From 2ac01520be8717f3492b10a083c3e0e22cb52cda Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Fri, 11 Sep 2015 18:47:51 +0200 Subject: qcow2: Make qcow2_alloc_bytes() more explicit In case of -EAGAIN returned by update_refcount(), we should discard the cluster offset we were trying to allocate and request a new one, because in theory that old offset might now be taken by a refcount block. In practice, this was not the case due to update_refcount() generally returning strictly monotonic increasing cluster offsets. However, this behavior is not set in stone, and it is also not obvious when looking at qcow2_alloc_bytes() alone, so we should not rely on it. Reported-by: Kevin Wolf Signed-off-by: Max Reitz Signed-off-by: Kevin Wolf --- block/qcow2-refcount.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'block') diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index a49d59e..2110839 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -949,11 +949,17 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) if (!offset || ROUND_UP(offset, s->cluster_size) != new_cluster) { offset = new_cluster; + free_in_cluster = s->cluster_size; + } else { + free_in_cluster += s->cluster_size; } } assert(offset); ret = update_refcount(bs, offset, size, 1, false, QCOW2_DISCARD_NEVER); + if (ret < 0) { + offset = 0; + } } while (ret == -EAGAIN); if (ret < 0) { return ret; -- cgit v1.1