From: Eric Blake <eblake@redhat.com>
To: Bug 1884831 <1884831@bugs.launchpad.net>, qemu-devel@nongnu.org
Subject: Re: [Bug 1884831] Re: qemu-nbd fails to discard bigger chunks
Date: Wed, 22 Jul 2020 16:41:26 -0500 [thread overview]
Message-ID: <2be4be2c-bf5b-439c-a436-b6cb61fb13eb@redhat.com> (raw)
In-Reply-To: <159294814773.16548.4367549975584519679.malone@chaenomeles.canonical.com>
On 6/23/20 4:35 PM, Eric Blake wrote:
> Let's get nbd.ko out of the picture. The problem can be reproduced in
> user space (here, where I built qemu-nbd to log trace messages to
> stderr):
>
> $ truncate --size=3G file
> $ qemu-nbd -f raw file --trace=nbd_\*
> $ nbdsh -u nbd://localhost:10810 -c 'h.trim(3*1024*1024*1024,0)'
> nbd.Error: nbd_trim: trim: command failed: Input/output error (EIO)
>
>
> so this is definitely a case of qemu as NBD server NOT honoring requests
> between 2G and 4G. I'll have a patch posted soon.
https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg06592.html
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
WARNING: multiple messages have this Message-ID (diff)
From: Eric Blake <1884831@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: Re: [Bug 1884831] Re: qemu-nbd fails to discard bigger chunks
Date: Wed, 22 Jul 2020 21:41:26 -0000 [thread overview]
Message-ID: <2be4be2c-bf5b-439c-a436-b6cb61fb13eb@redhat.com> (raw)
Message-ID: <20200722214126.8tiuf3TZpSJltqVLjD8FrBpdio0Kb4hg133P1957h-c@z> (raw)
In-Reply-To: 159294814773.16548.4367549975584519679.malone@chaenomeles.canonical.com
On 6/23/20 4:35 PM, Eric Blake wrote:
> Let's get nbd.ko out of the picture. The problem can be reproduced in
> user space (here, where I built qemu-nbd to log trace messages to
> stderr):
>
> $ truncate --size=3G file
> $ qemu-nbd -f raw file --trace=nbd_\*
> $ nbdsh -u nbd://localhost:10810 -c 'h.trim(3*1024*1024*1024,0)'
> nbd.Error: nbd_trim: trim: command failed: Input/output error (EIO)
>
>
> so this is definitely a case of qemu as NBD server NOT honoring requests
> between 2G and 4G. I'll have a patch posted soon.
https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg06592.html
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1884831
Title:
qemu-nbd fails to discard bigger chunks
Status in QEMU:
New
Bug description:
This report is moved from systemd to here:
https://github.com/systemd/systemd/issues/16242
A qemu-nbd device reports that it can discard a lot of bytes:
cat /sys/block/nbd0/queue/discard_max_bytes
2199023255040
And indeed, discard works with small images:
$ qemu-img create -f qcow2 /tmp/image.img 2M
$ sudo qemu-nbd --connect=/dev/nbd0 /tmp/image.img
$ sudo blkdiscard /dev/nbd0
but not for bigger ones (still smaller than discard_max_bytes):
$ qemu-img create -f qcow2 /tmp/image.img 5G
$ sudo qemu-nbd --connect=/dev/nbd0 /tmp/image.img
$ sudo blkdiscard /dev/nbd0
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1884831/+subscriptions
next prev parent reply other threads:[~2020-07-22 21:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 20:19 [Bug 1884831] [NEW] qemu-nbd fails to discard bigger chunks TobiasHunger
2020-06-23 20:38 ` Eric Blake
2020-06-23 20:38 ` [Bug 1884831] " Eric Blake
2020-06-23 20:53 ` Eric Blake
2020-06-23 21:16 ` Eric Blake
2020-06-23 21:16 ` [Bug 1884831] [NEW] " Launchpad Bug Tracker
2020-06-23 21:35 ` [Bug 1884831] " Eric Blake
2020-07-22 21:41 ` Eric Blake [this message]
2020-07-22 21:41 ` Eric Blake
2021-05-07 2:53 ` Thomas Huth
2021-05-07 12:30 ` Eric Blake
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