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From e6d8bc54a031c61c1fce2c9e1ccdb821b5991c1a Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Wed, 10 Oct 2018 20:08:42 +0100
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Subject: [PATCH 11/49] block: Remove bdrv_drain_recurse()
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20181010200843.6710-9-kwolf@redhat.com>
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Patchwork-id: 82588
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O-Subject: [RHEL-8 qemu-kvm PATCH 08/44] block: Remove bdrv_drain_recurse()
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Bugzilla: 1637976
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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For bdrv_drain(), recursively waiting for child node requests is
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pointless because we didn't quiesce their parents, so new requests could
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come in anyway. Letting the function work only on a single node makes it
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more consistent.
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For subtree drains and drain_all, we already have the recursion in
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bdrv_do_drained_begin(), so the extra recursion doesn't add anything
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either.
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Remove the useless code.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit d30b8e64b7b282da785307504ada59efa8096fb1)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 block/io.c | 36 +++---------------------------------
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 1 file changed, 3 insertions(+), 33 deletions(-)
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diff --git a/block/io.c b/block/io.c
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index e260394..a0e3461 100644
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--- a/block/io.c
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+++ b/block/io.c
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@@ -218,38 +218,6 @@ static bool bdrv_drain_poll_top_level(BlockDriverState *bs,
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     return bdrv_drain_poll(bs, ignore_parent);
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 }
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-static bool bdrv_drain_recurse(BlockDriverState *bs, BdrvChild *parent)
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-{
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-    BdrvChild *child, *tmp;
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-    bool waited;
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-
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-    /* Wait for drained requests to finish */
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-    waited = BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));
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-
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-    QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {
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-        BlockDriverState *bs = child->bs;
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-        bool in_main_loop =
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-            qemu_get_current_aio_context() == qemu_get_aio_context();
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-        assert(bs->refcnt > 0);
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-        if (in_main_loop) {
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-            /* In case the recursive bdrv_drain_recurse processes a
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-             * block_job_defer_to_main_loop BH and modifies the graph,
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-             * let's hold a reference to bs until we are done.
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-             *
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-             * IOThread doesn't have such a BH, and it is not safe to call
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-             * bdrv_unref without BQL, so skip doing it there.
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-             */
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-            bdrv_ref(bs);
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-        }
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-        waited |= bdrv_drain_recurse(bs, child);
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-        if (in_main_loop) {
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-            bdrv_unref(bs);
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-        }
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-    }
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-
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-    return waited;
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-}
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-
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 static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,
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                                   BdrvChild *parent);
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 static void bdrv_do_drained_end(BlockDriverState *bs, bool recursive,
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@@ -317,7 +285,9 @@ void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,
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     bdrv_parent_drained_begin(bs, parent);
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     bdrv_drain_invoke(bs, true);
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-    bdrv_drain_recurse(bs, parent);
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+
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+    /* Wait for drained requests to finish */
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+    BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));
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     if (recursive) {
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         bs->recursive_quiesce_counter++;
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-- 
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1.8.3.1
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