From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47930) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YyHvl-0006B8-6E for qemu-devel@nongnu.org; Fri, 29 May 2015 06:54:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YyHvk-00075I-C4 for qemu-devel@nongnu.org; Fri, 29 May 2015 06:54:25 -0400 From: Fam Zheng Date: Fri, 29 May 2015 18:53:25 +0800 Message-Id: <1432896805-23867-13-git-send-email-famz@redhat.com> In-Reply-To: <1432896805-23867-1-git-send-email-famz@redhat.com> References: <1432896805-23867-1-git-send-email-famz@redhat.com> Subject: [Qemu-devel] [RFC PATCH 12/12] mirror: Protect source between bdrv_drain and bdrv_swap List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , fam@euphon.net, qemu-block@nongnu.org, Jeff Cody , Stefan Hajnoczi , Paolo Bonzini Source and target are in sync when we leave the mirror_run loop, they should remain so until bdrv_swap. Before block_job_defer_to_main_loop was introduced, it has been easy to prove that. Now that tricky things can happen after mirror_run returns and before mirror_exit runs, for example, ioeventfd handlers being called, or a device model timer callback submitting more I/O. So, skip the block_job_defer_to_main_loop if we're already in the main context. This is a necessary special casing until BlockBackend really honors bdrv_lock. If we're not in the main context, we rely on the notifying mechanism to do the right thing. Signed-off-by: Fam Zheng --- block/mirror.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 58f391a..24cf687 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -57,6 +57,8 @@ typedef struct MirrorBlockJob { int in_flight; int sectors_in_flight; int ret; + /* True if the source is locked by us */ + bool need_unlock; } MirrorBlockJob; typedef struct MirrorOp { @@ -358,6 +360,9 @@ static void mirror_exit(BlockJob *job, void *opaque) if (replace_aio_context) { aio_context_release(replace_aio_context); } + if (s->need_unlock) { + bdrv_unlock(s->common.bs); + } g_free(s->replaces); bdrv_unref(s->target); block_job_completed(&s->common, data->ret); @@ -521,7 +526,8 @@ static void coroutine_fn mirror_run(void *opaque) * mirror_populate runs. */ trace_mirror_before_drain(s, cnt); - bdrv_drain(bs); + bdrv_lock(bs); + s->need_unlock = true; cnt = bdrv_get_dirty_count(s->dirty_bitmap); } @@ -543,6 +549,10 @@ static void coroutine_fn mirror_run(void *opaque) s->common.cancelled = false; break; } + if (s->need_unlock) { + bdrv_unlock(bs); + s->need_unlock = false; + } last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); } @@ -565,7 +575,11 @@ immediate_exit: data = g_malloc(sizeof(*data)); data->ret = ret; - block_job_defer_to_main_loop(&s->common, mirror_exit, data); + if (bs->aio_context == qemu_get_aio_context()) { + mirror_exit(&s->common, data); + } else { + block_job_defer_to_main_loop(&s->common, mirror_exit, data); + } } static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp) -- 2.4.2