On Thu, Jan 19, 2017 at 2:13 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> freeze/thaw of upper is all that is needed.
>
Miklos,
Looking at it again, I believe that not even that is needed.
Having fixed ovl_sync_fs() with patch #2, ovl_freeze()
and ovl_unfreeze() need to be NOP. Am I right?
In fact, freezing upper fs, when many overlayfs mounts
share the same base fs (a-la docker) would be quite lame.
WRT other use cases of freezing overlayfs, I am not sure
if it is needed for correctness of docker checkpoint/restart?
Pavel?
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/super.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 6792bb7..0f8a9c8 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -160,6 +160,20 @@ static void ovl_put_super(struct super_block *sb)
> kfree(ufs);
> }
>
> +static int ovl_freeze(struct super_block *sb)
> +{
> + struct ovl_fs *ufs = sb->s_fs_info;
> +
> + return ufs->upper_mnt ? freeze_super(ufs->upper_mnt->mnt_sb) : 0;
> +}
> +
> +static int ovl_unfreeze(struct super_block *sb)
> +{
> + struct ovl_fs *ufs = sb->s_fs_info;
> +
> + return ufs->upper_mnt ? thaw_super(ufs->upper_mnt->mnt_sb) : 0;
> +}
> +
> /**
> * ovl_statfs
> * @sb: The overlayfs super block
> @@ -222,6 +236,8 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
>
> static const struct super_operations ovl_super_operations = {
> .put_super = ovl_put_super,
> + .freeze_fs = ovl_freeze,
> + .unfreeze_fs = ovl_unfreeze,
> .statfs = ovl_statfs,
> .show_options = ovl_show_options,
> .remount_fs = ovl_remount,
> --
> 2.7.4
>
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