[PULL 22/27] qcow2: put discards in discard queue when discard-no-unref is enabled

[Kevin Wolf <kwolf@redhat.com>]

From: Jean-Louis Dupond <jean-louis@dupond.be>

When discard-no-unref is enabled, discards are not queued like it
should.
This was broken since discard-no-unref was added.

Add a helper function qcow2_discard_cluster which handles some common
checks and calls the queue_discards function if needed to add the
discard request to the queue.

Signed-off-by: Jean-Louis Dupond <jean-louis@dupond.be>
Message-ID: <20250513132628.1055549-3-jean-louis@dupond.be>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2.h          |  4 ++++
 block/qcow2-cluster.c  | 16 ++++++----------
 block/qcow2-refcount.c | 17 +++++++++++++++++
 3 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index a9e3481c6e..547bb2b814 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -880,6 +880,10 @@ void GRAPH_RDLOCK qcow2_free_clusters(BlockDriverState *bs,
 void GRAPH_RDLOCK
 qcow2_free_any_cluster(BlockDriverState *bs, uint64_t l2_entry,
                        enum qcow2_discard_type type);
+void GRAPH_RDLOCK
+qcow2_discard_cluster(BlockDriverState *bs, uint64_t offset,
+                      uint64_t length, QCow2ClusterType ctype,
+                      enum qcow2_discard_type dtype);
 
 int GRAPH_RDLOCK
 qcow2_update_snapshot_refcount(BlockDriverState *bs, int64_t l1_table_offset,
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index ce8c0076b3..c655bf6df4 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1978,12 +1978,10 @@ discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, uint64_t nb_clusters,
         if (!keep_reference) {
             /* Then decrease the refcount */
             qcow2_free_any_cluster(bs, old_l2_entry, type);
-        } else if (s->discard_passthrough[type] &&
-                   (cluster_type == QCOW2_CLUSTER_NORMAL ||
-                    cluster_type == QCOW2_CLUSTER_ZERO_ALLOC)) {
+        } else {
             /* If we keep the reference, pass on the discard still */
-            bdrv_pdiscard(s->data_file, old_l2_entry & L2E_OFFSET_MASK,
-                          s->cluster_size);
+            qcow2_discard_cluster(bs, old_l2_entry & L2E_OFFSET_MASK,
+                                  s->cluster_size, cluster_type, type);
         }
     }
 
@@ -2092,12 +2090,10 @@ zero_in_l2_slice(BlockDriverState *bs, uint64_t offset,
             if (!keep_reference) {
                 /* Then decrease the refcount */
                 qcow2_free_any_cluster(bs, old_l2_entry, QCOW2_DISCARD_REQUEST);
-            } else if (s->discard_passthrough[QCOW2_DISCARD_REQUEST] &&
-                       (type == QCOW2_CLUSTER_NORMAL ||
-                        type == QCOW2_CLUSTER_ZERO_ALLOC)) {
+            } else {
                 /* If we keep the reference, pass on the discard still */
-                bdrv_pdiscard(s->data_file, old_l2_entry & L2E_OFFSET_MASK,
-                            s->cluster_size);
+                qcow2_discard_cluster(bs, old_l2_entry & L2E_OFFSET_MASK,
+                            s->cluster_size, type, QCOW2_DISCARD_REQUEST);
             }
         }
     }
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 8fb210501c..6512cda407 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1205,6 +1205,23 @@ void qcow2_free_any_cluster(BlockDriverState *bs, uint64_t l2_entry,
     }
 }
 
+void qcow2_discard_cluster(BlockDriverState *bs, uint64_t offset,
+                           uint64_t length, QCow2ClusterType ctype,
+                           enum qcow2_discard_type dtype)
+{
+    BDRVQcow2State *s = bs->opaque;
+
+    if (s->discard_passthrough[dtype] &&
+        (ctype == QCOW2_CLUSTER_NORMAL ||
+         ctype == QCOW2_CLUSTER_ZERO_ALLOC)) {
+        if (has_data_file(bs)) {
+            bdrv_pdiscard(s->data_file, offset, length);
+        } else {
+            queue_discard(bs, offset, length);
+        }
+    }
+}
+
 int qcow2_write_caches(BlockDriverState *bs)
 {
     BDRVQcow2State *s = bs->opaque;
-- 
2.51.1