linux-kernel - Re: [PATCH] overlayfs: set ctime when setting mtime and atime

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Message-ID: <CAOQ4uxhYRnX0NChCU2tsEi7eUPqbqQDeOwQT4ubWUgtCN0OVfA@mail.gmail.com>
Date:   Wed, 13 Sep 2023 20:36:45 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Miklos Szeredi <miklos@...redi.hu>,
        Nathan Chancellor <nathan@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-unionfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] overlayfs: set ctime when setting mtime and atime

On Wed, Sep 13, 2023 at 4:33 PM Jeff Layton <jlayton@...nel.org> wrote:
>
> Nathan reported that he was seeing the new warning in
> setattr_copy_mgtime pop when starting podman containers. Overlayfs is
> trying to set the atime and mtime via notify_change without also
> setting the ctime.
>
> POSIX states that when the atime and mtime are updated via utimes() that
> we must also update the ctime to the current time. The situation with
> overlayfs copy-up is analogous, so add ATTR_CTIME to the bitmask.
> notify_change will fill in the value.
>

IDGI, if ctime always needs to be set along with ATIME / MTIME, why not
let notify_change() set the bit instead of assert and fix all the callers?
But maybe I am missing something.

Anyway, I have no objection to the ovl patch.
It's fine by me if Christian applies it to the vfs.ctime branch with my ACK.

Thanks,
Amir.

> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
> The new WARN_ON_ONCE in setattr_copy_mgtime caught a bug! Fix up
> overlayfs to ensure that the ctime on the upper inode is also updated
> when copying up the atime and mtime.
> ---
>  fs/overlayfs/copy_up.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index d1761ec5866a..ada3fcc9c6d5 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -337,7 +337,7 @@ static int ovl_set_timestamps(struct ovl_fs *ofs, struct dentry *upperdentry,
>  {
>         struct iattr attr = {
>                 .ia_valid =
> -                    ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
> +                    ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_CTIME,
>                 .ia_atime = stat->atime,
>                 .ia_mtime = stat->mtime,
>         };
>
> ---
> base-commit: 9cb8e7c86ac793862e7bea7904b3426942bbd7ef
> change-id: 20230913-ctime-299173760dd9
>
> Best regards,
> --
> Jeff Layton <jlayton@...nel.org>
>