Hi!
20.02.2019 21:01, John Snow wrote:
> When bitmaps are persistent, they may incur a disk read or write when bitmaps
> are added or removed. For configurations like virtio-dataplane, failing to
> acquire this lock will abort QEMU when disk IO occurs.
>
> We used to acquire aio_context as part of the bitmap lookup, so re-introduce
> the lock for just the cases that have an IO penalty. Commit 2119882c removed
> these locks, and I failed to notice this when we committed fd5ae4cc, so this
> has been broken since persistent bitmaps were introduced.
>
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1672010
> Reported-By: Aihua Liang <ali...@redhat.com>
> Signed-off-by: John Snow <js...@redhat.com>
> Reviewed-by: Eric Blake <ebl...@redhat.com>
> Message-id: 20190218233154.19303-1-js...@redhat.com
> Signed-off-by: John Snow <js...@redhat.com>
> ---
[..]
> void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
> @@ -2878,6 +2885,7 @@ void qmp_block_dirty_bitmap_remove(const char *node,
> const char *name,
> BlockDriverState *bs;
> BdrvDirtyBitmap *bitmap;
> Error *local_err = NULL;
> + AioContext *aio_context = NULL;
>
> bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
> if (!bitmap || !bs) {
> @@ -2892,14 +2900,20 @@ void qmp_block_dirty_bitmap_remove(const char *node,
> const char *name,
> }
>
> if (bdrv_dirty_bitmap_get_persistance(bitmap)) {
> + aio_context = bdrv_get_aio_context(bs);
> + aio_context_acquire(aio_context);
> bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
> if (local_err != NULL) {
> error_propagate(errp, local_err);
> - return;
> + goto out;
> }
> }
>
> bdrv_release_dirty_bitmap(bs, bitmap);
> + out:
> + if (aio_context) {
> + aio_context_release(aio_context);
> + }
> }
>
> /**
>
A bit late, but I have a question:
Why did you include bdrv_release_dirty_bitmap call into context-acquired
section? As I can
understand from commit message, it's not actually needed?
--
Best regards,
Vladimir
