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 --- block/io.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) (limited to 'block') diff --git a/block/io.c b/block/io.c index 4ecb171..adc1eab 100644 --- a/block/io.c +++ b/block/io.c @@ -237,8 +237,21 @@ bool bdrv_requests_pending(BlockDriverState *bs) return false; } +static void bdrv_drain_recurse(BlockDriverState *bs) +{ + BdrvChild *child; + + if (bs->drv && bs->drv->bdrv_drain) { + bs->drv->bdrv_drain(bs); + } + QLIST_FOREACH(child, &bs->children, next) { + bdrv_drain_recurse(child->bs); + } +} + /* - * Wait for pending requests to complete on a single BlockDriverState subtree + * Wait for pending requests to complete on a single BlockDriverState subtree, + * and suspend block driver's internal I/O until next request arrives. * * Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState * AioContext. @@ -251,6 +264,7 @@ void bdrv_drain(BlockDriverState *bs) { bool busy = true; + bdrv_drain_recurse(bs); while (busy) { /* Keep iterating */ bdrv_flush_io_queue(bs); -- cgit v1.1