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authorPaolo Bonzini <pbonzini@redhat.com>2012-03-30 13:17:11 +0200
committerKevin Wolf <kwolf@redhat.com>2012-04-05 14:54:40 +0200
commit3e914655f268f627ef004a8f1ea0355311b5aca6 (patch)
treed58c2d239b697aa5f7b87fd5074447317dbd8b80 /block.c
parent12bde0eed6b740787bca2c998a838b20c556d0ec (diff)
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 <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/block.c b/block.c
index 0344673bd7..16e14fa7d5 100644
--- a/block.c
+++ b/block.c
@@ -813,6 +813,9 @@ unlink_and_fail:
void bdrv_close(BlockDriverState *bs)
{
if (bs->drv) {
+ if (bs->job) {
+ block_job_cancel_sync(bs->job);
+ }
if (bs == bs_snapshots) {
bs_snapshots = NULL;
}
@@ -966,6 +969,8 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top)
void bdrv_delete(BlockDriverState *bs)
{
assert(!bs->dev);
+ assert(!bs->job);
+ assert(!bs->in_use);
/* remove from list, if necessary */
bdrv_make_anon(bs);
@@ -4095,3 +4100,14 @@ bool block_job_is_cancelled(BlockJob *job)
{
return job->cancelled;
}
+
+void block_job_cancel_sync(BlockJob *job)
+{
+ BlockDriverState *bs = job->bs;
+
+ assert(bs->job == job);
+ block_job_cancel(job);
+ while (bs->job != NULL && bs->job->busy) {
+ qemu_aio_wait();
+ }
+}