On Sat, Sep 29, 2007 at 07:09:12PM +0900, Akinobu Mita wrote:
> freeze_bdev() with the device which is mounted as read only
> does not change sb->s_frozen from SB_UNFROZEN to SB_FREEZE_TRANS.
>
> Because of this behavior, xfs_freeze can break read-only XFS filesystem.
>
> Because xfs_thaw does nothing for the filesystem whose sb->s_frozen is
> SB_UNFROZEN. So freezed readonly XFS filesystem will never be unfreezed.
> Then we cannot do any unmount/remount operations for that filesystem.
>
> This patch updates sb->s_frozen when freeze_bdev() is called for read-only
> mounted device, too.
I think this fix is valid, but it might be a tad cleaner to just
set s_frozen to SB_FREEZE_TRANS directly in a separate branch, ala:
struct super_block *freeze_bdev(struct block_device *bdev)
{
struct super_block *sb;
down(&bdev->bd_mount_sem);
sb = get_super(bdev);
if (!sb)
goto out;
if (sb->s_flags & MS_RDONLY) {
sb->s_frozen = SB_FREEZE_TRANS;
smp_wmb();
goto out;
}
sb->s_frozen = SB_FREEZE_WRITE;
smp_wmb();
__fsync_super(sb);
sb->s_frozen = SB_FREEZE_TRANS
smp_wmb();
sync_blockdev(sb->s_bdev);
if (sb->s_op->write_super_lockfs)
sb->s_op->write_super_lockfs(sb);
out:
sync_blockdev(bdev);
return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
}
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