Re: [PATCH v3 2/4] ovl: relax WARN_ON() real inode attributes mismatch

[Vivek Goyal <vgoyal@redhat.com>]

On Tue, May 15, 2018 at 01:26:10PM +0300, Amir Goldstein wrote:
> Overlayfs should cope with online changes to underlying layer
> without crashing the kernel, which is what xfstest overlay/019
> checks.
> 
> This test may sometimes trigger WARN_ON() in ovl_create_or_link()
> when linking an overlay inode that has been changed on underlying
> layer.
> 
> Replace those WARN_ON() with pr_warn_ratelimited() to prevent
> test from failing and because this is more appropriate to the
> use case.
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/overlayfs/dir.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> index 62e6733b755c..25b339278684 100644
> --- a/fs/overlayfs/dir.c
> +++ b/fs/overlayfs/dir.c
> @@ -525,9 +525,17 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
>  	if (!err) {
>  		struct inode *realinode = d_inode(ovl_dentry_upper(dentry));
>  
> -		WARN_ON(inode->i_mode != realinode->i_mode);
> -		WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
> -		WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
> +		if (inode->i_mode != realinode->i_mode ||
> +		    !uid_eq(inode->i_uid, realinode->i_uid) ||
> +		    !gid_eq(inode->i_gid, realinode->i_gid)) {
> +			pr_warn_ratelimited("overlayfs: real inode attributes mismatch (%pd2, %o.%u.%u != %o.%u.%u).\n",
> +				dentry, inode->i_mode,
> +				from_kuid(&init_user_ns, inode->i_uid),
> +				from_kgid(&init_user_ns, inode->i_gid),
> +				realinode->i_mode,
> +				from_kuid(&init_user_ns, realinode->i_uid),
> +				from_kgid(&init_user_ns, realinode->i_gid));

Curious that why these calls to from_kuid() and from_kgid() was required
in this patch.

Vivek