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/module.h>
9#include <linux/sched.h>
10#include <linux/writeback.h>
11#include <linux/syscalls.h>
12#include <linux/linkage.h>
13#include <linux/pagemap.h>
14#include <linux/quotaops.h>
15#include <linux/buffer_head.h>
16#include "internal.h"
17
18#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
19            SYNC_FILE_RANGE_WAIT_AFTER)
20
21/*
22 * Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0)
23 * just dirties buffers with inodes so we have to submit IO for these buffers
24 * via __sync_blockdev(). This also speeds up the wait == 1 case since in that
25 * case write_inode() functions do sync_dirty_buffer() and thus effectively
26 * write one block at a time.
27 */
28static int __sync_filesystem(struct super_block *sb, int wait)
29{
30    /* Avoid doing twice syncing and cache pruning for quota sync */
31    if (!wait)
32        writeout_quota_sb(sb, -1);
33    else
34        sync_quota_sb(sb, -1);
35    sync_inodes_sb(sb, wait);
36    if (sb->s_op->sync_fs)
37        sb->s_op->sync_fs(sb, wait);
38    return __sync_blockdev(sb->s_bdev, wait);
39}
40
41/*
42 * Write out and wait upon all dirty data associated with this
43 * superblock. Filesystem data as well as the underlying block
44 * device. Takes the superblock lock.
45 */
46int sync_filesystem(struct super_block *sb)
47{
48    int ret;
49
50    /*
51     * We need to be protected against the filesystem going from
52     * r/o to r/w or vice versa.
53     */
54    WARN_ON(!rwsem_is_locked(&sb->s_umount));
55
56    /*
57     * No point in syncing out anything if the filesystem is read-only.
58     */
59    if (sb->s_flags & MS_RDONLY)
60        return 0;
61
62    ret = __sync_filesystem(sb, 0);
63    if (ret < 0)
64        return ret;
65    return __sync_filesystem(sb, 1);
66}
67EXPORT_SYMBOL_GPL(sync_filesystem);
68
69/*
70 * Sync all the data for all the filesystems (called by sys_sync() and
71 * emergency sync)
72 *
73 * This operation is careful to avoid the livelock which could easily happen
74 * if two or more filesystems are being continuously dirtied. s_need_sync
75 * is used only here. We set it against all filesystems and then clear it as
76 * we sync them. So redirtied filesystems are skipped.
77 *
78 * But if process A is currently running sync_filesystems and then process B
79 * calls sync_filesystems as well, process B will set all the s_need_sync
80 * flags again, which will cause process A to resync everything. Fix that with
81 * a local mutex.
82 */
83static void sync_filesystems(int wait)
84{
85    struct super_block *sb;
86    static DEFINE_MUTEX(mutex);
87
88    mutex_lock(&mutex); /* Could be down_interruptible */
89    spin_lock(&sb_lock);
90    list_for_each_entry(sb, &super_blocks, s_list)
91        sb->s_need_sync = 1;
92
93restart:
94    list_for_each_entry(sb, &super_blocks, s_list) {
95        if (!sb->s_need_sync)
96            continue;
97        sb->s_need_sync = 0;
98        sb->s_count++;
99        spin_unlock(&sb_lock);
100
101        down_read(&sb->s_umount);
102        if (!(sb->s_flags & MS_RDONLY) && sb->s_root)
103            __sync_filesystem(sb, wait);
104        up_read(&sb->s_umount);
105
106        /* restart only when sb is no longer on the list */
107        spin_lock(&sb_lock);
108        if (__put_super_and_need_restart(sb))
109            goto restart;
110    }
111    spin_unlock(&sb_lock);
112    mutex_unlock(&mutex);
113}
114
115/*
116 * sync everything. Start out by waking pdflush, because that writes back
117 * all queues in parallel.
118 */
119SYSCALL_DEFINE0(sync)
120{
121    wakeup_pdflush(0);
122    sync_filesystems(0);
123    sync_filesystems(1);
124    if (unlikely(laptop_mode))
125        laptop_sync_completion();
126    return 0;
127}
128
129static void do_sync_work(struct work_struct *work)
130{
131    /*
132     * Sync twice to reduce the possibility we skipped some inodes / pages
133     * because they were temporarily locked
134     */
135    sync_filesystems(0);
136    sync_filesystems(0);
137    printk("Emergency Sync complete\n");
138    kfree(work);
139}
140
141void emergency_sync(void)
142{
143    struct work_struct *work;
144
145    work = kmalloc(sizeof(*work), GFP_ATOMIC);
146    if (work) {
147        INIT_WORK(work, do_sync_work);
148        schedule_work(work);
149    }
150}
151
152/*
153 * Generic function to fsync a file.
154 *
155 * filp may be NULL if called via the msync of a vma.
156 */
157int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
158{
159    struct inode * inode = dentry->d_inode;
160    struct super_block * sb;
161    int ret, err;
162
163    /* sync the inode to buffers */
164    ret = write_inode_now(inode, 0);
165
166    /* sync the superblock to buffers */
167    sb = inode->i_sb;
168    if (sb->s_dirt && sb->s_op->write_super)
169        sb->s_op->write_super(sb);
170
171    /* .. finally sync the buffers to disk */
172    err = sync_blockdev(sb->s_bdev);
173    if (!ret)
174        ret = err;
175    return ret;
176}
177
178/**
179 * vfs_fsync - perform a fsync or fdatasync on a file
180 * @file: file to sync
181 * @dentry: dentry of @file
182 * @data: only perform a fdatasync operation
183 *
184 * Write back data and metadata for @file to disk. If @datasync is
185 * set only metadata needed to access modified file data is written.
186 *
187 * In case this function is called from nfsd @file may be %NULL and
188 * only @dentry is set. This can only happen when the filesystem
189 * implements the export_operations API.
190 */
191int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
192{
193    const struct file_operations *fop;
194    struct address_space *mapping;
195    int err, ret;
196
197    /*
198     * Get mapping and operations from the file in case we have
199     * as file, or get the default values for them in case we
200     * don't have a struct file available. Damn nfsd..
201     */
202    if (file) {
203        mapping = file->f_mapping;
204        fop = file->f_op;
205    } else {
206        mapping = dentry->d_inode->i_mapping;
207        fop = dentry->d_inode->i_fop;
208    }
209
210    if (!fop || !fop->fsync) {
211        ret = -EINVAL;
212        goto out;
213    }
214
215    ret = filemap_fdatawrite(mapping);
216
217    /*
218     * We need to protect against concurrent writers, which could cause
219     * livelocks in fsync_buffers_list().
220     */
221    mutex_lock(&mapping->host->i_mutex);
222    err = fop->fsync(file, dentry, datasync);
223    if (!ret)
224        ret = err;
225    mutex_unlock(&mapping->host->i_mutex);
226    err = filemap_fdatawait(mapping);
227    if (!ret)
228        ret = err;
229out:
230    return ret;
231}
232EXPORT_SYMBOL(vfs_fsync);
233
234static int do_fsync(unsigned int fd, int datasync)
235{
236    struct file *file;
237    int ret = -EBADF;
238
239    file = fget(fd);
240    if (file) {
241        ret = vfs_fsync(file, file->f_path.dentry, datasync);
242        fput(file);
243    }
244    return ret;
245}
246
247SYSCALL_DEFINE1(fsync, unsigned int, fd)
248{
249    return do_fsync(fd, 0);
250}
251
252SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
253{
254    return do_fsync(fd, 1);
255}
256
257/*
258 * sys_sync_file_range() permits finely controlled syncing over a segment of
259 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
260 * zero then sys_sync_file_range() will operate from offset out to EOF.
261 *
262 * The flag bits are:
263 *
264 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
265 * before performing the write.
266 *
267 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
268 * range which are not presently under writeback. Note that this may block for
269 * significant periods due to exhaustion of disk request structures.
270 *
271 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
272 * after performing the write.
273 *
274 * Useful combinations of the flag bits are:
275 *
276 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
277 * in the range which were dirty on entry to sys_sync_file_range() are placed
278 * under writeout. This is a start-write-for-data-integrity operation.
279 *
280 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
281 * are not presently under writeout. This is an asynchronous flush-to-disk
282 * operation. Not suitable for data integrity operations.
283 *
284 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
285 * completion of writeout of all pages in the range. This will be used after an
286 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
287 * for that operation to complete and to return the result.
288 *
289 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
290 * a traditional sync() operation. This is a write-for-data-integrity operation
291 * which will ensure that all pages in the range which were dirty on entry to
292 * sys_sync_file_range() are committed to disk.
293 *
294 *
295 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
296 * I/O errors or ENOSPC conditions and will return those to the caller, after
297 * clearing the EIO and ENOSPC flags in the address_space.
298 *
299 * It should be noted that none of these operations write out the file's
300 * metadata. So unless the application is strictly performing overwrites of
301 * already-instantiated disk blocks, there are no guarantees here that the data
302 * will be available after a crash.
303 */
304SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
305                unsigned int flags)
306{
307    int ret;
308    struct file *file;
309    loff_t endbyte; /* inclusive */
310    int fput_needed;
311    umode_t i_mode;
312
313    ret = -EINVAL;
314    if (flags & ~VALID_FLAGS)
315        goto out;
316
317    endbyte = offset + nbytes;
318
319    if ((s64)offset < 0)
320        goto out;
321    if ((s64)endbyte < 0)
322        goto out;
323    if (endbyte < offset)
324        goto out;
325
326    if (sizeof(pgoff_t) == 4) {
327        if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
328            /*
329             * The range starts outside a 32 bit machine's
330             * pagecache addressing capabilities. Let it "succeed"
331             */
332            ret = 0;
333            goto out;
334        }
335        if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
336            /*
337             * Out to EOF
338             */
339            nbytes = 0;
340        }
341    }
342
343    if (nbytes == 0)
344        endbyte = LLONG_MAX;
345    else
346        endbyte--; /* inclusive */
347
348    ret = -EBADF;
349    file = fget_light(fd, &fput_needed);
350    if (!file)
351        goto out;
352
353    i_mode = file->f_path.dentry->d_inode->i_mode;
354    ret = -ESPIPE;
355    if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
356            !S_ISLNK(i_mode))
357        goto out_put;
358
359    ret = do_sync_mapping_range(file->f_mapping, offset, endbyte, flags);
360out_put:
361    fput_light(file, fput_needed);
362out:
363    return ret;
364}
365#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
366asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
367                    long flags)
368{
369    return SYSC_sync_file_range((int) fd, offset, nbytes,
370                    (unsigned int) flags);
371}
372SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
373#endif
374
375/* It would be nice if people remember that not all the world's an i386
376   when they introduce new system calls */
377SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
378                 loff_t offset, loff_t nbytes)
379{
380    return sys_sync_file_range(fd, offset, nbytes, flags);
381}
382#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
383asmlinkage long SyS_sync_file_range2(long fd, long flags,
384                     loff_t offset, loff_t nbytes)
385{
386    return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
387                     offset, nbytes);
388}
389SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
390#endif
391
392/*
393 * `endbyte' is inclusive
394 */
395int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
396              loff_t endbyte, unsigned int flags)
397{
398    int ret;
399
400    if (!mapping) {
401        ret = -EINVAL;
402        goto out;
403    }
404
405    ret = 0;
406    if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
407        ret = wait_on_page_writeback_range(mapping,
408                    offset >> PAGE_CACHE_SHIFT,
409                    endbyte >> PAGE_CACHE_SHIFT);
410        if (ret < 0)
411            goto out;
412    }
413
414    if (flags & SYNC_FILE_RANGE_WRITE) {
415        ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
416                        WB_SYNC_ALL);
417        if (ret < 0)
418            goto out;
419    }
420
421    if (flags & SYNC_FILE_RANGE_WAIT_AFTER) {
422        ret = wait_on_page_writeback_range(mapping,
423                    offset >> PAGE_CACHE_SHIFT,
424                    endbyte >> PAGE_CACHE_SHIFT);
425    }
426out:
427    return ret;
428}
429EXPORT_SYMBOL_GPL(do_sync_mapping_range);
430

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