linux-kernel - Re: [ata] 0568e61225: stress-ng.copy-file.ops_per

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 10 Aug 2022 06:52:03 -0700
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     John Garry <john.garry@...wei.com>,
        kernel test robot <oliver.sang@...el.com>
Cc:     Christoph Hellwig <hch@....de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-ide@...r.kernel.org, lkp@...ts.01.org, lkp@...el.com,
        ying.huang@...el.com, feng.tang@...el.com,
        zhengjun.xing@...ux.intel.com, fengwei.yin@...el.com
Subject: Re: [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0%
 regression

On 2022/08/10 1:33, John Garry wrote:
> On 09/08/2022 15:57, Damien Le Moal wrote:
>>>> As far as I can see, this patch should not make a difference unless the
>>>> ATA shost driver is setting the max_sectors value unnecessarily low.
>>> For __ATA_BASE_SHT, we don't set max_sectors. As such, we default
>>> shost->max_sectors = SCSI_DEFAULT_MAX_SECTORS (=1024) in
>>> scsi_host_alloc(). I assume no shost dma mapping limit applied.
>>>
>>> Then - for example - we could select dev->max_sectors =
>>> ATA_MAX_SECTORS_LBA48 (=65535) in ata_dev_configure().
>>>
>>> So with commit 0568e6122574 we would have final max sectors = 1024, as
>>> opposed to 65535 previously. I guess that the problem is something like
>>> this.
>>>
>>> If so, it seems that we would need to apply the shost dma mapping limit
>>> separately in ata_scsi_dev_config() and not use shost->max_sectors.
>> OK. Will have a look at that.
>>
> 
> We may need to introduce something like shost->max_hw_sectors, which is 
> set according to sht max sectors and dma mapping limits. That could be 
> also used in USB scsiglue slave_configure()
> 
> Or else set max_sectors value for __ATA_BASE_SHT, but I don't know a 
> sane value there considering ATA_MAX_SECTORS_LBA48 gives max_sectors of 
> 65535.
> 
> Damien, please let me know if you need help now. I am just waiting for 
> you to test to prove this theory about dev->max_sectors being capped. I 
> don't have an AHCI setup readily-available for testing - just SAS cards 
> or QEMU.

I am on it.

> 
> Thanks,
> John


-- 
Damien Le Moal
Western Digital Research