linux-kernel - Re: [PATCH V2] scsi: core: use blk_mq_requeue_request in __scsi_queue

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Fri, 2 Mar 2018 10:17:24 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     Bart Van Assche <Bart.VanAssche@....com>,
        "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@....de" <hch@....de>
Subject: Re: [PATCH V2] scsi: core: use blk_mq_requeue_request in
 __scsi_queue_insert

Hi martin

Thanks for your kindly response.

On 03/02/2018 09:43 AM, Martin K. Petersen wrote:
> 
> Jianchao,
> 
>> Yes, the block layer core guarantees that scsi_mq_get_budget() will be
>> called before scsi_queue_rq(). I think the full picture is as follows:
> 
>> * Before scsi_queue_rq() calls .queuecommand(), get_device() is called for the
>>   SCSI device and the device, target and host busy counters are incremented.
>> * If the SCSI core decides to requeue a command, scsi_queue_insert() causes
>>   __scsi_queue_insert() to call scsi_device_unbusy(). That last function
>>   decreases the device, target and host busy counters but not put_device(sdev).
>>   Hence the need for a separate put_device() call after requeuing.
>>
>> It's unfortunate that the SCSI core became so asymmetric. Anyway,
>> since I am now convinced that this patch is correct, feel free to add:
> 
> Please add something akin to Bart's explanation as a comment and repost.

yes, sure.


Thanks
Jianchao