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Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks |
Date: |
Fri, 18 Oct 2013 14:38:12 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Oct 08, 2013 at 01:58:08PM +0200, Peter Lieven wrote:
> this patch does 2 things:
> a) only do additional call outs if BDRV_BLOCK_ZERO is not already set.
> b) use the newly introduced bdrv_has_discard_zeroes() to return the
> zero state of an unallocated block. the used callout to
> bdrv_has_zero_init() is only valid right after bdrv_create.
>
> Reviewed-by: Eric Blake <address@hidden>
> Signed-off-by: Peter Lieven <address@hidden>
> ---
> block.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/block.c b/block.c
> index fc931e3..1be4418 100644
> --- a/block.c
> +++ b/block.c
> @@ -3247,8 +3247,8 @@ static int64_t coroutine_fn
> bdrv_co_get_block_status(BlockDriverState *bs,
> return ret;
> }
>
> - if (!(ret & BDRV_BLOCK_DATA)) {
> - if (bdrv_has_zero_init(bs)) {
> + if (!(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO)) {
> + if (bdrv_has_discard_zeroes(bs)) {
I'm a little unclear about the semantics of bdrv_has_discard_zeroes().
Originally I thought it just meant any blocks discarded will read back
as zeroes. But here it implies that any unallocated block reads
back as zeroes too?
In other words, this patch assumes unallocated blocks behave the same as
discarded blocks wrt to zeroes.
Stefan
- [Qemu-devel] [PATCHv4 01/17] block: make BdrvRequestFlags public, (continued)
- [Qemu-devel] [PATCHv4 01/17] block: make BdrvRequestFlags public, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 02/17] block: add flags to bdrv_*_write_zeroes, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 08/17] block: honour BlockLimits in bdrv_co_discard, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 06/17] block: add BlockLimits structure to BlockDriverState, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 07/17] block: honour BlockLimits in bdrv_co_do_write_zeroes, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 09/17] iscsi: simplify iscsi_co_discard, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 11/17] iscsi: add bdrv_has_discard_zeroes and bdrv_has_discard_write_zeroes, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 04/17] block: introduce bdrv_has_discard_zeroes and bdrv_has_discard_write_zeroes, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 10/17] iscsi: set limits in BlockDriverState, Peter Lieven, 2013/10/08
- [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Peter Lieven, 2013/10/08
- Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks,
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Peter Lieven, 2013/10/18
- Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Paolo Bonzini, 2013/10/18
- Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Peter Lieven, 2013/10/18
- Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Stefan Hajnoczi, 2013/10/30
- Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Peter Lieven, 2013/10/30
- Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Peter Lieven, 2013/10/18