From: Eric Blake <eblake@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org,
Max Reitz <mreitz@redhat.com>
Subject: Re: [PATCH 1/4] block: Add bdrv_make_empty()
Date: Tue, 28 Apr 2020 09:07:27 -0500 [thread overview]
Message-ID: <f9b2b26a-eacd-93db-f5c1-2682ae597e24@redhat.com> (raw)
In-Reply-To: <20200428140132.GF5789@linux.fritz.box>
On 4/28/20 9:01 AM, Kevin Wolf wrote:
>> Can we please fix this to take a flags parameter? I want to make it easier
>> for callers to request BDRV_REQ_NO_FALLBACK for distinguishing between
>> callers where the image must be made empty (read as all zeroes) regardless
>> of time spent, vs. made empty quickly (including if it is already all zero)
>> but where the caller is prepared for the operation to fail and will write
>> zeroes itself if fast bulk zeroing was not possible.
>
> bdrv_make_empty() is not for making an image read as all zeroes, but to
> make it fully unallocated so that the backing file becomes visible.
>
> Are you confusing it with bdrv_make_zero(), which is just a wrapper
> around bdrv_pwrite_zeroes() and does take flags?
Yes. Although now I'm wondering if the two should remain separate or
should just be a single driver callback where flags can include
BDRV_REQ_ZERO_WRITE to distinguish whether exposing the backing file vs.
reading as all zeroes is intended, or if that is merging too much.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2020-04-28 14:10 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 13:26 [PATCH 0/4] block: Do not call BlockDriver.bdrv_make_empty() directly Max Reitz
2020-04-28 13:26 ` [PATCH 1/4] block: Add bdrv_make_empty() Max Reitz
2020-04-28 13:53 ` Eric Blake
2020-04-28 14:01 ` Kevin Wolf
2020-04-28 14:07 ` Eric Blake [this message]
2020-04-28 14:16 ` Kevin Wolf
2020-04-28 14:25 ` Eric Blake
2020-04-28 14:21 ` Kevin Wolf
2020-04-29 7:39 ` Max Reitz
2020-04-28 13:26 ` [PATCH 2/4] block: Use bdrv_make_empty() where possible Max Reitz
2020-04-28 13:54 ` Eric Blake
2020-04-28 15:03 ` Kevin Wolf
2020-04-28 13:26 ` [PATCH 3/4] block: Add blk_make_empty() Max Reitz
2020-04-28 13:55 ` Eric Blake
2020-04-28 14:28 ` Eric Blake
2020-04-28 14:47 ` Kevin Wolf
2020-04-29 7:39 ` Max Reitz
2020-04-28 13:26 ` [PATCH 4/4] block: Use blk_make_empty() after commits Max Reitz
2020-04-28 14:07 ` Eric Blake
2020-04-29 7:58 ` Max Reitz
2020-04-28 15:03 ` Kevin Wolf
2020-04-29 8:01 ` Max Reitz
2020-04-28 13:38 ` [PATCH 0/4] block: Do not call BlockDriver.bdrv_make_empty() directly no-reply
2020-04-28 13:43 ` no-reply
2020-04-28 13:57 ` Eric Blake
2020-04-28 13:48 ` no-reply
2020-04-28 13:49 ` Eric Blake
2020-04-28 14:05 ` Eric Blake
2020-04-28 14:53 ` no-reply
2020-04-28 14:57 ` no-reply
2020-04-28 15:02 ` no-reply
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