From 3e914655f268f627ef004a8f1ea0355311b5aca6 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 30 Mar 2012 13:17:11 +0200 Subject: block: fix streaming/closing race Streaming can issue I/O while qcow2_close is running. This causes the L2 caches to become very confused or, alternatively, could cause a segfault when the streaming coroutine is reentered after closing its block device. The fix is to cancel streaming jobs when closing their underlying device. The cancellation must be synchronous, on the other hand qemu_aio_wait will not restart a coroutine that is sleeping in co_sleep. So add a flag saying whether streaming has in-flight I/O. If the busy flag is false, the coroutine is quiescent and, when cancelled, will not issue any new I/O. This protects streaming against closing, but not against deleting. We have a reference count protecting us against concurrent deletion, but I still added an assertion to ensure nothing bad happens. Signed-off-by: Paolo Bonzini Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/stream.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'block/stream.c') diff --git a/block/stream.c b/block/stream.c index d1b3986a8a..f186bfd4f5 100644 --- a/block/stream.c +++ b/block/stream.c @@ -175,7 +175,7 @@ retry: break; } - + s->common.busy = true; if (base) { ret = is_allocated_base(bs, base, sector_num, STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n); @@ -189,6 +189,7 @@ retry: if (s->common.speed) { uint64_t delay_ns = ratelimit_calculate_delay(&s->limit, n); if (delay_ns > 0) { + s->common.busy = false; co_sleep_ns(rt_clock, delay_ns); /* Recheck cancellation and that sectors are unallocated */ @@ -208,6 +209,7 @@ retry: /* Note that even when no rate limit is applied we need to yield * with no pending I/O here so that qemu_aio_flush() returns. */ + s->common.busy = false; co_sleep_ns(rt_clock, 0); } @@ -215,7 +217,7 @@ retry: bdrv_disable_copy_on_read(bs); } - if (sector_num == end && ret == 0) { + if (!block_job_is_cancelled(&s->common) && sector_num == end && ret == 0) { const char *base_id = NULL; if (base) { base_id = s->backing_file_id; -- cgit v1.2.1