From 6d4f47108b6e121924f7bf12c97cbabb674dee1b Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

Date: Fri, 14 Sep 2018 10:55:06 +0200

Subject: [PATCH 15/49] block: Remove bdrv_drain_recurse()

RH-Author: Kevin Wolf <kwolf@redhat.com>

Message-id: <20180914105540.18077-9-kwolf@redhat.com>

Patchwork-id: 82161

O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 08/42] block: Remove bdrv_drain_recurse()

Bugzilla: 1601212

RH-Acked-by: John Snow <jsnow@redhat.com>

RH-Acked-by: Max Reitz <mreitz@redhat.com>

RH-Acked-by: Fam Zheng <famz@redhat.com>

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 <kwolf@redhat.com>

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

(cherry picked from commit d30b8e64b7b282da785307504ada59efa8096fb1)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 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