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Re: [Qemu-block] [PATCH 6/9] block: Support BDRV_REQ_WRITE_UNCHANGED in
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [PATCH 6/9] block: Support BDRV_REQ_WRITE_UNCHANGED in filters |
Date: |
Fri, 20 Apr 2018 16:35:12 +0800 |
User-agent: |
Mutt/1.9.2 (2017-12-15) |
On Mon, Apr 16, 2018 at 06:58:46PM +0200, Max Reitz wrote:
> Update the rest of the filter drivers to support
> BDRV_REQ_WRITE_UNCHANGED. They already forward write request flags to
> their children, so we just have to announce support for it.
>
> This patch does not cover the replication driver because that currently
> does not support flags at all, and because it just grabs the WRITE
> permission for its children when it can, so we should be fine just
> submitting the incoming WRITE_UNCHANGED requests as normal writes.
>
> It also does not cover format drivers for similar reasons. They all use
> bdrv_format_default_perms() as their .bdrv_child_perm() implementation
> so they just always grab the WRITE permission for their file children
> whenever possible. In addition, it often would be difficult to
> ascertain whether incoming unchanging writes end up as unchanging writes
> in their files. So we just leave them as normal potentially changing
> writes.
>
> Signed-off-by: Max Reitz <address@hidden>
> ---
> block/blkdebug.c | 9 +++++----
> block/blkreplay.c | 3 +++
> block/blkverify.c | 3 +++
> block/cor.c | 10 ++++++----
> block/mirror.c | 2 ++
> block/raw-format.c | 9 +++++----
> block/throttle.c | 6 ++++--
> 7 files changed, 28 insertions(+), 14 deletions(-)
Reviewed-by: Stefan Hajnoczi <address@hidden>
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- [Qemu-block] [PATCH 5/9] block/quorum: Support BDRV_REQ_WRITE_UNCHANGED, (continued)
- [Qemu-block] [PATCH 5/9] block/quorum: Support BDRV_REQ_WRITE_UNCHANGED, Max Reitz, 2018/04/16
- [Qemu-block] [PATCH 4/9] block: Set BDRV_REQ_WRITE_UNCHANGED for COR writes, Max Reitz, 2018/04/16
- [Qemu-block] [PATCH 7/9] iotests: Clean up wrap image in 197, Max Reitz, 2018/04/16
- [Qemu-block] [PATCH 6/9] block: Support BDRV_REQ_WRITE_UNCHANGED in filters, Max Reitz, 2018/04/16
- [Qemu-block] [PATCH 8/9] iotests: Copy 197 for COR filter driver, Max Reitz, 2018/04/16
- [Qemu-block] [PATCH 9/9] iotests: Add test for COR across nodes, Max Reitz, 2018/04/16
- Re: [Qemu-block] [Qemu-devel] [PATCH 0/9] block: Add COR filter driver, Stefan Hajnoczi, 2018/04/20