From: NeilBrown <neilb@suse.de>
To: Marcus Sorensen <shadowsor@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: quick question about write-intent bitmap
Date: Thu, 1 Dec 2011 18:18:52 +1100 [thread overview]
Message-ID: <20111201181852.5810ba4c@notabene.brown> (raw)
In-Reply-To: <CALFpzo6wwtmnyCGW+4OkZL=6=0OFPV3STREq56_5jJt9z_qX2g@mail.gmail.com>
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On Wed, 30 Nov 2011 23:34:13 -0700 Marcus Sorensen <shadowsor@gmail.com>
wrote:
> I would appreciate being pointed to any sort of in-depth documentation
> on how the write intent bitmap works. To make my question quick, I'm
> wondering how the write-intent bitmap holds up to writeback caching.
> It seems like md would assume that the cached writes had made it to
> disk, and only rebuild writes that happened since the disk was
> removed, leaving an inconsistent array.
>
md writes bitmaps with
REQ_WRITE | REQ_SYNC | REQ_FLUSH | REQ_FUA
If that returns before the data is truly safe, then you have a bug somewhere.
i.e. md tries to write-through an cache that might be in the way.
NeilBrown
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prev parent reply other threads:[~2011-12-01 7:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-01 6:34 quick question about write-intent bitmap Marcus Sorensen
2011-12-01 7:18 ` NeilBrown [this message]
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