qcow2: Clean up handle_alloc()

Things can be simplified a bit now. No semantic changes.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/qcow2-cluster.c

@@ -886,7 +886,6 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
     unsigned int nb_clusters;
     int ret;
 
-    uint64_t alloc_offset;
     uint64_t alloc_cluster_offset;
 
     trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset,
@@ -928,72 +927,69 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
         return 0;
     }
 
-    /* Calculate start and size of allocation */
-    alloc_offset = guest_offset;
-    alloc_cluster_offset = *host_offset;
-
     /* Allocate, if necessary at a given offset in the image file */
-    ret = do_alloc_cluster_offset(bs, alloc_offset, &alloc_cluster_offset,
+    alloc_cluster_offset = *host_offset;
+    ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset,
                                   &nb_clusters);
     if (ret < 0) {
         goto fail;
     }
 
-    /* save info needed for meta data update */
+    /* Can't extend contiguous allocation */
-    if (nb_clusters > 0) {
+    if (nb_clusters == 0) {
-        /*
-         * requested_sectors: Number of sectors from the start of the first
-         * newly allocated cluster to the end of the (possibly shortened
-         * before) write request.
-         *
-         * avail_sectors: Number of sectors from the start of the first
-         * newly allocated to the end of the last newly allocated cluster.
-         *
-         * nb_sectors: The number of sectors from the start of the first
-         * newly allocated cluster to the end of the aread that the write
-         * request actually writes to (excluding COW at the end)
-         */
-        int requested_sectors =
-            (*bytes + offset_into_cluster(s, guest_offset))
-            >> BDRV_SECTOR_BITS;
-        int avail_sectors = nb_clusters
-                            << (s->cluster_bits - BDRV_SECTOR_BITS);
-        int alloc_n_start = offset_into_cluster(s, guest_offset)
-                            >> BDRV_SECTOR_BITS;
-        int nb_sectors = MIN(requested_sectors, avail_sectors);
-
-        if (*host_offset == 0) {
-            *host_offset = alloc_cluster_offset;
-        }
-
-        *m = g_malloc0(sizeof(**m));
-
-        **m = (QCowL2Meta) {
-            .alloc_offset   = alloc_cluster_offset,
-            .offset         = alloc_offset & ~(s->cluster_size - 1),
-            .nb_clusters    = nb_clusters,
-            .nb_available   = nb_sectors,
-
-            .cow_start = {
-                .offset     = 0,
-                .nb_sectors = alloc_n_start,
-            },
-            .cow_end = {
-                .offset     = nb_sectors * BDRV_SECTOR_SIZE,
-                .nb_sectors = avail_sectors - nb_sectors,
-            },
-        };
-        qemu_co_queue_init(&(*m)->dependent_requests);
-        QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
-
-        *bytes = MIN(*bytes, (nb_sectors * BDRV_SECTOR_SIZE)
-                             - offset_into_cluster(s, guest_offset));
-        assert(*bytes != 0);
-    } else {
         *bytes = 0;
         return 0;
     }
 
+    /*
+     * Save info needed for meta data update.
+     *
+     * requested_sectors: Number of sectors from the start of the first
+     * newly allocated cluster to the end of the (possibly shortened
+     * before) write request.
+     *
+     * avail_sectors: Number of sectors from the start of the first
+     * newly allocated to the end of the last newly allocated cluster.
+     *
+     * nb_sectors: The number of sectors from the start of the first
+     * newly allocated cluster to the end of the area that the write
+     * request actually writes to (excluding COW at the end)
+     */
+    int requested_sectors =
+        (*bytes + offset_into_cluster(s, guest_offset))
+        >> BDRV_SECTOR_BITS;
+    int avail_sectors = nb_clusters
+                        << (s->cluster_bits - BDRV_SECTOR_BITS);
+    int alloc_n_start = offset_into_cluster(s, guest_offset)
+                        >> BDRV_SECTOR_BITS;
+    int nb_sectors = MIN(requested_sectors, avail_sectors);
+
+    *host_offset = alloc_cluster_offset;
+
+    *m = g_malloc0(sizeof(**m));
+
+    **m = (QCowL2Meta) {
+        .alloc_offset   = *host_offset,
+        .offset         = start_of_cluster(s, guest_offset),
+        .nb_clusters    = nb_clusters,
+        .nb_available   = nb_sectors,
+
+        .cow_start = {
+            .offset     = 0,
+            .nb_sectors = alloc_n_start,
+        },
+        .cow_end = {
+            .offset     = nb_sectors * BDRV_SECTOR_SIZE,
+            .nb_sectors = avail_sectors - nb_sectors,
+        },
+    };
+    qemu_co_queue_init(&(*m)->dependent_requests);
+    QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
+
+    *bytes = MIN(*bytes, (nb_sectors * BDRV_SECTOR_SIZE)
+                         - offset_into_cluster(s, guest_offset));
+    assert(*bytes != 0);
+
     return 1;
 
 fail: