From: NeilBrown <neilb@suse.de>
To: Shaohua Li <shli@kernel.org>
Cc: linux-raid@vger.kernel.org, axboe@kernel.dk,
dan.j.williams@intel.com, shli@fusionio.com
Subject: Re: [patch 02/10 v3] raid5: delayed stripe fix
Date: Mon, 2 Jul 2012 10:55:37 +1000 [thread overview]
Message-ID: <20120702105537.24b86ced@notabene.brown> (raw)
In-Reply-To: <20120702004955.GA327@kernel.org>
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On Mon, 2 Jul 2012 08:49:55 +0800 Shaohua Li <shli@kernel.org> wrote:
> On Mon, Jul 02, 2012 at 10:46:48AM +1000, NeilBrown wrote:
> > On Mon, 25 Jun 2012 15:24:49 +0800 Shaohua Li <shli@kernel.org> wrote:
> >
> > > There isn't locking setting STRIPE_DELAYED and STRIPE_PREREAD_ACTIVE bits, but
> > > the two bits have relationship. A delayed stripe can be moved to hold list only
> > > when preread active stripe count is below IO_THRESHOLD. If a stripe has both
> > > the bits set, such stripe will be in delayed list and preread count not 0,
> > > which will make such stripe never leave delayed list.
> > >
> > > Signed-off-by: Shaohua Li <shli@fusionio.com>
> > > ---
> > > drivers/md/raid5.c | 4 +++-
> > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > Index: linux/drivers/md/raid5.c
> > > ===================================================================
> > > --- linux.orig/drivers/md/raid5.c 2012-06-25 14:36:15.964613183 +0800
> > > +++ linux/drivers/md/raid5.c 2012-06-25 14:36:57.280096788 +0800
> > > @@ -196,12 +196,14 @@ static void __release_stripe(struct r5co
> > > BUG_ON(!list_empty(&sh->lru));
> > > BUG_ON(atomic_read(&conf->active_stripes)==0);
> > > if (test_bit(STRIPE_HANDLE, &sh->state)) {
> > > - if (test_bit(STRIPE_DELAYED, &sh->state))
> > > + if (test_bit(STRIPE_DELAYED, &sh->state) &&
> > > + !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
> > > list_add_tail(&sh->lru, &conf->delayed_list);
> > > else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
> > > sh->bm_seq - conf->seq_write > 0)
> > > list_add_tail(&sh->lru, &conf->bitmap_list);
> > > else {
> > > + clear_bit(STRIPE_DELAYED, &sh->state);
> > > clear_bit(STRIPE_BIT_DELAY, &sh->state);
> > > list_add_tail(&sh->lru, &conf->handle_list);
> > > }
> >
> > Thanks. I've applied this patch and will submit it upstream shortly.
> >
> > Have you actually seen a stripe get trapped with both bits set, or is this
> > just a theoretical problem discovered by code inspection?
>
> I print the flags of strip when there is overlap sleep in make_request(), and
> found this case, so this is real.
OK, thanks.
>
> How do you think about the other patches in the series?
I'll let you know shortly.
NeilBrown
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next prev parent reply other threads:[~2012-07-02 0:55 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 [this message]
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
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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