linux-kernel - Re: [PATCH AUTOSEL 5.10 5/7] cifs: add a warning when the in-flight count goes negative

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Message-ID: <ZPUmSbkrb4sYcrpq@sashalap>
Date:   Sun, 3 Sep 2023 20:35:21 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Shyam Prasad N <sprasad@...rosoft.com>,
        Bharath SM <bharathsm@...rosoft.com>,
        Steve French <stfrench@...rosoft.com>, pc@....nz,
        lsahlber@...hat.com, pc@...guebit.com, vl@...ba.org,
        ematsumiya@...e.de
Subject: Re: [PATCH AUTOSEL 5.10 5/7] cifs: add a warning when the in-flight
 count goes negative

On Tue, Aug 29, 2023 at 03:47:28PM +0200, Greg KH wrote:
>On Tue, Aug 29, 2023 at 09:33:34AM -0400, Sasha Levin wrote:
>> From: Shyam Prasad N <sprasad@...rosoft.com>
>>
>> [ Upstream commit e4645cc2f1e2d6f268bb8dcfac40997c52432aed ]
>>
>> We've seen the in-flight count go into negative with some
>> internal stress testing in Microsoft.
>>
>> Adding a WARN when this happens, in hope of understanding
>> why this happens when it happens.
>>
>> Signed-off-by: Shyam Prasad N <sprasad@...rosoft.com>
>> Reviewed-by: Bharath SM <bharathsm@...rosoft.com>
>> Signed-off-by: Steve French <stfrench@...rosoft.com>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  fs/cifs/smb2ops.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
>> index 015b7b37edee5..7ed6c2d4c549a 100644
>> --- a/fs/cifs/smb2ops.c
>> +++ b/fs/cifs/smb2ops.c
>> @@ -82,6 +82,7 @@ smb2_add_credits(struct TCP_Server_Info *server,
>>  		*val = 65000; /* Don't get near 64K credits, avoid srv bugs */
>>  		pr_warn_once("server overflowed SMB3 credits\n");
>>  	}
>> +	WARN_ON_ONCE(server->in_flight == 0);
>>  	server->in_flight--;
>>  	if (server->in_flight == 0 && (optype & CIFS_OP_MASK) != CIFS_NEG_OP)
>>  		rc = change_conf(server);
>> --
>> 2.40.1
>>
>
>Please drop this from all queues, it's debugging code for the CIFS
>developers, and they can debug it in Linus's tree, not in the stable
>trees where something like this is going to cause systems to reboot.

Dropped, thanks!

-- 
Thanks,
Sasha