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Re: [Qemu-block] [Qemu-devel] [PATCH for-2.8 0/2] pass partial discard r
From: |
Laszlo Ersek |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH for-2.8 0/2] pass partial discard requests all the way down |
Date: |
Fri, 11 Nov 2016 11:09:06 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 11/11/16 00:10, Eric Blake wrote:
> Peter reported a mild regression in qemu 2.7 when targetting the
> Dell Equallogic iSCSI, which advertizes a preferred and maximum
> unmap alignment at 15M. In qemu 2.6, trims not aligned to those
> boundaries still made it to the device, but in 2.7, the block
> layer is ignoring unaligned portions of guest requests, resulting
> in fewer blocks being actually trimmed.
>
> Since discard is advisary,
advisory?
> it is borderline if this counts as a
> bug fix worthy for inclusion in 2.8, or if it should be deferred
> to 2.9. At any rate, while I was able to test that the patch
> didn't misbehave for me when I tweaked an NBD setup to force
> 15M alignment, I am unable to test that it makes an actual
> difference for Peter's hardware, and that needs to happen before
> anyone even thinks of applying this.
>
> Eric Blake (2):
> block: Return -ENOTSUP rather than assert on unaligned discards
> block: Pass unaligned discard requests to drivers
>
> block/io.c | 36 +++++++++++++++++++++++-------------
> block/iscsi.c | 4 +++-
> block/qcow2.c | 4 ++++
> block/sheepdog.c | 5 +++--
> 4 files changed, 33 insertions(+), 16 deletions(-)
>