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Sender: Salvatore Bonaccorso <salvatore.bonaccorso@gmail.com>
Date:   Thu, 8 Apr 2021 13:41:05 +0200
From:   Salvatore Bonaccorso <carnil@debian.org>
To:     Shyam Prasad <Shyam.Prasad@microsoft.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Aurelien Aptel <aaptel@suse.com>,
        Steven French <Steven.French@microsoft.com>,
        Sasha Levin <sashal@kernel.org>
Subject: Re: [EXTERNAL] Re: [PATCH 4.19 013/247] cifs: Set
 CIFS_MOUNT_USE_PREFIX_PATH flag on setting cifs_sb->prepath.
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Hi Shyam,

On Tue, Apr 06, 2021 at 05:01:17PM +0200, Salvatore Bonaccorso wrote:
> Hi,
> 
> On Tue, Apr 06, 2021 at 02:00:48PM +0000, Shyam Prasad wrote:
> > Hi Greg,
> > We'll need to debug this further to understand what's going on. 
> 
> Greg asked it the same happens with 5.4 as well, I do not know I was
> not able to test 5.4.y (yet) but only 5.10.y and 4.19.y.
> > 
> > Hi Salvatore,
> > Any chance that you'll be able to provide us the cifsFYI logs from the time of mount failure?
> > https://wiki.samba.org/index.php/LinuxCIFS_troubleshooting#Enabling_Debugging
> 
> Please find it attached. Is this enough information?
> 
> The mentioned home DFS link 'home' is a DFS link to
> msdfs:SECONDHOST\REDACTED on a Samba host.
> 
> The mount is triggered as
> 
> mount -t cifs //HOSTIP/REDACTED/home /mnt --verbose -o username='REDACTED,domain=DOMAIN'

So I can confirm the issue is both present in 4.19.185 and 5.4.110
upstream (without any Debian patches applied, we do not anyway apply
any cifs related one on top of the respetive upstream version).

The issue is not present in 5.10.28.

So I think there are commits as dependency of a738c93fb1c1 ("cifs: Set
CIFS_MOUNT_USE_PREFIX_PATH flag on setting cifs_sb->prepath.") which
are required and not applied in the released before 5.10.y which make
introducing the regression.

Regards,
Salvatore