On Thu, 21 Mar 2013 16:26:56 +0400, Dmitry Monakhov <dmonakhov@xxxxxxxxxx> wrote:
Ping... Please take a look at this fix.
> Commit: 18e9e5104fcd breaks connection between freeze_bdev()/thaw_bdev() and
> freeze_super()/thaw_super()
> In other workds:
> freeze_bdev()/thaw_bdev() may be called multiple times, but
> freeze_super()/thaw_super() only once (will resunt -EBUSY on second call)
>
> BUT user is still allowed to mix both interfaces:
>
> freeze_bdev () call it first time
> ->bdev->bd_fsfreeze_count++
> ->freeze_super()
> return 0
> freeze_super() second time
> ->bdev->bd_fsfreeze_count++
> return 0
>
> One can call ioctl_fsthaw( #xfs_freeze -u $MNT)
> ioctl_fsthaw
> ->thaw_super() -> fs is unfrozen now
> return 0
>
> This leave bdev in broken state because:
> bd_fsfreeze_count > 0 but superblock is not frozen.
> Visiable effect:
> 0) Any freeze_bdev() will not call freeze_super() because
> (bdev->bd_fsfreeze_count > 0)
> 1) thaw_bdev() will fail because thaw_super() will return EINVAL (filesystem
> is not frozen) and bdev->bd_fsfreeze_count will not being decremented.
> 2) filesystem may not being mounted because mount_bdev will fail
> because (bdev->bd_fsfreeze_count > 0)
>
> #TEST_CASE:
> # Use xfstests 068'th test
> (while true ;do dmsetup suspend $SCRATCH_DEV ;dmsetup resume $SCRATCH_DEV;done)&
> pid=$!
> ./check 068 068 068 068 068
> kill $pid
> wait $pid
>
> In order to fix that let's always use {freeze,thaw}_bdev() functions if
> super block has bdev, and directly call {freeze,thaw)_super() otherwise.
>
> Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> ---
> fs/ioctl.c | 16 +++++++++++++---
> 1 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 3bdad6d..ea47ccc 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -513,6 +513,7 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
> static int ioctl_fsfreeze(struct file *filp)
> {
> struct super_block *sb = filp->f_path.dentry->d_inode->i_sb;
> + int ret = 0;
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
> @@ -521,8 +522,15 @@ static int ioctl_fsfreeze(struct file *filp)
> if (sb->s_op->freeze_fs == NULL)
> return -EOPNOTSUPP;
>
> - /* Freeze */
> - return freeze_super(sb);
> + if (sb->s_bdev) {
> + struct super_block *fsb;
> + fsb = freeze_bdev(sb->s_bdev);
> + if (IS_ERR(fsb))
> + ret = PTR_ERR(fsb);
> + } else {
> + ret = freeze_super(sb);
> + }
> + return ret;
> }
>
> static int ioctl_fsthaw(struct file *filp)
> @@ -532,7 +540,9 @@ static int ioctl_fsthaw(struct file *filp)
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - /* Thaw */
> + if (sb->s_bdev)
> + return thaw_bdev(sb->s_bdev, sb);
> +
> return thaw_super(sb);
> }
>
> --
> 1.7.1
>
> --
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