From 67da1dc5ce696c7b309b1db100da7d94292847b7 Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Mon, 9 Nov 2015 18:16:53 +0800 Subject: block: Introduce BlockDriver.bdrv_drain callback Drivers can have internal request sources that generate IO, like the need_check_timer in QED. Since we want quiesced periods that contain nested event loops in block layer, we need to have a way to disable such event sources. Block drivers must implement the "bdrv_drain" callback if it has any internal sources that can generate I/O activity, like a timer or a worker thread (even in a library) that can schedule QEMUBH in an asynchronous callback. Update the comments of bdrv_drain and bdrv_drained_begin accordingly. Like bdrv_requests_pending(), we should consider all the children of bs. Before, the while loop just works, as bdrv_requests_pending() already tracks its children; now we mustn't miss the callback, so recurse down explicitly. Signed-off-by: Fam Zheng Reviewed-by: Paolo Bonzini Message-id: 1447064214-29930-9-git-send-email-famz@redhat.com Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- include/block/block_int.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/block') diff --git a/include/block/block_int.h b/include/block/block_int.h index 84991d9973..3a24913a7e 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -295,6 +295,12 @@ struct BlockDriver { */ int (*bdrv_probe_geometry)(BlockDriverState *bs, HDGeometry *geo); + /** + * Drain and stop any internal sources of requests in the driver, and + * remain so until next I/O callback (e.g. bdrv_co_writev) is called. + */ + void (*bdrv_drain)(BlockDriverState *bs); + QLIST_ENTRY(BlockDriver) list; }; -- cgit v1.2.3