From: Avi Kivity <avi@redhat.com>
To: qemu-devel@nongnu.org
Cc: Uri Lublin <uril@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 00/14] block (mostly qcow2) changes (v6)
Date: Tue, 24 Mar 2009 13:44:49 +0200 [thread overview]
Message-ID: <49C8C7B1.1010406@redhat.com> (raw)
In-Reply-To: <20090324112257.GD30294@redhat.com>
Gleb Natapov wrote:
> On Tue, Mar 17, 2009 at 10:40:38PM +0200, Uri Lublin wrote:
>
>> Changes from v5:
>> Patchset includes newly introduced qcow2 extensions.
>> Usage of such qcow2 extensions for keeping both backing format and
>> highest-allocated-offset.
>> No scanning of qcow2 images upon open.
>>
> highest-allocated-offset is written to a disk only if block device was closed
> properly, so this value can't actually be trusted to be accurate. How
> important is to maintain it accurate? If it is important it should be
> saved on disk as part of a metadata update and if it is not it can be
> updated on a first guest write that requires new block allocation.
>
Good catch.
I suggest a different approach. Have a notification that triggers when
a write past a certain offset occurs:
(qemu) block_watermark_notify ide0-0 123564435343
... time passes ...
(qemu) #block watermark exceeded: ide0-0 127454566544
This is in addition to pausing the VM on write error.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
prev parent reply other threads:[~2009-03-24 11:45 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-17 20:40 [Qemu-devel] [PATCH 00/14] block (mostly qcow2) changes (v6) Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 01/14] Introducing qcow2 extensions Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 02/14] block: support known backing format for image create and open Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 03/14] block-qcow2: keep backing file format in a qcow2 extension Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 04/14] qemu-img: adding a "-F base_fmt" option to "qemu-img create -b" Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 05/14] block-qcow2: keep highest allocated offset Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 06/14] block-qcow2: export highest-alloc through BlockDriverInfo and get_info() Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 07/14] block: info blockstats: show highest_allocated if exists Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 08/14] Add a bdrv_close_all() and call it at the end of main() Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 09/14] block-qcow2: keep highest alloc offset in a qcow2 extension Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 10/14] qemu-img: info: show highest_alloc if exists Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 11/14] qcow2: qcow_read_extensions: make "advance offset over extension" common Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 12/14] block: pass BDRV_BACKING flag to open of a backing file Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 13/14] block: keep flags an image was opened with Uri Lublin
2009-03-17 20:40 ` [Qemu-devel] [PATCH 14/14] block-qcow2: do not keep track of highest-alloc for backing files Uri Lublin
2009-03-24 11:22 ` [Qemu-devel] [PATCH 00/14] block (mostly qcow2) changes (v6) Gleb Natapov
2009-03-24 11:44 ` Avi Kivity [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=49C8C7B1.1010406@redhat.com \
--to=avi@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=uril@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.