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

[Amir Goldstein <amir73il@gmail.com>]

On Tue, May 15, 2018 at 3:48 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
> 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.
>

kuid/kgid are opaque structs we should not access directly, so
I thought this was the standard way to get a value for printing.
Maybe I was wrong.

Thanks,
Amir.