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 "internal.h"
18
19#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
20            SYNC_FILE_RANGE_WAIT_AFTER)
21
22/*
23 * Do the filesystem syncing work. For simple filesystems
24 * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
25 * submit IO for these buffers via __sync_blockdev(). This also speeds up the
26 * wait == 1 case since in that case write_inode() functions do
27 * sync_dirty_buffer() and thus effectively write one block at a time.
28 */
29static int __sync_filesystem(struct super_block *sb, int wait)
30{
31    /*
32     * This should be safe, as we require bdi backing to actually
33     * write out data in the first place
34     */
35    if (!sb->s_bdi)
36        return 0;
37
38    if (sb->s_qcop && sb->s_qcop->quota_sync)
39        sb->s_qcop->quota_sync(sb, -1, wait);
40
41    if (wait)
42        sync_inodes_sb(sb);
43    else
44        writeback_inodes_sb(sb);
45
46    if (sb->s_op->sync_fs)
47        sb->s_op->sync_fs(sb, wait);
48    return __sync_blockdev(sb->s_bdev, wait);
49}
50
51/*
52 * Write out and wait upon all dirty data associated with this
53 * superblock. Filesystem data as well as the underlying block
54 * device. Takes the superblock lock.
55 */
56int sync_filesystem(struct super_block *sb)
57{
58    int ret;
59
60    /*
61     * We need to be protected against the filesystem going from
62     * r/o to r/w or vice versa.
63     */
64    WARN_ON(!rwsem_is_locked(&sb->s_umount));
65
66    /*
67     * No point in syncing out anything if the filesystem is read-only.
68     */
69    if (sb->s_flags & MS_RDONLY)
70        return 0;
71
72    ret = __sync_filesystem(sb, 0);
73    if (ret < 0)
74        return ret;
75    return __sync_filesystem(sb, 1);
76}
77EXPORT_SYMBOL_GPL(sync_filesystem);
78
79/*
80 * Sync all the data for all the filesystems (called by sys_sync() and
81 * emergency sync)
82 *
83 * This operation is careful to avoid the livelock which could easily happen
84 * if two or more filesystems are being continuously dirtied. s_need_sync
85 * is used only here. We set it against all filesystems and then clear it as
86 * we sync them. So redirtied filesystems are skipped.
87 *
88 * But if process A is currently running sync_filesystems and then process B
89 * calls sync_filesystems as well, process B will set all the s_need_sync
90 * flags again, which will cause process A to resync everything. Fix that with
91 * a local mutex.
92 */
93static void sync_filesystems(int wait)
94{
95    struct super_block *sb;
96    static DEFINE_MUTEX(mutex);
97
98    mutex_lock(&mutex); /* Could be down_interruptible */
99    spin_lock(&sb_lock);
100    list_for_each_entry(sb, &super_blocks, s_list)
101        sb->s_need_sync = 1;
102
103restart:
104    list_for_each_entry(sb, &super_blocks, s_list) {
105        if (!sb->s_need_sync)
106            continue;
107        sb->s_need_sync = 0;
108        sb->s_count++;
109        spin_unlock(&sb_lock);
110
111        down_read(&sb->s_umount);
112        if (!(sb->s_flags & MS_RDONLY) && sb->s_root && sb->s_bdi)
113            __sync_filesystem(sb, wait);
114        up_read(&sb->s_umount);
115
116        /* restart only when sb is no longer on the list */
117        spin_lock(&sb_lock);
118        if (__put_super_and_need_restart(sb))
119            goto restart;
120    }
121    spin_unlock(&sb_lock);
122    mutex_unlock(&mutex);
123}
124
125/*
126 * sync everything. Start out by waking pdflush, because that writes back
127 * all queues in parallel.
128 */
129SYSCALL_DEFINE0(sync)
130{
131    wakeup_flusher_threads(0);
132    sync_filesystems(0);
133    sync_filesystems(1);
134    if (unlikely(laptop_mode))
135        laptop_sync_completion();
136    return 0;
137}
138
139static void do_sync_work(struct work_struct *work)
140{
141    /*
142     * Sync twice to reduce the possibility we skipped some inodes / pages
143     * because they were temporarily locked
144     */
145    sync_filesystems(0);
146    sync_filesystems(0);
147    printk("Emergency Sync complete\n");
148    kfree(work);
149}
150
151void emergency_sync(void)
152{
153    struct work_struct *work;
154
155    work = kmalloc(sizeof(*work), GFP_ATOMIC);
156    if (work) {
157        INIT_WORK(work, do_sync_work);
158        schedule_work(work);
159    }
160}
161
162/*
163 * Generic function to fsync a file.
164 *
165 * filp may be NULL if called via the msync of a vma.
166 */
167int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
168{
169    struct inode * inode = dentry->d_inode;
170    struct super_block * sb;
171    int ret, err;
172
173    /* sync the inode to buffers */
174    ret = write_inode_now(inode, 0);
175
176    /* sync the superblock to buffers */
177    sb = inode->i_sb;
178    if (sb->s_dirt && sb->s_op->write_super)
179        sb->s_op->write_super(sb);
180
181    /* .. finally sync the buffers to disk */
182    err = sync_blockdev(sb->s_bdev);
183    if (!ret)
184        ret = err;
185    return ret;
186}
187EXPORT_SYMBOL(file_fsync);
188
189/**
190 * vfs_fsync_range - helper to sync a range of data & metadata to disk
191 * @file: file to sync
192 * @dentry: dentry of @file
193 * @start: offset in bytes of the beginning of data range to sync
194 * @end: offset in bytes of the end of data range (inclusive)
195 * @datasync: perform only datasync
196 *
197 * Write back data in range @start..@end and metadata for @file to disk. If
198 * @datasync is set only metadata needed to access modified file data is
199 * written.
200 *
201 * In case this function is called from nfsd @file may be %NULL and
202 * only @dentry is set. This can only happen when the filesystem
203 * implements the export_operations API.
204 */
205int vfs_fsync_range(struct file *file, struct dentry *dentry, loff_t start,
206            loff_t end, int datasync)
207{
208    const struct file_operations *fop;
209    struct address_space *mapping;
210    int err, ret;
211
212    /*
213     * Get mapping and operations from the file in case we have
214     * as file, or get the default values for them in case we
215     * don't have a struct file available. Damn nfsd..
216     */
217    if (file) {
218        mapping = file->f_mapping;
219        fop = file->f_op;
220    } else {
221        mapping = dentry->d_inode->i_mapping;
222        fop = dentry->d_inode->i_fop;
223    }
224
225    if (!fop || !fop->fsync) {
226        ret = -EINVAL;
227        goto out;
228    }
229
230    ret = filemap_write_and_wait_range(mapping, start, end);
231
232    /*
233     * We need to protect against concurrent writers, which could cause
234     * livelocks in fsync_buffers_list().
235     */
236    mutex_lock(&mapping->host->i_mutex);
237    err = fop->fsync(file, dentry, datasync);
238    if (!ret)
239        ret = err;
240    mutex_unlock(&mapping->host->i_mutex);
241
242out:
243    return ret;
244}
245EXPORT_SYMBOL(vfs_fsync_range);
246
247/**
248 * vfs_fsync - perform a fsync or fdatasync on a file
249 * @file: file to sync
250 * @dentry: dentry of @file
251 * @datasync: only perform a fdatasync operation
252 *
253 * Write back data and metadata for @file to disk. If @datasync is
254 * set only metadata needed to access modified file data is written.
255 *
256 * In case this function is called from nfsd @file may be %NULL and
257 * only @dentry is set. This can only happen when the filesystem
258 * implements the export_operations API.
259 */
260int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
261{
262    return vfs_fsync_range(file, dentry, 0, LLONG_MAX, datasync);
263}
264EXPORT_SYMBOL(vfs_fsync);
265
266static int do_fsync(unsigned int fd, int datasync)
267{
268    struct file *file;
269    int ret = -EBADF;
270
271    file = fget(fd);
272    if (file) {
273        ret = vfs_fsync(file, file->f_path.dentry, datasync);
274        fput(file);
275    }
276    return ret;
277}
278
279SYSCALL_DEFINE1(fsync, unsigned int, fd)
280{
281    return do_fsync(fd, 0);
282}
283
284SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
285{
286    return do_fsync(fd, 1);
287}
288
289/**
290 * generic_write_sync - perform syncing after a write if file / inode is sync
291 * @file: file to which the write happened
292 * @pos: offset where the write started
293 * @count: length of the write
294 *
295 * This is just a simple wrapper about our general syncing function.
296 */
297int generic_write_sync(struct file *file, loff_t pos, loff_t count)
298{
299    if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
300        return 0;
301    return vfs_fsync_range(file, file->f_path.dentry, pos,
302                   pos + count - 1,
303                   (file->f_flags & __O_SYNC) ? 0 : 1);
304}
305EXPORT_SYMBOL(generic_write_sync);
306
307/*
308 * sys_sync_file_range() permits finely controlled syncing over a segment of
309 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
310 * zero then sys_sync_file_range() will operate from offset out to EOF.
311 *
312 * The flag bits are:
313 *
314 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
315 * before performing the write.
316 *
317 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
318 * range which are not presently under writeback. Note that this may block for
319 * significant periods due to exhaustion of disk request structures.
320 *
321 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
322 * after performing the write.
323 *
324 * Useful combinations of the flag bits are:
325 *
326 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
327 * in the range which were dirty on entry to sys_sync_file_range() are placed
328 * under writeout. This is a start-write-for-data-integrity operation.
329 *
330 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
331 * are not presently under writeout. This is an asynchronous flush-to-disk
332 * operation. Not suitable for data integrity operations.
333 *
334 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
335 * completion of writeout of all pages in the range. This will be used after an
336 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
337 * for that operation to complete and to return the result.
338 *
339 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
340 * a traditional sync() operation. This is a write-for-data-integrity operation
341 * which will ensure that all pages in the range which were dirty on entry to
342 * sys_sync_file_range() are committed to disk.
343 *
344 *
345 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
346 * I/O errors or ENOSPC conditions and will return those to the caller, after
347 * clearing the EIO and ENOSPC flags in the address_space.
348 *
349 * It should be noted that none of these operations write out the file's
350 * metadata. So unless the application is strictly performing overwrites of
351 * already-instantiated disk blocks, there are no guarantees here that the data
352 * will be available after a crash.
353 */
354SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
355                unsigned int flags)
356{
357    int ret;
358    struct file *file;
359    struct address_space *mapping;
360    loff_t endbyte; /* inclusive */
361    int fput_needed;
362    umode_t i_mode;
363
364    ret = -EINVAL;
365    if (flags & ~VALID_FLAGS)
366        goto out;
367
368    endbyte = offset + nbytes;
369
370    if ((s64)offset < 0)
371        goto out;
372    if ((s64)endbyte < 0)
373        goto out;
374    if (endbyte < offset)
375        goto out;
376
377    if (sizeof(pgoff_t) == 4) {
378        if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
379            /*
380             * The range starts outside a 32 bit machine's
381             * pagecache addressing capabilities. Let it "succeed"
382             */
383            ret = 0;
384            goto out;
385        }
386        if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
387            /*
388             * Out to EOF
389             */
390            nbytes = 0;
391        }
392    }
393
394    if (nbytes == 0)
395        endbyte = LLONG_MAX;
396    else
397        endbyte--; /* inclusive */
398
399    ret = -EBADF;
400    file = fget_light(fd, &fput_needed);
401    if (!file)
402        goto out;
403
404    i_mode = file->f_path.dentry->d_inode->i_mode;
405    ret = -ESPIPE;
406    if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
407            !S_ISLNK(i_mode))
408        goto out_put;
409
410    mapping = file->f_mapping;
411    if (!mapping) {
412        ret = -EINVAL;
413        goto out_put;
414    }
415
416    ret = 0;
417    if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
418        ret = filemap_fdatawait_range(mapping, offset, endbyte);
419        if (ret < 0)
420            goto out_put;
421    }
422
423    if (flags & SYNC_FILE_RANGE_WRITE) {
424        ret = filemap_fdatawrite_range(mapping, offset, endbyte);
425        if (ret < 0)
426            goto out_put;
427    }
428
429    if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
430        ret = filemap_fdatawait_range(mapping, offset, endbyte);
431
432out_put:
433    fput_light(file, fput_needed);
434out:
435    return ret;
436}
437#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
438asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
439                    long flags)
440{
441    return SYSC_sync_file_range((int) fd, offset, nbytes,
442                    (unsigned int) flags);
443}
444SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
445#endif
446
447/* It would be nice if people remember that not all the world's an i386
448   when they introduce new system calls */
449SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
450                 loff_t offset, loff_t nbytes)
451{
452    return sys_sync_file_range(fd, offset, nbytes, flags);
453}
454#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
455asmlinkage long SyS_sync_file_range2(long fd, long flags,
456                     loff_t offset, loff_t nbytes)
457{
458    return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
459                     offset, nbytes);
460}
461SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
462#endif
463

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