From: NeilBrown <neilb@suse.com>
To: Vaughan <cxt9401@163.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: How does md gurantee not miss to free an active stripe_head when md stops?
Date: Fri, 22 Jul 2016 11:15:47 +1000 [thread overview]
Message-ID: <871t2m8occ.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <004e01d1e274$faa33a20$efe9ae60$@163.com>
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On Wed, Jul 20 2016, Vaughan wrote:
> Hi Neil,
>
> I'm using v3.10 md code for develop. Recently I encounter a problem where an
> read IO usually returned from physical disk after md has been stopped.
> I reviewed the code and find when md stops, it unregister raid5d
> unconditionally and call shrink_stripes() to free only the *inactive*
> stripes.
> I know before stop, it uses O_EXCL open the md, but that won't stop others
> open it and send IO to it.
> So I think it's possible that some active stripes will be still running.
do_md_stop() calls sync_blockdev() which was supposed to wait for all
outstanding IO. It probably doesn't wait for reads though, only writes.
>
> And I also found
> commit 5aa61f427e4979be733e4847b9199ff9cc48a47e
> Author: NeilBrown <neilb@suse.de>
> Date: Mon Dec 15 12:56:57 2014 +1100
> md: split detach operation out from ->stop.
>
> add calling a quiesce before unregister raid5d in __md_stop, which not
> exists there before.
> Does this fix the hole when md stop?
Why don't you try it and see?
NeilBrown
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next prev parent reply other threads:[~2016-07-22 1:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-20 10:53 How does md gurantee not miss to free an active stripe_head when md stops? Vaughan
2016-07-22 1:15 ` NeilBrown [this message]
-- strict thread matches above, loose matches on Subject: below --
2016-07-18 9:18 Vaughan
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