From c56d4b513e1a0b868b788ea495857f41cde1acf6 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 10 Oct 2018 20:21:41 +0100 Subject: [PATCH 15/49] block: Don't poll in parent drain callbacks RH-Author: Kevin Wolf Message-id: <20181010202213.7372-3-kwolf@redhat.com> Patchwork-id: 82592 O-Subject: [RHEL-8 qemu-kvm PATCH 12/44] block: Don't poll in parent drain callbacks Bugzilla: 1637976 RH-Acked-by: Max Reitz RH-Acked-by: John Snow RH-Acked-by: Thomas Huth bdrv_do_drained_begin() is only safe if we have a single BDRV_POLL_WHILE() after quiescing all affected nodes. We cannot allow that parent callbacks introduce a nested polling loop that could cause graph changes while we're traversing the graph. Split off bdrv_do_drained_begin_quiesce(), which only quiesces a single node without waiting for its requests to complete. These requests will be waited for in the BDRV_POLL_WHILE() call down the call chain. Signed-off-by: Kevin Wolf (cherry picked from commit dcf94a23b1add0f856db51e9ff5ba0774e096076) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- block.c | 2 +- block/io.c | 24 ++++++++++++++++-------- include/block/block.h | 9 +++++++++ 3 files changed, 26 insertions(+), 9 deletions(-) diff --git a/block.c b/block.c index 9afaf26..5a50de6 100644 --- a/block.c +++ b/block.c @@ -818,7 +818,7 @@ static char *bdrv_child_get_parent_desc(BdrvChild *c) static void bdrv_child_cb_drained_begin(BdrvChild *child) { BlockDriverState *bs = child->opaque; - bdrv_drained_begin(bs); + bdrv_do_drained_begin_quiesce(bs, NULL); } static bool bdrv_child_cb_drained_poll(BdrvChild *child) diff --git a/block/io.c b/block/io.c index 442ded1..9c41ff9 100644 --- a/block/io.c +++ b/block/io.c @@ -285,15 +285,10 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs, assert(data.done); } -void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, - BdrvChild *parent, bool poll) +void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, + BdrvChild *parent) { - BdrvChild *child, *next; - - if (qemu_in_coroutine()) { - bdrv_co_yield_to_drain(bs, true, recursive, parent, poll); - return; - } + assert(!qemu_in_coroutine()); /* Stop things in parent-to-child order */ if (atomic_fetch_inc(&bs->quiesce_counter) == 0) { @@ -302,6 +297,19 @@ void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, bdrv_parent_drained_begin(bs, parent); bdrv_drain_invoke(bs, true); +} + +static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, + BdrvChild *parent, bool poll) +{ + BdrvChild *child, *next; + + if (qemu_in_coroutine()) { + bdrv_co_yield_to_drain(bs, true, recursive, parent, poll); + return; + } + + bdrv_do_drained_begin_quiesce(bs, parent); if (recursive) { bs->recursive_quiesce_counter++; diff --git a/include/block/block.h b/include/block/block.h index 2bbea7c..43f29b5 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -619,6 +619,15 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive, void bdrv_drained_begin(BlockDriverState *bs); /** + * bdrv_do_drained_begin_quiesce: + * + * Quiesces a BDS like bdrv_drained_begin(), but does not wait for already + * running requests to complete. + */ +void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, + BdrvChild *parent); + +/** * Like bdrv_drained_begin, but recursively begins a quiesced section for * exclusive access to all child nodes as well. */ -- 1.8.3.1