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Re: [Qemu-stable] [Qemu-devel] [PATCH for-2.8 0/2] pass partial discard


From: Laszlo Ersek
Subject: Re: [Qemu-stable] [Qemu-devel] [PATCH for-2.8 0/2] pass partial discard requests all the way down
Date: Fri, 11 Nov 2016 11:11:55 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 11/11/16 11:09, Laszlo Ersek wrote:
> 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?

Ehh, sorry, I missed that this msg wouldn't be committed; it's just the
blurb for the series. The actual commits and the code have the right
spelling. Not gratuitously trying to be a smart-ass...

Laszlo

>> 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(-)
>>
> 




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