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/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);
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);
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    struct address_space *mapping = file->f_mapping;
169    int err, ret;
170
171    if (!file->f_op || !file->f_op->fsync) {
172        ret = -EINVAL;
173        goto out;
174    }
175
176    ret = filemap_write_and_wait_range(mapping, start, end);
177
178    /*
179     * We need to protect against concurrent writers, which could cause
180     * livelocks in fsync_buffers_list().
181     */
182    mutex_lock(&mapping->host->i_mutex);
183    err = file->f_op->fsync(file, datasync);
184    if (!ret)
185        ret = err;
186    mutex_unlock(&mapping->host->i_mutex);
187
188out:
189    return ret;
190}
191EXPORT_SYMBOL(vfs_fsync_range);
192
193/**
194 * vfs_fsync - perform a fsync or fdatasync on a file
195 * @file: file to sync
196 * @datasync: only perform a fdatasync operation
197 *
198 * Write back data and metadata for @file to disk. If @datasync is
199 * set only metadata needed to access modified file data is written.
200 */
201int vfs_fsync(struct file *file, int datasync)
202{
203    return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
204}
205EXPORT_SYMBOL(vfs_fsync);
206
207static int do_fsync(unsigned int fd, int datasync)
208{
209    struct file *file;
210    int ret = -EBADF;
211
212    file = fget(fd);
213    if (file) {
214        ret = vfs_fsync(file, datasync);
215        fput(file);
216    }
217    return ret;
218}
219
220SYSCALL_DEFINE1(fsync, unsigned int, fd)
221{
222    return do_fsync(fd, 0);
223}
224
225SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
226{
227    return do_fsync(fd, 1);
228}
229
230/**
231 * generic_write_sync - perform syncing after a write if file / inode is sync
232 * @file: file to which the write happened
233 * @pos: offset where the write started
234 * @count: length of the write
235 *
236 * This is just a simple wrapper about our general syncing function.
237 */
238int generic_write_sync(struct file *file, loff_t pos, loff_t count)
239{
240    if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
241        return 0;
242    return vfs_fsync_range(file, pos, pos + count - 1,
243                   (file->f_flags & __O_SYNC) ? 0 : 1);
244}
245EXPORT_SYMBOL(generic_write_sync);
246
247/*
248 * sys_sync_file_range() permits finely controlled syncing over a segment of
249 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
250 * zero then sys_sync_file_range() will operate from offset out to EOF.
251 *
252 * The flag bits are:
253 *
254 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
255 * before performing the write.
256 *
257 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
258 * range which are not presently under writeback. Note that this may block for
259 * significant periods due to exhaustion of disk request structures.
260 *
261 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
262 * after performing the write.
263 *
264 * Useful combinations of the flag bits are:
265 *
266 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
267 * in the range which were dirty on entry to sys_sync_file_range() are placed
268 * under writeout. This is a start-write-for-data-integrity operation.
269 *
270 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
271 * are not presently under writeout. This is an asynchronous flush-to-disk
272 * operation. Not suitable for data integrity operations.
273 *
274 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
275 * completion of writeout of all pages in the range. This will be used after an
276 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
277 * for that operation to complete and to return the result.
278 *
279 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
280 * a traditional sync() operation. This is a write-for-data-integrity operation
281 * which will ensure that all pages in the range which were dirty on entry to
282 * sys_sync_file_range() are committed to disk.
283 *
284 *
285 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
286 * I/O errors or ENOSPC conditions and will return those to the caller, after
287 * clearing the EIO and ENOSPC flags in the address_space.
288 *
289 * It should be noted that none of these operations write out the file's
290 * metadata. So unless the application is strictly performing overwrites of
291 * already-instantiated disk blocks, there are no guarantees here that the data
292 * will be available after a crash.
293 */
294SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
295                unsigned int flags)
296{
297    int ret;
298    struct file *file;
299    struct address_space *mapping;
300    loff_t endbyte; /* inclusive */
301    int fput_needed;
302    umode_t i_mode;
303
304    ret = -EINVAL;
305    if (flags & ~VALID_FLAGS)
306        goto out;
307
308    endbyte = offset + nbytes;
309
310    if ((s64)offset < 0)
311        goto out;
312    if ((s64)endbyte < 0)
313        goto out;
314    if (endbyte < offset)
315        goto out;
316
317    if (sizeof(pgoff_t) == 4) {
318        if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
319            /*
320             * The range starts outside a 32 bit machine's
321             * pagecache addressing capabilities. Let it "succeed"
322             */
323            ret = 0;
324            goto out;
325        }
326        if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
327            /*
328             * Out to EOF
329             */
330            nbytes = 0;
331        }
332    }
333
334    if (nbytes == 0)
335        endbyte = LLONG_MAX;
336    else
337        endbyte--; /* inclusive */
338
339    ret = -EBADF;
340    file = fget_light(fd, &fput_needed);
341    if (!file)
342        goto out;
343
344    i_mode = file->f_path.dentry->d_inode->i_mode;
345    ret = -ESPIPE;
346    if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
347            !S_ISLNK(i_mode))
348        goto out_put;
349
350    mapping = file->f_mapping;
351    if (!mapping) {
352        ret = -EINVAL;
353        goto out_put;
354    }
355
356    ret = 0;
357    if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
358        ret = filemap_fdatawait_range(mapping, offset, endbyte);
359        if (ret < 0)
360            goto out_put;
361    }
362
363    if (flags & SYNC_FILE_RANGE_WRITE) {
364        ret = filemap_fdatawrite_range(mapping, offset, endbyte);
365        if (ret < 0)
366            goto out_put;
367    }
368
369    if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
370        ret = filemap_fdatawait_range(mapping, offset, endbyte);
371
372out_put:
373    fput_light(file, fput_needed);
374out:
375    return ret;
376}
377#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
378asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
379                    long flags)
380{
381    return SYSC_sync_file_range((int) fd, offset, nbytes,
382                    (unsigned int) flags);
383}
384SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
385#endif
386
387/* It would be nice if people remember that not all the world's an i386
388   when they introduce new system calls */
389SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
390                 loff_t offset, loff_t nbytes)
391{
392    return sys_sync_file_range(fd, offset, nbytes, flags);
393}
394#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
395asmlinkage long SyS_sync_file_range2(long fd, long flags,
396                     loff_t offset, loff_t nbytes)
397{
398    return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
399                     offset, nbytes);
400}
401SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
402#endif
403

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