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[Qemu-devel] [PATCH 05/20] block: change drain to look only at one child
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 05/20] block: change drain to look only at one child at a time |
Date: |
Mon, 17 Oct 2016 15:54:15 +0200 |
bdrv_requests_pending is checking children to also wait until internal
requests (such as metadata writes) have completed. However, checking
children is in general overkill. Children requests can be of two kinds:
- requests caused by an operation on bs, e.g. a bdrv_aio_write to bs
causing a write to bs->file->bs. In this case, the parent's in_flight
count will always be incremented by at least one for every request in
the child.
- asynchronous metadata writes or flushes. Such writes can be started
even if bs's in_flight count is zero, but not after the .bdrv_drain
callback has been invoked.
This patch therefore changes bdrv_drain to finish I/O in the parent
(after which the parent's in_flight will be locked to zero), call
bdrv_drain (after which the parent will not generate I/O on the child
anymore), and then wait for internal I/O in the children to complete.
Signed-off-by: Paolo Bonzini <address@hidden>
---
block/io.c | 47 ++++++++++++++++++++++++++---------------------
1 file changed, 26 insertions(+), 21 deletions(-)
diff --git a/block/io.c b/block/io.c
index 8d46d8b..afec968 100644
--- a/block/io.c
+++ b/block/io.c
@@ -156,16 +156,33 @@ bool bdrv_requests_pending(BlockDriverState *bs)
return false;
}
-static void bdrv_drain_recurse(BlockDriverState *bs)
+static bool bdrv_drain_poll(BlockDriverState *bs)
+{
+ bool waited = false;
+
+ while (atomic_read(&bs->in_flight) > 0) {
+ aio_poll(bdrv_get_aio_context(bs), true);
+ waited = true;
+ }
+ return waited;
+}
+
+static bool bdrv_drain_recurse(BlockDriverState *bs)
{
BdrvChild *child;
+ bool waited;
+
+ waited = bdrv_drain_poll(bs);
if (bs->drv && bs->drv->bdrv_drain) {
bs->drv->bdrv_drain(bs);
}
+
QLIST_FOREACH(child, &bs->children, next) {
- bdrv_drain_recurse(child->bs);
+ waited |= bdrv_drain_recurse(child->bs);
}
+
+ return waited;
}
typedef struct {
@@ -174,14 +191,6 @@ typedef struct {
bool done;
} BdrvCoDrainData;
-static void bdrv_drain_poll(BlockDriverState *bs)
-{
- while (bdrv_requests_pending(bs)) {
- /* Keep iterating */
- aio_poll(bdrv_get_aio_context(bs), true);
- }
-}
-
static void bdrv_co_drain_bh_cb(void *opaque)
{
BdrvCoDrainData *data = opaque;
@@ -189,7 +198,7 @@ static void bdrv_co_drain_bh_cb(void *opaque)
BlockDriverState *bs = data->bs;
bdrv_dec_in_flight(bs);
- bdrv_drain_poll(bs);
+ bdrv_drained_begin(bs);
data->done = true;
qemu_coroutine_enter(co);
}
@@ -220,6 +229,11 @@ static void coroutine_fn
bdrv_co_yield_to_drain(BlockDriverState *bs)
void bdrv_drained_begin(BlockDriverState *bs)
{
+ if (qemu_in_coroutine()) {
+ bdrv_co_yield_to_drain(bs);
+ return;
+ }
+
if (!bs->quiesce_counter++) {
aio_disable_external(bdrv_get_aio_context(bs));
bdrv_parent_drained_begin(bs);
@@ -227,11 +241,6 @@ void bdrv_drained_begin(BlockDriverState *bs)
bdrv_io_unplugged_begin(bs);
bdrv_drain_recurse(bs);
- if (qemu_in_coroutine()) {
- bdrv_co_yield_to_drain(bs);
- } else {
- bdrv_drain_poll(bs);
- }
bdrv_io_unplugged_end(bs);
}
@@ -299,7 +308,6 @@ void bdrv_drain_all(void)
aio_context_acquire(aio_context);
bdrv_parent_drained_begin(bs);
bdrv_io_unplugged_begin(bs);
- bdrv_drain_recurse(bs);
aio_context_release(aio_context);
if (!g_slist_find(aio_ctxs, aio_context)) {
@@ -322,10 +330,7 @@ void bdrv_drain_all(void)
aio_context_acquire(aio_context);
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
if (aio_context == bdrv_get_aio_context(bs)) {
- if (bdrv_requests_pending(bs)) {
- aio_poll(aio_context, true);
- waited = true;
- }
+ waited |= bdrv_drain_recurse(bs);
}
}
aio_context_release(aio_context);
--
2.7.4
- [Qemu-devel] [PATCH v2 00/20] dataplane: remove RFifoLock, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 01/20] replication: interrupt failover if the main device is closed, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 02/20] blockjob: introduce .drain callback for jobs, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 03/20] mirror: use bdrv_drained_begin/bdrv_drained_end, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 04/20] block: add BDS field to count in-flight requests, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 05/20] block: change drain to look only at one child at a time,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 06/20] qed: Implement .bdrv_drain, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 07/20] block: introduce BDRV_POLL_WHILE, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 09/20] nfs: use BDRV_POLL_WHILE, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 08/20] nfs: move nfs_set_events out of the while loops, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 11/20] aio: introduce qemu_get_current_aio_context, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 10/20] sheepdog: use BDRV_POLL_WHILE, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 12/20] iothread: detach all block devices before stopping them, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 13/20] replication: pass BlockDriverState to reopen_backing_file, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 14/20] block: prepare bdrv_reopen_multiple to release AioContext, Paolo Bonzini, 2016/10/17
- [Qemu-devel] [PATCH 15/20] qemu-io: acquire AioContext, Paolo Bonzini, 2016/10/17