linux-kernel - Re: [PATCH v2] cifs: Silently ignore unknown oplock break handle

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Message-ID: <93d506a6-5832-5006-3bab-6e8e7203da0e@talpey.com>
Date:   Tue, 16 Mar 2021 09:21:16 -0400
From:   Tom Talpey <tom@...pey.com>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Steve French <sfrench@...ba.org>
Cc:     linux-cifs@...r.kernel.org, kernel@...s.com,
        samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] cifs: Silently ignore unknown oplock break handle

On 3/16/2021 8:48 AM, Vincent Whitchurch via samba-technical wrote:
> Make SMB2 not print out an error when an oplock break is received for an
> unknown handle, similar to SMB1.  The SMB2 lease break path is not
> affected by this patch.
> 
> Without this, a program which writes to a file from one thread, and
> opens, reads, and writes the same file from another thread triggers the
> below errors several times a minute when run against a Samba server
> configured with "smb2 leases = no".
> 
>   CIFS: VFS: \\192.168.0.1 No task to wake, unknown frame received! NumMids 2
>   00000000: 424d53fe 00000040 00000000 00000012  .SMB@...........
>   00000010: 00000001 00000000 ffffffff ffffffff  ................
>   00000020: 00000000 00000000 00000000 00000000  ................
>   00000030: 00000000 00000000 00000000 00000000  ................
> 
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> ---
> 
> Notes:
>      v2:
>      - Drop change to lease break
>      - Rewrite commit message
> 
>   fs/cifs/smb2misc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
> index 60d4bd1eae2b..4d8576e202e3 100644
> --- a/fs/cifs/smb2misc.c
> +++ b/fs/cifs/smb2misc.c
> @@ -755,7 +755,7 @@ smb2_is_valid_oplock_break(char *buffer, struct TCP_Server_Info *server)
>   	}
>   	spin_unlock(&cifs_tcp_ses_lock);
>   	cifs_dbg(FYI, "Can not process oplock break for non-existent connection\n");
> -	return false;
> +	return true;
>   }
>   
>   void
> 

As an oplock-only approach, it looks good. But the old cifs_dbg message
"non-existent connection" is possibly misleading, since the connection
may be perfectly fine.

When breaking the loop successfully, the code emits
	cifs_dbg(FYI, "file id match, oplock break\n");
so perhaps
	cifs_dbg(FYI, "No file id matched, oplock break ignored\n");
?

Tom.