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Re: [Qemu-devel] [PATCH] block: bdrv_invalidate_cache: invalidate childr

From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH] block: bdrv_invalidate_cache: invalidate children first
Date: Wed, 1 Feb 2017 03:03:38 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0

On 31.01.2017 12:23, Vladimir Sementsov-Ogievskiy wrote:
> Current implementation invalidates firstly parent bds and then its
> children. This leads to the following bug:
> after incoming migration, in bdrv_invalidate_cache_all:
> 1. invalidate parent bds - reopen it with BDRV_O_INACTIVE cleared
> 2. child is not yet invalidated
> 3. parent check that its BDRV_O_INACTIVE is cleared
> 4. parent writes to child
> 5. assert in bdrv_co_pwritev, as BDRV_O_INACTIVE is set for child
> This patch fixes it by just changing invalidate sequence: invalidate
> children first.
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> v2: I've missed that bdrv_invalidate_cache is already recursive, so we
> can change sequence here. Also v1 doesn't cover the case when
> bdrv_invalidate_cache is called not from bdrv_invalidate_cache_all.
>  block.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)

Reviewed-by: Max Reitz <address@hidden>

I'll wait a bit until I apply this patch (please remind me next week if
I forget it...), though, because migration-related things are not
exactly my forte, so maybe someone else has something to say.


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