From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42458) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UnSQR-0001pA-HB for qemu-devel@nongnu.org; Fri, 14 Jun 2013 07:44:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UnSQO-0006qy-Jo for qemu-devel@nongnu.org; Fri, 14 Jun 2013 07:44:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16647) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UnSQO-0006qs-Bl for qemu-devel@nongnu.org; Fri, 14 Jun 2013 07:44:12 -0400 From: Stefan Hajnoczi Date: Fri, 14 Jun 2013 13:43:47 +0200 Message-Id: <1371210243-6099-2-git-send-email-stefanha@redhat.com> In-Reply-To: <1371210243-6099-1-git-send-email-stefanha@redhat.com> References: <1371210243-6099-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH v4 01/17] block: stop relying on io_flush() in bdrv_drain_all() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Paolo Bonzini , Anthony Liguori , Ping Fan Liu , Stefan Hajnoczi 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. In bdrv_delete() make sure to call bdrv_make_anon() *after* bdrv_close() so that the device is still seen by bdrv_drain_all() when iterating bdrv_states. Signed-off-by: Stefan Hajnoczi --- block.c | 50 +++++++++++++++++++++++++++++++++++++------------- 1 file changed, 37 insertions(+), 13 deletions(-) diff --git a/block.c b/block.c index 79ad33d..04821d8 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; } @@ -305,6 +304,7 @@ BlockDriverState *bdrv_new(const char *device_name) } bdrv_iostatus_disable(bs); notifier_list_init(&bs->close_notifiers); + qemu_co_queue_init(&bs->throttled_reqs); return bs; } @@ -1412,6 +1412,35 @@ 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 * @@ -1426,27 +1455,22 @@ 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); } } @@ -1591,11 +1615,11 @@ void bdrv_delete(BlockDriverState *bs) assert(!bs->job); assert(!bs->in_use); + bdrv_close(bs); + /* remove from list, if necessary */ bdrv_make_anon(bs); - bdrv_close(bs); - g_free(bs); } -- 1.8.1.4