[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag |
Date: |
Wed, 25 Apr 2018 09:33:24 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 |
On 04/21/2018 08:29 AM, Max Reitz wrote:
> This flag signifies that a write request will not change the visible
> disk content. With this flag set, it is sufficient to have the
> BLK_PERM_WRITE_UNCHANGED permission instead of BLK_PERM_WRITE.
>
> Signed-off-by: Max Reitz <address@hidden>
> Reviewed-by: Stefan Hajnoczi <address@hidden>
> Reviewed-by: Alberto Garcia <address@hidden>
> ---
> include/block/block.h | 6 +++++-
> block/io.c | 6 +++++-
> 2 files changed, 10 insertions(+), 2 deletions(-)
Since patch 5 adds an instance of a driver setting supported_write_flags
= BDRV_REQ_WRITE_UNCHANGED, I think this patch should tweak the
documentation of supported_write_flags (and supported_zero_flags?) in
block_int.h to mention that drivers can opt-in to supporting this
particular flag (rather than it being handled completely at the block
layer).
Also, that does raise the question of whether you have more work to
support write-zero requests with WRITE_UNCHANGED (which indeed sounds
like something plausible to support).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
signature.asc
Description: OpenPGP digital signature
- [Qemu-devel] [PATCH v2 0/9] block: Add COR filter driver, Max Reitz, 2018/04/21
- [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag, Max Reitz, 2018/04/21
- Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag,
Eric Blake <=
- Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag, Max Reitz, 2018/04/25
- Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag, Eric Blake, 2018/04/25
- Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag, Kevin Wolf, 2018/04/26
- Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag, Max Reitz, 2018/04/28
- Re: [Qemu-devel] [PATCH v2 3/9] block: Add BDRV_REQ_WRITE_UNCHANGED flag, Kevin Wolf, 2018/04/30
[Qemu-devel] [PATCH v2 4/9] block: Set BDRV_REQ_WRITE_UNCHANGED for COR writes, Max Reitz, 2018/04/21
[Qemu-devel] [PATCH v2 6/9] block: Support BDRV_REQ_WRITE_UNCHANGED in filters, Max Reitz, 2018/04/21
[Qemu-devel] [PATCH v2 5/9] block/quorum: Support BDRV_REQ_WRITE_UNCHANGED, Max Reitz, 2018/04/21
[Qemu-devel] [PATCH v2 7/9] iotests: Clean up wrap image in 197, Max Reitz, 2018/04/21
[Qemu-devel] [PATCH v2 8/9] iotests: Copy 197 for COR filter driver, Max Reitz, 2018/04/21