Re: Multichannel patches

From: Shyam Prasad N <nspmangalore@gmail.com>
To: Paulo Alcantara <pc@cjr.nz>
Cc: "Steve French" <smfrench@gmail.com>,
	"Aurélien Aptel" <aaptel@suse.com>,
	CIFS <linux-cifs@vger.kernel.org>,
	sribhat.msa@outlook.com, "rohiths msft" <rohiths.msft@gmail.com>
Subject: Re: Multichannel patches
Date: Sat, 5 Jun 2021 19:38:12 +0530	[thread overview]
Message-ID: <CANT5p=ro-sZfc8bPhh7COEp_KBHF6KNzbSV30WyRo2NHLneqAw@mail.gmail.com> (raw)
In-Reply-To: <87y2bpk5xu.fsf@cjr.nz>

The buildbot testing once hit a deadlock when running with the above patches.
I found one possibility during cifs_reconnect, where a deadlock can occur.

I've fixed that and some warnings that kernel bots have identified in
the below two patches:
https://github.com/sprasad-microsoft/smb-kernel-client/pull/5/commits/f3e65f72b03b03bc4b301e8e04e9babb0e9582cf.patch
https://github.com/sprasad-microsoft/smb-kernel-client/pull/5/commits/7b3e867e994a7cbc88efe85c95167ae49d4b7a9d.patch

Regards,
Shyam

On Fri, Jun 4, 2021 at 8:55 PM Paulo Alcantara <pc@cjr.nz> wrote:
>
> Shyam Prasad N <nspmangalore@gmail.com> writes:
>
> > @Paulo Alcantara That would be great if you can help testing my
> > changes. Please test with these new changes.
>
> OK.
>
> >> The super is only used for providing cifs_sb_info::origin_fullpath as key to find the corresponding failover targets in referral cache.
> > I'm wondering what would happen if there are multiple tcons to the
> > same origin_fullpath (possibly in different sessions)?
>
> That is certainly a problem, indeed.  I'm waiting for the DFS tests to
> finish and then send a series that contains a potential fix for that --
> e.g. not sharing TCP servers when mounting DFS shares.  We used to not
> share tcons with DFS mounts because they might contain different prefix
> paths but connected to same share, however that wasn't enough because
> multiple DFS mounts may connect to same target servers, although they
> might failover to completely different servers.
>
> > Also, doesn't failover targets apply to each channel under a session?
> > Shouldn't we switch targets on reconnect of secondary channels too?
>
> That's a interesting question.  I recall discussing this with Aurelien
> some time ago while running a few DFS + multichannel tests.
>
> So yes, I agree with you that when we successfully reconnect to failover
> target (primary channel), then we should also update all secondary
> channels with the new server's ip address and reconnect them.

-- 
Regards,
Shyam