From: NeilBrown <neilb@suse.de>
To: majianpeng <majianpeng@gmail.com>
Cc: shli <shli@kernel.org>, linux-raid <linux-raid@vger.kernel.org>,
axboe <axboe@kernel.dk>, Dan Williams <dan.j.williams@intel.com>
Subject: Re: [patch 03/10 v3] raid5: add a per-stripe lock
Date: Wed, 4 Jul 2012 09:56:24 +1000 [thread overview]
Message-ID: <20120704095624.7307c6cd@notabene.brown> (raw)
In-Reply-To: <201207032016270001820@gmail.com>
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On Tue, 3 Jul 2012 20:16:31 +0800 majianpeng <majianpeng@gmail.com> wrote:
> On 2012-07-02 15:39 NeilBrown <neilb@suse.de> Wrote:
> >On Mon, 2 Jul 2012 11:16:26 +0800 Shaohua Li <shli@kernel.org> wrote:
> >
> >
> >> > Then I could see what is being added and what is being removed all in the one
> >> > patch and I can be sure that they balance.
> >>
> >> reworked the patch 3-5 to two patches as you suggested, and sent to you. please check.
> >
> >Thanks. That's looking really good.
> >
> >However I think we can do better. I've been looking more closely at the code
> >and I think that the only things that we need stripe_lock to protect are
> >->toread and ->towrite, together with the following bios. e.g.
> >->toread->bi_next etc.
> >
> >->read and ->written don't need stripe_lock protection, as they are only
> >manipulated by the handle_stripe state machine which uses STRIPE_ACTIVE
> >and refcounts for exclusion.
> >
> >So add_stripe_bio need to take the lock while adding a bio to the
> >->toread and ->towrite lists, and ops_run_biodrain() and ops_run_biofill
> >need to take the lock while the move the list from ->to{read,write} to
> >->{read,written}.
> How about xchg()?
(it would help a little if you made your comments stand out more, and maybe
be a bit more verbose).
bio_add_stripe() can insert a new bio into a list that starts are ->towrite
or ->toread.
You cannot do that with a simple xchg. You really need a lock.
NeilBrown
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next prev parent reply other threads:[~2012-07-03 23:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-25 7:24 [patch 00/10 v3] raid5: improve write performance for fast storage Shaohua Li
2012-06-25 7:24 ` [patch 01/10 v3] raid5: use wake_up_all for overlap waking Shaohua Li
2012-06-28 7:26 ` NeilBrown
2012-06-28 8:53 ` Shaohua Li
2012-06-25 7:24 ` [patch 02/10 v3] raid5: delayed stripe fix Shaohua Li
2012-07-02 0:46 ` NeilBrown
2012-07-02 0:49 ` Shaohua Li
2012-07-02 0:55 ` NeilBrown
2012-06-25 7:24 ` [patch 03/10 v3] raid5: add a per-stripe lock Shaohua Li
2012-07-02 0:50 ` NeilBrown
2012-07-02 3:16 ` Shaohua Li
2012-07-02 7:39 ` NeilBrown
2012-07-03 1:27 ` Shaohua Li
2012-07-03 12:16 ` majianpeng
2012-07-03 23:56 ` NeilBrown [this message]
2012-07-04 1:09 ` majianpeng
2012-06-25 7:24 ` [patch 04/10 v3] raid5: lockless access raid5 overrided bi_phys_segments Shaohua Li
2012-06-25 7:24 ` [patch 05/10 v3] raid5: remove some device_lock locking places Shaohua Li
2012-06-25 7:24 ` [patch 06/10 v3] raid5: reduce chance release_stripe() taking device_lock Shaohua Li
2012-07-02 0:57 ` NeilBrown
2012-06-25 7:24 ` [patch 07/10 v3] md: personality can provide unplug private data Shaohua Li
2012-07-02 1:06 ` NeilBrown
2012-06-25 7:24 ` [patch 08/10 v3] raid5: make_request use batch stripe release Shaohua Li
2012-07-02 2:31 ` NeilBrown
2012-07-02 2:59 ` Shaohua Li
2012-07-02 5:07 ` NeilBrown
2012-06-25 7:24 ` [patch 09/10 v3] raid5: raid5d handle stripe in batch way Shaohua Li
2012-07-02 2:32 ` NeilBrown
2012-06-25 7:24 ` [patch 10/10 v3] raid5: create multiple threads to handle stripes Shaohua Li
2012-07-02 2:39 ` NeilBrown
2012-07-02 20:03 ` Dan Williams
2012-07-03 8:04 ` Shaohua Li
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