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

From: Amir Goldstein <amir73il@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Vivek Goyal <vgoyal@redhat.com>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v3 2/4] ovl: relax WARN_ON() real inode attributes mismatch
Date: Wed, 16 May 2018 14:06:20 +0300	[thread overview]
Message-ID: <CAOQ4uxiX3tNDV+aT1BFei4HReXybdTBgGQHGss1VOF5d0HX9VA@mail.gmail.com> (raw)
In-Reply-To: <CAJfpegs3AC6zTeHYmn0r9dNTHhf=jRpkkkyOegB+r=CDZCyk4w@mail.gmail.com>

On Wed, May 16, 2018 at 1:29 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Tue, May 15, 2018 at 12:26 PM, Amir Goldstein <amir73il@gmail.com> 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));
>> +               }
>
> How about just dropping the warnings altogether.  They didn't discover
> an issue with the code, just something normal, so IMO we should just
> get rid of them.
>

OK. On that subject, do you want to leave the 'debug' argument
to ovl_do_XXX? I started peeling it off slowly from the new helpers,
but maybe we should just yank it completely from the ovl_do_XXX
helpers? pr_debug can be disabled dynamically anyway. right?

Thanks,
Amir.