbytes)
452{
453    return sys_sync_file_range(fd, offset, nbytes, flags);
454}
455#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
456asmlinkage long SyS_sync_file_range2(long fd, long flags,
457                     loff_t offset, loff_t nbytes)
458{
459    return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
460                     offset, nbytes);
461}
462SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
463#endif
464

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