[v3] Add subcluster allocation to qcow2

[RFC PATCH v3 20/27] qcow2: Fix offset calculation in handle_dependencies()

Posted by Alberto Garcia 6 years, 1 month ago

l2meta_cow_start() and l2meta_cow_end() are not necessarily
cluster-aligned if the image has subclusters, so update the
calculation of old_start and old_end to guarantee that no two requests
try to write on the same cluster.

Signed-off-by: Alberto Garcia <berto@igalia.com>
---
 block/qcow2-cluster.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index ede75138d2..0a40944667 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1279,8 +1279,8 @@ static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset,
 
         uint64_t start = guest_offset;
         uint64_t end = start + bytes;
-        uint64_t old_start = l2meta_cow_start(old_alloc);
-        uint64_t old_end = l2meta_cow_end(old_alloc);
+        uint64_t old_start = start_of_cluster(s, l2meta_cow_start(old_alloc));
+        uint64_t old_end = ROUND_UP(l2meta_cow_end(old_alloc), s->cluster_size);
 
         if (end <= old_start || start >= old_end) {
             /* No intersection */
-- 
2.20.1

Re: [RFC PATCH v3 20/27] qcow2: Fix offset calculation in handle_dependencies()

Posted by Max Reitz 5 years, 11 months ago

On 22.12.19 12:37, Alberto Garcia wrote:
> l2meta_cow_start() and l2meta_cow_end() are not necessarily
> cluster-aligned if the image has subclusters, so update the
> calculation of old_start and old_end to guarantee that no two requests
> try to write on the same cluster.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>  block/qcow2-cluster.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>