qcow2: make more generic interface for qcow2_compress

Give explicit size both for source and destination buffers, to make it
similar with decompression path and than cleanly reuse parameter
structure for decompression threads.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/qcow2.c

@@ -3722,14 +3722,15 @@ fail:
 /*
  * qcow2_compress()
  *
- * @dest - destination buffer, at least of @size-1 bytes
+ * @dest - destination buffer, @dest_size bytes
- * @src - source buffer, @size bytes
+ * @src - source buffer, @src_size bytes
  *
  * Returns: compressed size on success
- *          -1 if compression is inefficient
+ *          -1 destination buffer is not enough to store compressed data
  *          -2 on any other error
  */
-static ssize_t qcow2_compress(void *dest, const void *src, size_t size)
+static ssize_t qcow2_compress(void *dest, size_t dest_size,
+                              const void *src, size_t src_size)
 {
     ssize_t ret;
     z_stream strm;
@@ -3744,14 +3745,14 @@ static ssize_t qcow2_compress(void *dest, const void *src, size_t size)
 
     /* strm.next_in is not const in old zlib versions, such as those used on
      * OpenBSD/NetBSD, so cast the const away */
-    strm.avail_in = size;
+    strm.avail_in = src_size;
     strm.next_in = (void *) src;
-    strm.avail_out = size - 1;
+    strm.avail_out = dest_size;
     strm.next_out = dest;
 
     ret = deflate(&strm, Z_FINISH);
     if (ret == Z_STREAM_END) {
-        ret = size - 1 - strm.avail_out;
+        ret = dest_size - strm.avail_out;
     } else {
         ret = (ret == Z_OK ? -1 : -2);
     }
@@ -3765,8 +3766,9 @@ static ssize_t qcow2_compress(void *dest, const void *src, size_t size)
 
 typedef struct Qcow2CompressData {
     void *dest;
+    size_t dest_size;
     const void *src;
-    size_t size;
+    size_t src_size;
     ssize_t ret;
 } Qcow2CompressData;
 
@@ -3774,7 +3776,8 @@ static int qcow2_compress_pool_func(void *opaque)
 {
     Qcow2CompressData *data = opaque;
 
-    data->ret = qcow2_compress(data->dest, data->src, data->size);
+    data->ret = qcow2_compress(data->dest, data->dest_size,
+                               data->src, data->src_size);
 
     return 0;
 }
@@ -3786,15 +3789,17 @@ static void qcow2_compress_complete(void *opaque, int ret)
 
 /* See qcow2_compress definition for parameters description */
 static ssize_t qcow2_co_compress(BlockDriverState *bs,
-                                 void *dest, const void *src, size_t size)
+                                 void *dest, size_t dest_size,
+                                 const void *src, size_t src_size)
 {
     BDRVQcow2State *s = bs->opaque;
     BlockAIOCB *acb;
     ThreadPool *pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
     Qcow2CompressData arg = {
         .dest = dest,
+        .dest_size = dest_size,
         .src = src,
-        .size = size,
+        .src_size = src_size,
     };
 
     while (s->nb_compress_threads >= MAX_COMPRESS_THREADS) {
@@ -3861,7 +3866,8 @@ qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
 
     out_buf = g_malloc(s->cluster_size);
 
-    out_len = qcow2_co_compress(bs, out_buf, buf, s->cluster_size);
+    out_len = qcow2_co_compress(bs, out_buf, s->cluster_size - 1,
+                                buf, s->cluster_size);
     if (out_len == -2) {
         ret = -EINVAL;
         goto fail;