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From:   Steve French <smfrench@gmail.com>
Date:   Thu, 16 Nov 2023 13:10:58 -0600
Message-ID: <CAH2r5mu8NBbW3ipMYd-UdfV+oDA1R7mwV-A8=PzU5qrd4kEiGg@mail.gmail.com>
Subject: [PATCH][SMB client] two multichannel patches
To:     CIFS <linux-cifs@vger.kernel.org>,
        samba-technical <samba-technical@lists.samba.org>
Cc:     LKML <linux-kernel@vger.kernel.org>
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Any thoughts on these two multichannel patches from Shyam (attached)?

The first fixes: "cifs: account for primary channel in the interface
list" which fixes a refcounting issue in channel deallocation.  The
second fixes a lock ordering problem in the recent patch: "cifs:
handle when server stops supporting multichannel"

The code to handle the case of server disabling multichannel
was picking iface_lock with chan_lock held. This goes against
the lock ordering rules, as iface_lock is a higher order lock
(even if it isn't so obvious).

This change fixes the lock ordering by doing the following in
that order for each secondary channel:
1. store iface and server pointers in local variable
2. remove references to iface and server in channels
3. unlock chan_lock
4. lock iface_lock
5. dec ref count for iface
6. unlock iface_lock
7. dec ref count for server
8. lock chan_lock again

Let me know if any test feedback or reviews

-- 
Thanks,

Steve

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