From e6d8bc54a031c61c1fce2c9e1ccdb821b5991c1a Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 10 Oct 2018 20:08:42 +0100 Subject: [PATCH 11/49] block: Remove bdrv_drain_recurse() RH-Author: Kevin Wolf Message-id: <20181010200843.6710-9-kwolf@redhat.com> Patchwork-id: 82588 O-Subject: [RHEL-8 qemu-kvm PATCH 08/44] block: Remove bdrv_drain_recurse() Bugzilla: 1637976 RH-Acked-by: Max Reitz RH-Acked-by: John Snow RH-Acked-by: Thomas Huth 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 (cherry picked from commit d30b8e64b7b282da785307504ada59efa8096fb1) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- block/io.c | 36 +++--------------------------------- 1 file changed, 3 insertions(+), 33 deletions(-) diff --git a/block/io.c b/block/io.c index e260394..a0e3461 100644 --- a/block/io.c +++ b/block/io.c @@ -218,38 +218,6 @@ 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, @@ -317,7 +285,9 @@ 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++; -- 1.8.3.1