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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 09:45:33 +0800 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Tue, 05/05 15:06, Paolo Bonzini wrote:
>
>
> On 05/05/2015 14:46, Fam Zheng wrote:
> > Unsetting dirty globally with discard is not very correct. The discard may
> > zero
> > out sectors (depending on can_write_zeroes_with_unmap), we should replicate
> > this change to destinition side to make sure that the guest sees the same
> > data.
> >
> > Calling bdrv_reset_dirty also troubles mirror job because the hbitmap
> > iterator
> > doesn't expect unsetting of bits after current position.
> >
> > So let's do it the opposite way which fixes both problems: set the dirty
> > bits
> > if we are to discard it.
>
> 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?
Fam
>
> Paolo
>
> > Reported-by: address@hidden
> > Signed-off-by: Fam Zheng <address@hidden>
> > ---
> > block/io.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/block/io.c b/block/io.c
> > index 1ce62c4..809688b 100644
> > --- a/block/io.c
> > +++ b/block/io.c
> > @@ -2343,8 +2343,6 @@ int coroutine_fn bdrv_co_discard(BlockDriverState
> > *bs, int64_t sector_num,
> > return -EROFS;
> > }
> >
> > - bdrv_reset_dirty(bs, sector_num, nb_sectors);
> > -
> > /* Do nothing if disabled. */
> > if (!(bs->open_flags & BDRV_O_UNMAP)) {
> > return 0;
> > @@ -2354,6 +2352,8 @@ int coroutine_fn bdrv_co_discard(BlockDriverState
> > *bs, int64_t sector_num,
> > return 0;
> > }
> >
> > + bdrv_set_dirty(bs, sector_num, nb_sectors);
> > +
> > max_discard = MIN_NON_ZERO(bs->bl.max_discard,
> > BDRV_REQUEST_MAX_SECTORS);
> > while (nb_sectors > 0) {
> > int ret;
> >
- [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 <=
- 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, 2015/05/06
- 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