qcow2: handle_alloc(): Get rid of keep_clusters parameter

handle_alloc() is now called with the offset at which the actual new
allocation starts instead of the offset at which the whole write request
starts, part of which may already be processed.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/qcow2-cluster.c

@@ -876,12 +876,12 @@ static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset,
  *
  *  -errno: in error cases
  *
- * TODO Get rid of keep_clusters, n_start, n_end
+ * TODO Get rid of n_start, n_end
  * TODO Make *bytes actually behave as specified above
  */
 static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
     uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m,
-    int keep_clusters, int n_start, int n_end)
+    int n_start, int n_end)
 {
     BDRVQcowState *s = bs->opaque;
     int l2_index;
@@ -892,7 +892,6 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
 
     uint64_t alloc_offset;
     uint64_t alloc_cluster_offset;
-    uint64_t keep_bytes = keep_clusters * s->cluster_size;
 
     trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset,
                              *bytes);
@@ -911,14 +910,13 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
         return ret;
     }
 
-    entry = be64_to_cpu(l2_table[l2_index + keep_clusters]);
+    entry = be64_to_cpu(l2_table[l2_index]);
 
     /* For the moment, overwrite compressed clusters one by one */
     if (entry & QCOW_OFLAG_COMPRESSED) {
         nb_clusters = 1;
     } else {
-        nb_clusters = count_cow_clusters(s, nb_clusters, l2_table,
-                                         l2_index + keep_clusters);
+        nb_clusters = count_cow_clusters(s, nb_clusters, l2_table, l2_index);
     }
 
     ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
@@ -932,13 +930,8 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
     }
 
     /* Calculate start and size of allocation */
-    alloc_offset = guest_offset + keep_bytes;
-
-    if (keep_clusters == 0) {
-        alloc_cluster_offset = 0;
-    } else {
-        alloc_cluster_offset = *host_offset + keep_bytes;
-    }
+    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,
@@ -961,13 +954,13 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
          * newly allocated cluster to the end of the aread that the write
          * request actually writes to (excluding COW at the end)
          */
-        int requested_sectors = n_end - keep_clusters * s->cluster_sectors;
+        int requested_sectors = n_end;
         int avail_sectors = nb_clusters
                             << (s->cluster_bits - BDRV_SECTOR_BITS);
-        int alloc_n_start = keep_clusters == 0 ? n_start : 0;
+        int alloc_n_start = *host_offset == 0 ? n_start : 0;
         int nb_sectors = MIN(requested_sectors, avail_sectors);
 
-        if (keep_clusters == 0) {
+        if (*host_offset == 0) {
             *host_offset = alloc_cluster_offset;
         }
 
@@ -1130,9 +1123,26 @@ again:
         goto done;
     }
 
+    int alloc_n_start;
+    int alloc_n_end;
+
+    if (keep_clusters != 0) {
+        offset         = start_of_cluster(s, offset
+                                             + keep_clusters * s->cluster_size);
+        cluster_offset = start_of_cluster(s, cluster_offset
+                                             + keep_clusters * s->cluster_size);
+
+        alloc_n_start = 0;
+        alloc_n_end = n_end - keep_clusters * s->cluster_sectors;
+    } else {
+        alloc_n_start = n_start;
+        alloc_n_end = n_end;
+    }
+
     cur_bytes = nb_clusters * s->cluster_size;
+
     ret = handle_alloc(bs, offset, &cluster_offset, &cur_bytes, m,
-                       keep_clusters, n_start, n_end);
+                       alloc_n_start, alloc_n_end);
     if (ret < 0) {
         return ret;
     }

block/qcow2.h

@@ -266,6 +266,11 @@ enum {
 
 #define REFT_OFFSET_MASK 0xffffffffffffff00ULL
 
+static inline int64_t start_of_cluster(BDRVQcowState *s, int64_t offset)
+{
+    return offset & ~(s->cluster_size - 1);
+}
+
 static inline int size_to_clusters(BDRVQcowState *s, int64_t size)
 {
     return (size + (s->cluster_size - 1)) >> s->cluster_bits;