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From c56d4b513e1a0b868b788ea495857f41cde1acf6 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 20:21:41 +0100
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Subject: [PATCH 15/49] block: Don't poll in parent drain callbacks
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20181010202213.7372-3-kwolf@redhat.com>
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Patchwork-id: 82592
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O-Subject: [RHEL-8 qemu-kvm PATCH 12/44] block: Don't poll in parent drain callbacks
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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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bdrv_do_drained_begin() is only safe if we have a single
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BDRV_POLL_WHILE() after quiescing all affected nodes. We cannot allow
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that parent callbacks introduce a nested polling loop that could cause
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graph changes while we're traversing the graph.
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Split off bdrv_do_drained_begin_quiesce(), which only quiesces a single
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node without waiting for its requests to complete. These requests will
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be waited for in the BDRV_POLL_WHILE() call down the call chain.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit dcf94a23b1add0f856db51e9ff5ba0774e096076)
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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.c | 2 +-
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block/io.c | 24 ++++++++++++++++--------
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include/block/block.h | 9 +++++++++
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3 files changed, 26 insertions(+), 9 deletions(-)
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diff --git a/block.c b/block.c
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index 9afaf26..5a50de6 100644
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--- a/block.c
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+++ b/block.c
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@@ -818,7 +818,7 @@ static char *bdrv_child_get_parent_desc(BdrvChild *c)
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static void bdrv_child_cb_drained_begin(BdrvChild *child)
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{
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BlockDriverState *bs = child->opaque;
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- bdrv_drained_begin(bs);
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+ bdrv_do_drained_begin_quiesce(bs, NULL);
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}
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static bool bdrv_child_cb_drained_poll(BdrvChild *child)
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diff --git a/block/io.c b/block/io.c
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index 442ded1..9c41ff9 100644
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--- a/block/io.c
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+++ b/block/io.c
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@@ -285,15 +285,10 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
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assert(data.done);
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}
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-void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,
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- BdrvChild *parent, bool poll)
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+void bdrv_do_drained_begin_quiesce(BlockDriverState *bs,
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+ BdrvChild *parent)
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{
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- BdrvChild *child, *next;
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-
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- if (qemu_in_coroutine()) {
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- bdrv_co_yield_to_drain(bs, true, recursive, parent, poll);
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- return;
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- }
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+ assert(!qemu_in_coroutine());
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/* Stop things in parent-to-child order */
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if (atomic_fetch_inc(&bs->quiesce_counter) == 0) {
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@@ -302,6 +297,19 @@ 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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+}
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+
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+static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,
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+ BdrvChild *parent, bool poll)
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+{
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+ BdrvChild *child, *next;
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+
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+ if (qemu_in_coroutine()) {
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+ bdrv_co_yield_to_drain(bs, true, recursive, parent, poll);
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+ return;
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+ }
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+
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+ bdrv_do_drained_begin_quiesce(bs, parent);
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if (recursive) {
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bs->recursive_quiesce_counter++;
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diff --git a/include/block/block.h b/include/block/block.h
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index 2bbea7c..43f29b5 100644
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--- a/include/block/block.h
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+++ b/include/block/block.h
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@@ -619,6 +619,15 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive,
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void bdrv_drained_begin(BlockDriverState *bs);
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/**
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+ * bdrv_do_drained_begin_quiesce:
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+ *
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+ * Quiesces a BDS like bdrv_drained_begin(), but does not wait for already
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+ * running requests to complete.
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+ */
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+void bdrv_do_drained_begin_quiesce(BlockDriverState *bs,
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+ BdrvChild *parent);
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+
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+/**
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* Like bdrv_drained_begin, but recursively begins a quiesced section for
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* exclusive access to all child nodes as well.
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*/
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--
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1.8.3.1
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