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[Qemu-devel] [PATCH v5 02/18] block: stop relying on io_flush() in bdrv_
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH v5 02/18] block: stop relying on io_flush() in bdrv_drain_all() |
Date: |
Mon, 1 Jul 2013 14:18:33 +0200 |
If a block driver has no file descriptors to monitor but there are still
active requests, it can return 1 from .io_flush(). This is used to spin
during synchronous I/O.
Stop relying on .io_flush() and instead check
QLIST_EMPTY(&bs->tracked_requests) to decide whether there are active
requests.
This is the first step in removing .io_flush() so that event loops no
longer need to have the concept of synchronous I/O. Eventually we may
be able to kill synchronous I/O completely by running everything in a
coroutine, but that is future work.
Note this patch moves bs->throttled_reqs initialization to bdrv_new() so
that bdrv_requests_pending(bs) can safely access it. In practice bs is
g_malloc0() so the memory is already zeroed but it's safer to initialize
the queue properly.
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block.c | 46 +++++++++++++++++++++++++++++++++++-----------
1 file changed, 35 insertions(+), 11 deletions(-)
diff --git a/block.c b/block.c
index c26a9f8..a67b9b6 100644
--- a/block.c
+++ b/block.c
@@ -148,7 +148,6 @@ static void bdrv_block_timer(void *opaque)
void bdrv_io_limits_enable(BlockDriverState *bs)
{
- qemu_co_queue_init(&bs->throttled_reqs);
bs->block_timer = qemu_new_timer_ns(vm_clock, bdrv_block_timer, bs);
bs->io_limits_enabled = true;
}
@@ -306,6 +305,7 @@ BlockDriverState *bdrv_new(const char *device_name)
bdrv_iostatus_disable(bs);
notifier_list_init(&bs->close_notifiers);
notifier_with_return_list_init(&bs->before_write_notifiers);
+ qemu_co_queue_init(&bs->throttled_reqs);
return bs;
}
@@ -1413,6 +1413,35 @@ void bdrv_close_all(void)
}
}
+/* Check if any requests are in-flight (including throttled requests) */
+static bool bdrv_requests_pending(BlockDriverState *bs)
+{
+ if (!QLIST_EMPTY(&bs->tracked_requests)) {
+ return true;
+ }
+ if (!qemu_co_queue_empty(&bs->throttled_reqs)) {
+ return true;
+ }
+ if (bs->file && bdrv_requests_pending(bs->file)) {
+ return true;
+ }
+ if (bs->backing_hd && bdrv_requests_pending(bs->backing_hd)) {
+ return true;
+ }
+ return false;
+}
+
+static bool bdrv_requests_pending_all(void)
+{
+ BlockDriverState *bs;
+ QTAILQ_FOREACH(bs, &bdrv_states, list) {
+ if (bdrv_requests_pending(bs)) {
+ return true;
+ }
+ }
+ return false;
+}
+
/*
* Wait for pending requests to complete across all BlockDriverStates
*
@@ -1427,27 +1456,22 @@ void bdrv_close_all(void)
*/
void bdrv_drain_all(void)
{
+ /* Always run first iteration so any pending completion BHs run */
+ bool busy = true;
BlockDriverState *bs;
- bool busy;
-
- do {
- busy = qemu_aio_wait();
+ while (busy) {
/* FIXME: We do not have timer support here, so this is effectively
* a busy wait.
*/
QTAILQ_FOREACH(bs, &bdrv_states, list) {
if (!qemu_co_queue_empty(&bs->throttled_reqs)) {
qemu_co_queue_restart_all(&bs->throttled_reqs);
- busy = true;
}
}
- } while (busy);
- /* If requests are still pending there is a bug somewhere */
- QTAILQ_FOREACH(bs, &bdrv_states, list) {
- assert(QLIST_EMPTY(&bs->tracked_requests));
- assert(qemu_co_queue_empty(&bs->throttled_reqs));
+ busy = bdrv_requests_pending_all();
+ busy |= aio_poll(qemu_get_aio_context(), busy);
}
}
--
1.8.1.4
- [Qemu-devel] [PATCH v5 00/18] aio: drop io_flush(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 01/18] block: ensure bdrv_drain_all() works during bdrv_delete(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 02/18] block: stop relying on io_flush() in bdrv_drain_all(),
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v5 03/18] dataplane/virtio-blk: check exit conditions before aio_poll(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 04/18] tests: adjust test-aio to new aio_poll() semantics, Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 05/18] tests: adjust test-thread-pool to new aio_poll() semantics, Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 17/18] tests: drop event_active_cb(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 15/18] dataplane/virtio-blk: drop flush_true() and flush_io(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 06/18] aio: stop using .io_flush(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 09/18] block/iscsi: drop iscsi_process_flush(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 16/18] thread-pool: drop thread_pool_active(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 07/18] block/curl: drop curl_aio_flush(), Stefan Hajnoczi, 2013/07/01
- [Qemu-devel] [PATCH v5 11/18] block/nbd: drop nbd_have_request(), Stefan Hajnoczi, 2013/07/01