Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Paulo Alcantara <pc@cjr.nz>
To:     David Howells <dhowells@redhat.com>,
        Steve French <smfrench@gmail.com>
Cc:     dhowells@redhat.com, linux-nfs <linux-nfs@vger.kernel.org>,
        CIFS <linux-cifs@vger.kernel.org>, linux-afs@lists.infradead.org,
        ceph-devel@vger.kernel.org, keyrings@vger.kernel.org,
        Network Development <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, fweimer@redhat.com
Subject: Re: What's a good default TTL for DNS keys in the kernel
In-Reply-To: <927453.1587285472@warthog.procyon.org.uk>
References: <CAH2r5mv5p=WJQu2SbTn53FeTsXyN6ke_CgEjVARQ3fX8QAtK_w@mail.gmail.com>
 <3865908.1586874010@warthog.procyon.org.uk>
 <927453.1587285472@warthog.procyon.org.uk>
Date:   Sun, 19 Apr 2020 21:58:25 -0300
Message-ID: <87imhvj7m6.fsf@cjr.nz>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

David Howells <dhowells@redhat.com> writes:

> Steve French <smfrench@gmail.com> wrote:
>
>> For SMB3/CIFS mounts, Paulo added support last year for automatic
>> reconnect if the IP address of the server changes.  It also is helpful
>> when DFS (global name space) addresses change.
>
> What happens if the IP address the superblock is going to changes, then
> another mount is made back to the original IP address?  Does the second mount
> just pick the original superblock?

It is going to transparently reconnect to the new ip address, SMB share,
and cifs superblock is kept unchanged.  We, however, update internal
TCP_Server_Info structure to reflect new destination ip address.

For the second mount, since the hostname (extracted out of the UNC path
at mount time) resolves to a new ip address and that address was saved earlier
in TCP_Server_Info structure during reconnect, we will end up
reusing same cifs superblock as per fs/cifs/connect.c:cifs_match_super().