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Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard |
Date: |
Wed, 6 May 2015 17:50:48 +0800 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Wed, 05/06 10:59, Paolo Bonzini wrote:
>
>
> On 06/05/2015 03:45, Fam Zheng wrote:
> >> > This is not enough, you also have to do the discard in block/mirror.c,
> >> > otherwise the destination image could even become fully provisioned!
> > I wasn't sure what if src and dest have different
> > can_write_zeroes_with_unmap
> > value, but your argument is stronger.
> >
> > I will add discard in mirror. Besides that, do we need to compare the
> > can_write_zeroes_with_unmap?
>
> Hmm, if can_write_zeroes_with_unmap is set, it's probably better to
> write zeroes instead of discarding, in case the guest is relying on it.
>
I think there are four cases:
# src can_write_zeroes_with_unmap target can_write_zeroes_with_unmap
--------------------------------------------------------------------------------
1 true true
2 true false
3 false true
4 false false
I think replicating discard only works for 1, because both side would then read
0. For case 2 & 3 it's probably better to mirror the actual reading of source.
I'm not sure about 4.
What do you think?
Fam
- [Qemu-devel] [PATCH 0/4] block: Mirror discarded sectors, Fam Zheng, 2015/05/05
- [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard, Fam Zheng, 2015/05/05
- Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard, Paolo Bonzini, 2015/05/05
- Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard, Fam Zheng, 2015/05/05
- Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard, Paolo Bonzini, 2015/05/06
- Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard,
Fam Zheng <=
- Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard, Paolo Bonzini, 2015/05/06
- Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard, Fam Zheng, 2015/05/11
- Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard, Paolo Bonzini, 2015/05/11
[Qemu-devel] [PATCH 2/4] block: Remove bdrv_reset_dirty, Fam Zheng, 2015/05/05
[Qemu-devel] [PATCH 3/4] qemu-iotests: Make block job methods common, Fam Zheng, 2015/05/05
[Qemu-devel] [PATCH 4/4] qemu-iotests: Add test case for mirror with unmap, Fam Zheng, 2015/05/05