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filesystem freeze: implement generic freeze feature

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The ioctls for the generic freeze feature are below.
o Freeze the filesystem
  int ioctl(int fd, int FIFREEZE, arg)
    fd: The file descriptor of the mountpoint
    FIFREEZE: request code for the freeze
    arg: Ignored
    Return value: 0 if the operation succeeds. Otherwise, -1

o Unfreeze the filesystem
  int ioctl(int fd, int FITHAW, arg)
    fd: The file descriptor of the mountpoint
    FITHAW: request code for unfreeze
    arg: Ignored
    Return value: 0 if the operation succeeds. Otherwise, -1
    Error number: If the filesystem has already been unfrozen,
                  errno is set to EINVAL.

[akpm@linux-foundation.org: fix CONFIG_BLOCK=n]
Signed-off-by: Takashi Sato <t-sato@yk.jp.nec.com>
Signed-off-by: Masayuki Hamaguchi <m-hamaguchi@ys.jp.nec.com>
Cc: <xfs-masters@oss.sgi.com>
Cc: <linux-ext4@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Kleikamp <shaggy@austin.ibm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Takashi Sato
2009-01-09 16:40:59 -08:00
committed by Linus Torvalds
parent c4be0c1dc4
commit fcccf50254
5 changed files with 130 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/buffer.c
+65 -9
View File
@@ -203,10 +203,25 @@ int fsync_bdev(struct block_device *bdev)
* happen on bdev until thaw_bdev() is called.
* If a superblock is found on this device, we take the s_umount semaphore
* on it to make sure nobody unmounts until the snapshot creation is done.
* The reference counter (bd_fsfreeze_count) guarantees that only the last
* unfreeze process can unfreeze the frozen filesystem actually when multiple
* freeze requests arrive simultaneously. It counts up in freeze_bdev() and
* count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
* actually.
*/
struct super_block *freeze_bdev(struct block_device *bdev)
{
struct super_block *sb;
int error = 0;
mutex_lock(&bdev->bd_fsfreeze_mutex);
if (bdev->bd_fsfreeze_count > 0) {
bdev->bd_fsfreeze_count++;
sb = get_super(bdev);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return sb;
}
bdev->bd_fsfreeze_count++;
down(&bdev->bd_mount_sem);
sb = get_super(bdev);
@@ -221,11 +236,24 @@ struct super_block *freeze_bdev(struct block_device *bdev)
sync_blockdev(sb->s_bdev);
if (sb->s_op->freeze_fs)
sb->s_op->freeze_fs(sb);
if (sb->s_op->freeze_fs) {
error = sb->s_op->freeze_fs(sb);
if (error) {
printk(KERN_ERR
"VFS:Filesystem freeze failed\n");
sb->s_frozen = SB_UNFROZEN;
drop_super(sb);
up(&bdev->bd_mount_sem);
bdev->bd_fsfreeze_count--;
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return ERR_PTR(error);
}
}
}
sync_blockdev(bdev);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
}
EXPORT_SYMBOL(freeze_bdev);
@@ -237,20 +265,48 @@ EXPORT_SYMBOL(freeze_bdev);
*
* Unlocks the filesystem and marks it writeable again after freeze_bdev().
*/
void thaw_bdev(struct block_device *bdev, struct super_block *sb)
int thaw_bdev(struct block_device *bdev, struct super_block *sb)
{
int error = 0;
mutex_lock(&bdev->bd_fsfreeze_mutex);
if (!bdev->bd_fsfreeze_count) {
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return -EINVAL;
}
bdev->bd_fsfreeze_count--;
if (bdev->bd_fsfreeze_count > 0) {
if (sb)
drop_super(sb);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return 0;
}
if (sb) {
BUG_ON(sb->s_bdev != bdev);
if (sb->s_op->unfreeze_fs)
sb->s_op->unfreeze_fs(sb);
sb->s_frozen = SB_UNFROZEN;
smp_wmb();
wake_up(&sb->s_wait_unfrozen);
if (!(sb->s_flags & MS_RDONLY)) {
if (sb->s_op->unfreeze_fs) {
error = sb->s_op->unfreeze_fs(sb);
if (error) {
printk(KERN_ERR
"VFS:Filesystem thaw failed\n");
sb->s_frozen = SB_FREEZE_TRANS;
bdev->bd_fsfreeze_count++;
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return error;
}
}
sb->s_frozen = SB_UNFROZEN;
smp_wmb();
wake_up(&sb->s_wait_unfrozen);
}
drop_super(sb);
}
up(&bdev->bd_mount_sem);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return 0;
}
EXPORT_SYMBOL(thaw_bdev);