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Re: [Qemu-devel] [PATCH 1/4 for-2.11?] block/dirty-bitmap: add lock to b
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 1/4 for-2.11?] block/dirty-bitmap: add lock to bdrv_enable/disable_dirty_bitmap |
Date: |
Mon, 13 Nov 2017 11:50:50 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 |
On 11/13/2017 10:20 AM, Vladimir Sementsov-Ogievskiy wrote:
> Like other setters here these functions should take a lock.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> block/dirty-bitmap.c | 4 ++++
> 1 file changed, 4 insertions(+)
Should this patch be in 2.11?
>
> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index bd04e991b1..2a0bcd9e51 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
> @@ -397,15 +397,19 @@ void
> bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
> /* Called with BQL taken. */
> void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
> {
> + bdrv_dirty_bitmap_lock(bitmap);
> assert(!bdrv_dirty_bitmap_frozen(bitmap));
> bitmap->disabled = true;
> + bdrv_dirty_bitmap_unlock(bitmap);
Why do we need this lock in addition to BQL?
> }
>
> /* Called with BQL taken. */
> void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
> {
> + bdrv_dirty_bitmap_lock(bitmap);
> assert(!bdrv_dirty_bitmap_frozen(bitmap));
> bitmap->disabled = false;
> + bdrv_dirty_bitmap_unlock(bitmap);
Again, why do we need this in addition to BQL?
The commit message needs more details about a scenario where our
existing BQL lock is insufficient to prevent misuse of bitmap->disabled.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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- [Qemu-devel] [PATCH for-2.12 0/4] qmp dirty bitmap API, Vladimir Sementsov-Ogievskiy, 2017/11/13
- [Qemu-devel] [PATCH 1/4] block/dirty-bitmap: add lock to bdrv_enable/disable_dirty_bitmap, Vladimir Sementsov-Ogievskiy, 2017/11/13
- Re: [Qemu-devel] [PATCH 1/4 for-2.11?] block/dirty-bitmap: add lock to bdrv_enable/disable_dirty_bitmap,
Eric Blake <=
- [Qemu-devel] [PATCH 3/4] qmp: transaction support for block-dirty-bitmap-enable/disable, Vladimir Sementsov-Ogievskiy, 2017/11/13
- [Qemu-devel] [PATCH 4/4] qapi: add block-dirty-bitmap-merge, Vladimir Sementsov-Ogievskiy, 2017/11/13
- [Qemu-devel] [PATCH 2/4] qapi: add block-dirty-bitmap-enable/disable, Vladimir Sementsov-Ogievskiy, 2017/11/13
- Re: [Qemu-devel] [PATCH for-2.12 0/4] qmp dirty bitmap API, John Snow, 2017/11/15