From: Christoph Hellwig <hch@infradead.org>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Amir Goldstein <amir73il@gmail.com>,
Brian Foster <bfoster@redhat.com>,
fstests <fstests@vger.kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>
Subject: Re: [PATCH 1/4] generic: require discard zero behavior for dmlogwrites on XFS
Date: Thu, 27 Aug 2020 18:02:42 +0100 [thread overview]
Message-ID: <20200827170242.GA16905@infradead.org> (raw)
In-Reply-To: <c59a4ed6-2698-ab61-6a73-143e273d9e22@toxicpanda.com>
On Thu, Aug 27, 2020 at 11:57:03AM -0400, Josef Bacik wrote:
> This sort of brings up a good point, the whole point of DISCARD support in
> log-writes was to expose problems where we may have been discarding real
> data we cared about, hence adding the forced zero'ing stuff for devices that
> didn't support discard. But that made the incorrect assumption that a drive
> with actual discard support would actually return 0's for discarded data.
> That assumption was based on hardware that did actually do that, but now we
> live in the brave new world of significantly shittier drives. Does dm-thinp
> reliably unmap the ranges we discard, and thus give us this zero'ing
> behavior? Because we might as well just use that for everything so
> log-writes doesn't have to resort to pwrite()'ing zeros everywhere. Thanks,
We have a write zeroes operation in the block layer. For some devices
this is as efficient as discard, and that should (I think) dm.
next prev parent reply other threads:[~2020-08-27 17:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-26 14:38 [PATCH 0/4] fix up generic dmlogwrites tests to work with XFS Brian Foster
2020-08-26 14:38 ` [PATCH 1/4] generic: require discard zero behavior for dmlogwrites on XFS Brian Foster
2020-08-27 6:58 ` Amir Goldstein
2020-08-27 7:02 ` Christoph Hellwig
2020-08-27 7:29 ` Amir Goldstein
2020-08-27 7:37 ` Christoph Hellwig
2020-08-27 15:57 ` Josef Bacik
2020-08-27 17:02 ` Christoph Hellwig [this message]
2020-08-27 18:35 ` Brian Foster
2020-08-29 6:46 ` Christoph Hellwig
2020-08-30 13:30 ` Amir Goldstein
2020-08-31 13:37 ` Brian Foster
2020-08-29 6:44 ` Christoph Hellwig
2020-08-27 14:11 ` Brian Foster
[not found] ` <CAOQ4uxj6RKX01kKKc_SGZJegWEKaF+D8ZNJGALvh4o0c5bBcBg@mail.gmail.com>
2020-08-28 14:10 ` Brian Foster
2020-08-27 7:38 ` Christoph Hellwig
2020-08-26 14:38 ` [PATCH 2/4] generic/455: use thin volume for dmlogwrites target device Brian Foster
2020-08-26 14:38 ` [PATCH 3/4] generic/457: " Brian Foster
2020-08-26 14:38 ` [PATCH 4/4] generic/470: " Brian Foster
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