From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51789) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fUxHO-0004qN-EP for qemu-devel@nongnu.org; Mon, 18 Jun 2018 12:45:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fUxHL-0006Ej-Hj for qemu-devel@nongnu.org; Mon, 18 Jun 2018 12:45:22 -0400 From: Kevin Wolf Date: Mon, 18 Jun 2018 18:44:37 +0200 Message-Id: <20180618164504.24488-9-kwolf@redhat.com> In-Reply-To: <20180618164504.24488-1-kwolf@redhat.com> References: <20180618164504.24488-1-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 08/35] block: Remove bdrv_drain_recurse() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org For bdrv_drain(), recursively waiting for child node requests is pointless because we didn't quiesce their parents, so new requests could come in anyway. Letting the function work only on a single node makes it more consistent. For subtree drains and drain_all, we already have the recursion in bdrv_do_drained_begin(), so the extra recursion doesn't add anything either. Remove the useless code. Signed-off-by: Kevin Wolf Reviewed-by: Stefan Hajnoczi --- block/io.c | 36 +++--------------------------------- 1 file changed, 3 insertions(+), 33 deletions(-) diff --git a/block/io.c b/block/io.c index 5820e73bb2..5f6d5eed52 100644 --- a/block/io.c +++ b/block/io.c @@ -219,38 +219,6 @@ static bool bdrv_drain_poll_top_level(BlockDriverState *bs, return bdrv_drain_poll(bs, ignore_parent); } -static bool bdrv_drain_recurse(BlockDriverState *bs, BdrvChild *parent) -{ - BdrvChild *child, *tmp; - bool waited; - - /* Wait for drained requests to finish */ - waited = BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent)); - - QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) { - BlockDriverState *bs = child->bs; - bool in_main_loop = - qemu_get_current_aio_context() == qemu_get_aio_context(); - assert(bs->refcnt > 0); - if (in_main_loop) { - /* In case the recursive bdrv_drain_recurse processes a - * block_job_defer_to_main_loop BH and modifies the graph, - * let's hold a reference to bs until we are done. - * - * IOThread doesn't have such a BH, and it is not safe to call - * bdrv_unref without BQL, so skip doing it there. - */ - bdrv_ref(bs); - } - waited |= bdrv_drain_recurse(bs, child); - if (in_main_loop) { - bdrv_unref(bs); - } - } - - return waited; -} - static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, BdrvChild *parent); static void bdrv_do_drained_end(BlockDriverState *bs, bool recursive, @@ -318,7 +286,9 @@ void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, bdrv_parent_drained_begin(bs, parent); bdrv_drain_invoke(bs, true); - bdrv_drain_recurse(bs, parent); + + /* Wait for drained requests to finish */ + BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent)); if (recursive) { bs->recursive_quiesce_counter++; -- 2.13.6