The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/fs/sync.c

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    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/export.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/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  */
   30 static int __sync_filesystem(struct super_block *sb, int wait)
   31 {
   32         if (wait)
   33                 sync_inodes_sb(sb);
   34         else
   35                 writeback_inodes_sb(sb, WB_REASON_SYNC);
   36 
   37         if (sb->s_op->sync_fs)
   38                 sb->s_op->sync_fs(sb, wait);
   39         return __sync_blockdev(sb->s_bdev, wait);
   40 }
   41 
   42 /*
   43  * Write out and wait upon all dirty data associated with this
   44  * superblock.  Filesystem data as well as the underlying block
   45  * device.  Takes the superblock lock.
   46  */
   47 int sync_filesystem(struct super_block *sb)
   48 {
   49         int ret;
   50 
   51         /*
   52          * We need to be protected against the filesystem going from
   53          * r/o to r/w or vice versa.
   54          */
   55         WARN_ON(!rwsem_is_locked(&sb->s_umount));
   56 
   57         /*
   58          * No point in syncing out anything if the filesystem is read-only.
   59          */
   60         if (sb->s_flags & MS_RDONLY)
   61                 return 0;
   62 
   63         ret = __sync_filesystem(sb, 0);
   64         if (ret < 0)
   65                 return ret;
   66         return __sync_filesystem(sb, 1);
   67 }
   68 EXPORT_SYMBOL_GPL(sync_filesystem);
   69 
   70 static void sync_inodes_one_sb(struct super_block *sb, void *arg)
   71 {
   72         if (!(sb->s_flags & MS_RDONLY))
   73                 sync_inodes_sb(sb);
   74 }
   75 
   76 static void sync_fs_one_sb(struct super_block *sb, void *arg)
   77 {
   78         if (!(sb->s_flags & MS_RDONLY) && sb->s_op->sync_fs)
   79                 sb->s_op->sync_fs(sb, *(int *)arg);
   80 }
   81 
   82 static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
   83 {
   84         filemap_fdatawrite(bdev->bd_inode->i_mapping);
   85 }
   86 
   87 static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
   88 {
   89         filemap_fdatawait(bdev->bd_inode->i_mapping);
   90 }
   91 
   92 /*
   93  * Sync everything. We start by waking flusher threads so that most of
   94  * writeback runs on all devices in parallel. Then we sync all inodes reliably
   95  * which effectively also waits for all flusher threads to finish doing
   96  * writeback. At this point all data is on disk so metadata should be stable
   97  * and we tell filesystems to sync their metadata via ->sync_fs() calls.
   98  * Finally, we writeout all block devices because some filesystems (e.g. ext2)
   99  * just write metadata (such as inodes or bitmaps) to block device page cache
  100  * and do not sync it on their own in ->sync_fs().
  101  */
  102 SYSCALL_DEFINE0(sync)
  103 {
  104         int nowait = 0, wait = 1;
  105 
  106         wakeup_flusher_threads(0, WB_REASON_SYNC);
  107         iterate_supers(sync_inodes_one_sb, NULL);
  108         iterate_supers(sync_fs_one_sb, &nowait);
  109         iterate_supers(sync_fs_one_sb, &wait);
  110         iterate_bdevs(fdatawrite_one_bdev, NULL);
  111         iterate_bdevs(fdatawait_one_bdev, NULL);
  112         if (unlikely(laptop_mode))
  113                 laptop_sync_completion();
  114         return 0;
  115 }
  116 
  117 static void do_sync_work(struct work_struct *work)
  118 {
  119         int nowait = 0;
  120 
  121         /*
  122          * Sync twice to reduce the possibility we skipped some inodes / pages
  123          * because they were temporarily locked
  124          */
  125         iterate_supers(sync_inodes_one_sb, &nowait);
  126         iterate_supers(sync_fs_one_sb, &nowait);
  127         iterate_bdevs(fdatawrite_one_bdev, NULL);
  128         iterate_supers(sync_inodes_one_sb, &nowait);
  129         iterate_supers(sync_fs_one_sb, &nowait);
  130         iterate_bdevs(fdatawrite_one_bdev, NULL);
  131         printk("Emergency Sync complete\n");
  132         kfree(work);
  133 }
  134 
  135 void emergency_sync(void)
  136 {
  137         struct work_struct *work;
  138 
  139         work = kmalloc(sizeof(*work), GFP_ATOMIC);
  140         if (work) {
  141                 INIT_WORK(work, do_sync_work);
  142                 schedule_work(work);
  143         }
  144 }
  145 
  146 /*
  147  * sync a single super
  148  */
  149 SYSCALL_DEFINE1(syncfs, int, fd)
  150 {
  151         struct fd f = fdget(fd);
  152         struct super_block *sb;
  153         int ret;
  154 
  155         if (!f.file)
  156                 return -EBADF;
  157         sb = f.file->f_dentry->d_sb;
  158 
  159         down_read(&sb->s_umount);
  160         ret = sync_filesystem(sb);
  161         up_read(&sb->s_umount);
  162 
  163         fdput(f);
  164         return ret;
  165 }
  166 
  167 /**
  168  * vfs_fsync_range - helper to sync a range of data & metadata to disk
  169  * @file:               file to sync
  170  * @start:              offset in bytes of the beginning of data range to sync
  171  * @end:                offset in bytes of the end of data range (inclusive)
  172  * @datasync:           perform only datasync
  173  *
  174  * Write back data in range @start..@end and metadata for @file to disk.  If
  175  * @datasync is set only metadata needed to access modified file data is
  176  * written.
  177  */
  178 int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
  179 {
  180         if (!file->f_op || !file->f_op->fsync)
  181                 return -EINVAL;
  182         return file->f_op->fsync(file, start, end, datasync);
  183 }
  184 EXPORT_SYMBOL(vfs_fsync_range);
  185 
  186 /**
  187  * vfs_fsync - perform a fsync or fdatasync on a file
  188  * @file:               file to sync
  189  * @datasync:           only perform a fdatasync operation
  190  *
  191  * Write back data and metadata for @file to disk.  If @datasync is
  192  * set only metadata needed to access modified file data is written.
  193  */
  194 int vfs_fsync(struct file *file, int datasync)
  195 {
  196         return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
  197 }
  198 EXPORT_SYMBOL(vfs_fsync);
  199 
  200 static int do_fsync(unsigned int fd, int datasync)
  201 {
  202         struct fd f = fdget(fd);
  203         int ret = -EBADF;
  204 
  205         if (f.file) {
  206                 ret = vfs_fsync(f.file, datasync);
  207                 fdput(f);
  208         }
  209         return ret;
  210 }
  211 
  212 SYSCALL_DEFINE1(fsync, unsigned int, fd)
  213 {
  214         return do_fsync(fd, 0);
  215 }
  216 
  217 SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
  218 {
  219         return do_fsync(fd, 1);
  220 }
  221 
  222 /**
  223  * generic_write_sync - perform syncing after a write if file / inode is sync
  224  * @file:       file to which the write happened
  225  * @pos:        offset where the write started
  226  * @count:      length of the write
  227  *
  228  * This is just a simple wrapper about our general syncing function.
  229  */
  230 int generic_write_sync(struct file *file, loff_t pos, loff_t count)
  231 {
  232         if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
  233                 return 0;
  234         return vfs_fsync_range(file, pos, pos + count - 1,
  235                                (file->f_flags & __O_SYNC) ? 0 : 1);
  236 }
  237 EXPORT_SYMBOL(generic_write_sync);
  238 
  239 /*
  240  * sys_sync_file_range() permits finely controlled syncing over a segment of
  241  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
  242  * zero then sys_sync_file_range() will operate from offset out to EOF.
  243  *
  244  * The flag bits are:
  245  *
  246  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
  247  * before performing the write.
  248  *
  249  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
  250  * range which are not presently under writeback. Note that this may block for
  251  * significant periods due to exhaustion of disk request structures.
  252  *
  253  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
  254  * after performing the write.
  255  *
  256  * Useful combinations of the flag bits are:
  257  *
  258  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
  259  * in the range which were dirty on entry to sys_sync_file_range() are placed
  260  * under writeout.  This is a start-write-for-data-integrity operation.
  261  *
  262  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
  263  * are not presently under writeout.  This is an asynchronous flush-to-disk
  264  * operation.  Not suitable for data integrity operations.
  265  *
  266  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
  267  * completion of writeout of all pages in the range.  This will be used after an
  268  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
  269  * for that operation to complete and to return the result.
  270  *
  271  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
  272  * a traditional sync() operation.  This is a write-for-data-integrity operation
  273  * which will ensure that all pages in the range which were dirty on entry to
  274  * sys_sync_file_range() are committed to disk.
  275  *
  276  *
  277  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
  278  * I/O errors or ENOSPC conditions and will return those to the caller, after
  279  * clearing the EIO and ENOSPC flags in the address_space.
  280  *
  281  * It should be noted that none of these operations write out the file's
  282  * metadata.  So unless the application is strictly performing overwrites of
  283  * already-instantiated disk blocks, there are no guarantees here that the data
  284  * will be available after a crash.
  285  */
  286 SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
  287                                 unsigned int flags)
  288 {
  289         int ret;
  290         struct fd f;
  291         struct address_space *mapping;
  292         loff_t endbyte;                 /* inclusive */
  293         umode_t i_mode;
  294 
  295         ret = -EINVAL;
  296         if (flags & ~VALID_FLAGS)
  297                 goto out;
  298 
  299         endbyte = offset + nbytes;
  300 
  301         if ((s64)offset < 0)
  302                 goto out;
  303         if ((s64)endbyte < 0)
  304                 goto out;
  305         if (endbyte < offset)
  306                 goto out;
  307 
  308         if (sizeof(pgoff_t) == 4) {
  309                 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
  310                         /*
  311                          * The range starts outside a 32 bit machine's
  312                          * pagecache addressing capabilities.  Let it "succeed"
  313                          */
  314                         ret = 0;
  315                         goto out;
  316                 }
  317                 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
  318                         /*
  319                          * Out to EOF
  320                          */
  321                         nbytes = 0;
  322                 }
  323         }
  324 
  325         if (nbytes == 0)
  326                 endbyte = LLONG_MAX;
  327         else
  328                 endbyte--;              /* inclusive */
  329 
  330         ret = -EBADF;
  331         f = fdget(fd);
  332         if (!f.file)
  333                 goto out;
  334 
  335         i_mode = f.file->f_path.dentry->d_inode->i_mode;
  336         ret = -ESPIPE;
  337         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
  338                         !S_ISLNK(i_mode))
  339                 goto out_put;
  340 
  341         mapping = f.file->f_mapping;
  342         if (!mapping) {
  343                 ret = -EINVAL;
  344                 goto out_put;
  345         }
  346 
  347         ret = 0;
  348         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
  349                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
  350                 if (ret < 0)
  351                         goto out_put;
  352         }
  353 
  354         if (flags & SYNC_FILE_RANGE_WRITE) {
  355                 ret = filemap_fdatawrite_range(mapping, offset, endbyte);
  356                 if (ret < 0)
  357                         goto out_put;
  358         }
  359 
  360         if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
  361                 ret = filemap_fdatawait_range(mapping, offset, endbyte);
  362 
  363 out_put:
  364         fdput(f);
  365 out:
  366         return ret;
  367 }
  368 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
  369 asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
  370                                     long flags)
  371 {
  372         return SYSC_sync_file_range((int) fd, offset, nbytes,
  373                                     (unsigned int) flags);
  374 }
  375 SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
  376 #endif
  377 
  378 /* It would be nice if people remember that not all the world's an i386
  379    when they introduce new system calls */
  380 SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
  381                                  loff_t offset, loff_t nbytes)
  382 {
  383         return sys_sync_file_range(fd, offset, nbytes, flags);
  384 }
  385 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
  386 asmlinkage long SyS_sync_file_range2(long fd, long flags,
  387                                      loff_t offset, loff_t nbytes)
  388 {
  389         return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
  390                                      offset, nbytes);
  391 }
  392 SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
  393 #endif

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