Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
IronPort-SDR: pF4pWISwS0L3dcWNKzX9Wc8ozFT1OVtCUkZrUbLHAfenyGMI3yuoZR50P/lmy5gyYjOtydVT58
 y3EUFuMzSxfXjkvqIf7Y7VUdcsBACR0vVI4wr+ZJshdIq4s/HLq8KXKxyIcDSk2nxhMO/UhmQY
 FdaY2VQyPokpHPUWuTW+gFyGjjE1AKMqHpfn2IyH1G0gQrWCxxWgLDfQNIK4mhL9pIBr0mYWGg
 aH6UNwSj9ttoL1WLaenIWOHKSXKYlnvA5/dj8Aoq91HcKEgK95d6fHTr2jKQtlNUId4smqGqwN
 TDzWOaxTGhkRxuhCH1zhbCAu
IronPort-SDR: U1HA0pqg8spb0ksYPM47b2nrmxWWC61UVYHPKmRraKtc243n7BofHa1LeyWnzgf31+6sxU+PJX
 m5DnRQoa+7qZdCEkWt0PYtTB/A11lCd8P6//ZByGx5V6CnwHSWmzb6SCULzBFmxq+3dayScVB5
 LEbv4dx7nMiluBTey3LQBnW3T7+SFO4IhdExShFzxGpSO6fKt+qO2DSTp6FvJ8aGGI4NTiHpg0
 XAhqWgTSuZ8wwv8wcbG1znCm7iRZOdGEnJJlrfkQbmt6TQfBYoD58BGJIIXxxwiRmKWaQY+eMT
 LSw=
WDCIronportException: Internal
Message-ID: <ba090f1b-a767-46a1-5728-82d9c587ef3c@opensource.wdc.com>
Date:   Thu, 31 Mar 2022 07:30:35 +0900
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.7.0
Subject: Re: filesystem corruption with "scsi: core: Reallocate device's
 budget map on queue depth change"
Content-Language: en-US
To:     Ming Lei <ming.lei@redhat.com>,
        James Bottomley <jejb@linux.ibm.com>
Cc:     John Garry <john.garry@huawei.com>,
        Andrea Righi <andrea.righi@canonical.com>,
        Martin Wilck <martin.wilck@suse.com>,
        Bart Van Assche <bvanassche@acm.org>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
References: <YkQsumJ3lgGsagd2@arighi-desktop>
 <f7bacce8-b5e5-3ef1-e116-584c01533f69@huawei.com>
 <YkQ9KoKb+VK06zXi@arighi-desktop>
 <08717833-19bb-8aaa-4f24-2989a9f56cd3@huawei.com>
 <263108383b1c01cf9237ff2fcd2e97a482eff83e.camel@linux.ibm.com>
 <YkRfrjgNpD+S2WpN@T590>
From:   Damien Le Moal <damien.lemoal@opensource.wdc.com>
Organization: Western Digital Research
In-Reply-To: <YkRfrjgNpD+S2WpN@T590>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 3/30/22 22:48, Ming Lei wrote:
> On Wed, Mar 30, 2022 at 09:31:35AM -0400, James Bottomley wrote:
>> On Wed, 2022-03-30 at 13:59 +0100, John Garry wrote:
>>> On 30/03/2022 12:21, Andrea Righi wrote:
>>>> On Wed, Mar 30, 2022 at 11:38:02AM +0100, John Garry wrote:
>>>>> On 30/03/2022 11:11, Andrea Righi wrote:
>>>>>> Hello,
>>>>>>
>>>>>> after this commit I'm experiencing some filesystem corruptions
>>>>>> at boot on a power9 box with an aacraid controller.
>>>>>>
>>>>>> At the moment I'm running a 5.15.30 kernel; when the filesystem
>>>>>> is mounted at boot I see the following errors in the console:
>>>
>>> About "scsi: core: Reallocate device's budget map on queue depth
>>> change" being added to a stable kernel, I am not sure if this was
>>> really a fix  or just a memory optimisation.
>>
>> I can see how it becomes the problem: it frees and allocates a new
>> bitmap across a queue freeze, but bits in the old one might still be in
>> use.  This isn't a problem except when they return and we now possibly
>> see a tag greater than we think we can allocate coming back. 
>> Presumably we don't check this and we end up doing a write to
>> unallocated memory.
>>
>> I think if you want to reallocate on queue depth reduction, you might
>> have to drain the queue as well as freeze it.
> 
> After queue is frozen, there can't be any in-flight request/scsi
> command, so the sbitmap is zeroed at that time, and safe to reallocate.
> 
> The problem is aacraid specific, since the driver has hard limit
> of 256 queue depth, see aac_change_queue_depth().

256 is the scsi hard limit per device... Any SAS drive has the same limit
by default since there is no way to know the max queue depth of a scsi
disk. So what is special about aacraid ?

> 
> 
> Thanks,
> Ming
> 


-- 
Damien Le Moal
Western Digital Research