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[Qemu-block] [PATCH v2 12/20] block: Don't poll in parent drain callback
From: |
Kevin Wolf |
Subject: |
[Qemu-block] [PATCH v2 12/20] block: Don't poll in parent drain callbacks |
Date: |
Tue, 29 May 2018 19:21:48 +0200 |
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 <address@hidden>
---
include/block/block.h | 9 +++++++++
block.c | 2 +-
block/io.c | 24 ++++++++++++++++--------
3 files changed, 26 insertions(+), 9 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index 56962e7ee7..6026c1385e 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -589,6 +589,15 @@ 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.
*/
diff --git a/block.c b/block.c
index 8ca2cf27b4..1405d1180b 100644
--- a/block.c
+++ b/block.c
@@ -817,7 +817,7 @@ 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 01784d1115..af14227af8 100644
--- a/block/io.c
+++ b/block/io.c
@@ -286,15 +286,10 @@ 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) {
@@ -303,6 +298,19 @@ 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++;
--
2.13.6
- [Qemu-block] [PATCH v2 01/20] test-bdrv-drain: bdrv_drain() works with cross-AioContext events, (continued)
- [Qemu-block] [PATCH v2 01/20] test-bdrv-drain: bdrv_drain() works with cross-AioContext events, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 02/20] block: Use bdrv_do_drain_begin/end in bdrv_drain_all(), Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 03/20] block: Remove 'recursive' parameter from bdrv_drain_invoke(), Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 04/20] block: Don't manually poll in bdrv_drain_all(), Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 05/20] tests/test-bdrv-drain: bdrv_drain_all() works in coroutines now, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 06/20] block: Avoid unnecessary aio_poll() in AIO_WAIT_WHILE(), Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 07/20] block: Really pause block jobs on drain, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 08/20] block: Remove bdrv_drain_recurse(), Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 09/20] test-bdrv-drain: Add test for node deletion, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 11/20] test-bdrv-drain: Test node deletion in subtree recursion, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 12/20] block: Don't poll in parent drain callbacks,
Kevin Wolf <=
- [Qemu-block] [PATCH v2 10/20] block: Drain recursively with a single BDRV_POLL_WHILE(), Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 13/20] test-bdrv-drain: Graph change through parent callback, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 14/20] block: Defer .bdrv_drain_begin callback to polling phase, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 16/20] block: Allow AIO_WAIT_WHILE with NULL ctx, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 15/20] test-bdrv-drain: Test that bdrv_drain_invoke() doesn't poll, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 17/20] block: Move bdrv_drain_all_begin() out of coroutine context, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 19/20] block: Allow graph changes in bdrv_drain_all_begin/end sections, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 18/20] block: ignore_bds_parents parameter for drain functions, Kevin Wolf, 2018/05/29
- [Qemu-block] [PATCH v2 20/20] test-bdrv-drain: Test graph changes in drain_all section, Kevin Wolf, 2018/05/29
- Re: [Qemu-block] [Qemu-devel] [PATCH v2 00/20] Drain fixes and cleanups, part 3, no-reply, 2018/05/29