linux-kernel - Re: [PATCH v1 4/9] blk-mq: introduce init_flush_rq_fn callback in 'blk_mq

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]

Message-ID: <53F0F6CA.5010508@kernel.dk>
Date:	Sun, 17 Aug 2014 12:39:06 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Ming Lei <ming.lei@...onical.com>
CC:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Kleikamp <dave.kleikamp@...cle.com>,
	Zach Brown <zab@...bo.net>, Benjamin LaHaise <bcrl@...ck.org>,
	Christoph Hellwig <hch@...radead.org>,
	Kent Overstreet <kmo@...erainc.com>, linux-aio@...ck.org,
	linux-fsdevel@...r.kernel.org, Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH v1 4/9] blk-mq: introduce init_flush_rq_fn callback in
 'blk_mq_ops'

On 2014-08-16 01:49, Ming Lei wrote:
> On 8/16/14, Jens Axboe <axboe@...nel.dk> wrote:
>> On 08/14/2014 09:50 AM, Ming Lei wrote:
>>> Currently pdu of the flush rq is simlpy copied from another rq,
>>> it isn't enough to initialize pointer field well, so introduce
>>> the callback for driver to handle the case easily.
>>
>> This is the only patch I don't really like. Can't we make do with
>> calling ->init_request() for this instead of having to add another
>> (weird) hook?
>
> I considered ->init_request() before, but looks there are some problems:
>
> - from API view, both 'hctx_idx' and 'request_idx' parameter don't make
> sense for flush rq since it beongs to request queue instead of any one
> of hctx
>
> - init_request()/exit_request() are weird too, since they will be called
> for queuing every flush req, and they should have been called one
> shot
>
> - it is called before queuing each flush req, and might introduce a bit cost
> unnecessarily if init_request does lots of stuff
>
> - using init_request may break some current drivers(like scsi)
>
> Now I feel ->init_flush_rq() isn't good too, how about introducing
> prepare_flush_rq() and unprepare_flush_rq()? And they can be
> lightweight and have document benefit at least.

I think that's a better approach, lets do that.

-- 
Jens Axboe

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/