From: Shaohua Li <shli@kernel.org>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Vivek Goyal <vgoyal@redhat.com>,
axboe@kernel.dk, linux-kernel@vger.kernel.org, neilb@suse.de
Subject: Re: [patch 1/2]block: handle merged discard request
Date: Thu, 22 Mar 2012 10:39:19 +0800 [thread overview]
Message-ID: <CANejiEX26=jqijgTwb0iLMw7WC7byF1o+whwp3K5CcY5_a8o8w@mail.gmail.com> (raw)
In-Reply-To: <yq18vitwejt.fsf@sermon.lab.mkp.net>
2012/3/22 Martin K. Petersen <martin.petersen@oracle.com>:
>>>>>> "Shaohua" == Shaohua Li <shli@kernel.org> writes:
>
> Shaohua> The SCSI discard implementation hacks the first bio of request
> Shaohua> to add payload, which makes blk_update_request() can't
> Shaohua> correctly mark bios finish. The patch solves it. We set
> Shaohua> discard bio size to 0 and finish it after the hacked payload
> Shaohua> finishes.
>
> Ick!
>
> Also, you can't muck with bi_size because if we get an I/O error and
> have to reissue the command we no longer know how much to write.
> I have had to deal with the same issue for WRITE SAME. And the only sane
> approach is to distinguish between the DMA transfer size and the blocks
> "affected" by the command. That's what I'm working on right now for copy
> offload...
Yes, this is a problem. But note we already have this problem with
discard request for a long time. The payload has just (sector, length).
And looks the request finish returns the transfered data of the
payload instead of the discarded data. Am I missing anything?
> If this is something you want in 3.4 I guess we could temporarily add a
> separate length field to struct request. If you can wait I suggest we
> talk at LSF.
This blocked my raid discard patches, but I can wait. Sure we can have
a talk at LSF.
Thanks,
Shaohua
next prev parent reply other threads:[~2012-03-22 2:39 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-16 7:32 [patch v2 0/6] Add TRIM support for raid linear/0/1/10 Shaohua Li
2012-03-16 7:32 ` [patch v2 1/6] block: makes bio_split support bio without data Shaohua Li
2012-03-16 7:32 ` [patch v2 2/6] blk: dont allow discard request merge temporarily Shaohua Li
2012-03-20 16:21 ` Vivek Goyal
2012-03-21 1:22 ` Shaohua Li
2012-03-21 12:14 ` [patch 1/2]block: handle merged discard request Shaohua Li
2012-03-22 2:32 ` Martin K. Petersen
2012-03-22 2:39 ` Shaohua Li [this message]
2012-03-22 2:53 ` Martin K. Petersen
2012-06-20 8:57 ` Christoph Hellwig
2012-06-22 3:46 ` Martin K. Petersen
2012-08-03 2:10 ` Shaohua Li
2012-08-18 3:06 ` Mike Snitzer
2012-08-18 3:47 ` Martin K. Petersen
2012-08-20 13:57 ` Mike Snitzer
2012-08-20 13:58 ` Christoph Hellwig
2012-08-20 14:12 ` Mike Snitzer
2012-08-20 14:15 ` Christoph Hellwig
2012-03-22 2:18 ` [patch v2 2/6] blk: dont allow discard request merge temporarily Martin K. Petersen
2012-03-22 2:33 ` Shaohua Li
2012-03-22 6:28 ` Christoph Hellwig
2012-03-16 7:32 ` [patch v2 3/6] md: linear supports TRIM Shaohua Li
2012-03-16 7:32 ` [patch v2 4/6] md: raid 0 " Shaohua Li
2012-03-16 7:32 ` [patch v2 5/6] md: raid 1 " Shaohua Li
2012-03-16 7:32 ` [patch v2 6/6] md: raid 10 " Shaohua Li
2012-03-19 19:38 ` [patch v2 0/6] Add TRIM support for raid linear/0/1/10 Holger Kiehl
2012-03-20 1:27 ` Shaohua Li
2012-03-20 9:50 ` Holger Kiehl
2012-03-20 12:09 ` Shaohua Li
2012-03-21 2:08 ` Shaohua Li
2012-03-21 2:24 ` Roberto Spadim
2012-03-21 2:29 ` Mathias Burén
2012-03-21 2:29 ` Mathias Burén
2012-05-08 9:59 ` Patelczyk, Maciej
2012-05-09 2:27 ` Shaohua Li
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