Re: [PATCH v3 3/3] ovl: do not set overlay.opaque for new directories

From: Amir Goldstein <amir73il@gmail.com>
To: Vyacheslav Yurkov <uvv.mail@gmail.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	Vyacheslav Yurkov <Vyacheslav.Yurkov@bruker.com>
Subject: Re: [PATCH v3 3/3] ovl: do not set overlay.opaque for new directories
Date: Fri, 28 May 2021 14:38:44 +0300	[thread overview]
Message-ID: <CAOQ4uxh7eSy6xAr9HdtZ=trcpUs8O5exXWJ8uqo2bacfMZXz3Q@mail.gmail.com> (raw)
In-Reply-To: <20210527174547.109269-3-uvv.mail@gmail.com>

On Thu, May 27, 2021 at 8:46 PM Vyacheslav Yurkov <uvv.mail@gmail.com> wrote:
>
> From: Vyacheslav Yurkov <Vyacheslav.Yurkov@bruker.com>
>
> Enable optimizations only if user opted-in for any of extended features.
> If optimization is enabled, it breaks existing use case when a lower layer
> directory appears after directory was created on a merged layer. If
> overlay.opaque is applied, new files on lower layer are not visible.
>
> Consider the following scenario:
> - /lower and /upper are mounted to /merged
> - directory /merged/new-dir is created with a file test1
> - overlay is unmounted
> - directory /lower/new-dir is created with a file test2
> - overlay is mounted again
>
> If opaque is applied by default, file test2 is not going to be visible
> without explicitly clearing the overlay.opaque attribute
>
> Signed-off-by: Vyacheslav Yurkov <Vyacheslav.Yurkov@bruker.com>
> ---

Vyacheslav,

The series looks good.
In case you post another version please add:
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

No need to repost just for that.

Did you happen to run xfstests on these patches?

If I am not mistaken, tests overlay/068 and overlay/069 provide
test coverage to the check in ovl_lower_uuid_ok() for the case
of lower null uuid (lower overlayfs) and user opt-in to new features
(nfs_export), so tests would have caught the bug you had in v2.

Please verify that I am not wrong (about test catching v2 bug) and
that v3 passes at least:
./check -overlay -g overlay/quick -g overlay/union

Please see README.overlay in xfstests for setting up to run
./check -overlay and the unionmount tests.

Thanks,
Amir.

>  fs/overlayfs/dir.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> index 93efe7048a77..03a22954fe61 100644
> --- a/fs/overlayfs/dir.c
> +++ b/fs/overlayfs/dir.c
> @@ -320,6 +320,7 @@ static bool ovl_type_origin(struct dentry *dentry)
>  static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
>                             struct ovl_cattr *attr)
>  {
> +       struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
>         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
>         struct inode *udir = upperdir->d_inode;
>         struct dentry *newdentry;
> @@ -338,7 +339,8 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
>         if (IS_ERR(newdentry))
>                 goto out_unlock;
>
> -       if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
> +       if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry) &&
> +           !ovl_allow_offline_changes(ofs)) {
>                 /* Setting opaque here is just an optimization, allow to fail */
>                 ovl_set_opaque(dentry, newdentry);
>         }
> --
> 2.25.1
>