[Cluster-devel] [PATCH] gfs2: fix race between gfs2_freeze_func and unmount

[Abhijith Das <adas@redhat.com>]

NACK. Andreas mentioned that the description could be more descriptive and
that we should be using clear_bit_unlock() instead of clear_bit(). I'll
post a v2 shortly with these changes.

Cheers!
--Abhi

On Tue, Apr 30, 2019 at 12:48 PM Abhi Das <adas@redhat.com> wrote:

> gfs2_unfreee() doesn't wait for gfs2_freeze_func() to complete. If a
> umount is issued right after unfreeze, it could result in an
> inconsistent filesystem because some journal data (statfs update)
> wasn't written out.
>
> This patch causes gfs2_unfreeze() to wait for gfs2_freeze_func() to
> complete before returning to the user.
>
> Signed-off-by: Abhi Das <adas@redhat.com>
> ---
>  fs/gfs2/incore.h | 1 +
>  fs/gfs2/super.c  | 8 +++++---
>  2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
> index 78c8e761b321..b15755068593 100644
> --- a/fs/gfs2/incore.h
> +++ b/fs/gfs2/incore.h
> @@ -621,6 +621,7 @@ enum {
>         SDF_SKIP_DLM_UNLOCK     = 8,
>         SDF_FORCE_AIL_FLUSH     = 9,
>         SDF_AIL1_IO_ERROR       = 10,
> +       SDF_FS_FROZEN           = 11,
>  };
>
>  enum gfs2_freeze_state {
> diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
> index a6a325b2a78b..a81d7a5afe39 100644
> --- a/fs/gfs2/super.c
> +++ b/fs/gfs2/super.c
> @@ -973,8 +973,7 @@ void gfs2_freeze_func(struct work_struct *work)
>         if (error) {
>                 printk(KERN_INFO "GFS2: couldn't get freeze lock : %d\n",
> error);
>                 gfs2_assert_withdraw(sdp, 0);
> -       }
> -       else {
> +       } else {
>                 atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
>                 error = thaw_super(sb);
>                 if (error) {
> @@ -987,6 +986,8 @@ void gfs2_freeze_func(struct work_struct *work)
>                 gfs2_glock_dq_uninit(&freeze_gh);
>         }
>         deactivate_super(sb);
> +       clear_bit(SDF_FS_FROZEN, &sdp->sd_flags);
> +       wake_up_bit(&sdp->sd_flags, SDF_FS_FROZEN);
>         return;
>  }
>
> @@ -1029,6 +1030,7 @@ static int gfs2_freeze(struct super_block *sb)
>                 msleep(1000);
>         }
>         error = 0;
> +       set_bit(SDF_FS_FROZEN, &sdp->sd_flags);
>  out:
>         mutex_unlock(&sdp->sd_freeze_mutex);
>         return error;
> @@ -1053,7 +1055,7 @@ static int gfs2_unfreeze(struct super_block *sb)
>
>         gfs2_glock_dq_uninit(&sdp->sd_freeze_gh);
>         mutex_unlock(&sdp->sd_freeze_mutex);
> -       return 0;
> +       return wait_on_bit(&sdp->sd_flags, SDF_FS_FROZEN,
> TASK_INTERRUPTIBLE);
>  }
>
>  /**
> --
> 2.20.1
>
>
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