multifd: Delete useless operation

We are dividing by page_size to multiply again in the only use.
Once there, improve the comments.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/multifd-zlib.c

@@ -42,7 +42,6 @@ struct zlib_data {
  */
 static int zlib_send_setup(MultiFDSendParams *p, Error **errp)
 {
-    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     struct zlib_data *z = g_malloc0(sizeof(struct zlib_data));
     z_stream *zs = &z->zs;
 
@@ -54,9 +53,8 @@ static int zlib_send_setup(MultiFDSendParams *p, Error **errp)
         error_setg(errp, "multifd %d: deflate init failed", p->id);
         return -1;
     }
-    /* We will never have more than page_count pages */
-    z->zbuff_len = page_count * qemu_target_page_size();
-    z->zbuff_len *= 2;
+    /* To be safe, we reserve twice the size of the packet */
+    z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         deflateEnd(&z->zs);
@@ -180,7 +178,6 @@ static int zlib_send_write(MultiFDSendParams *p, uint32_t used, Error **errp)
  */
 static int zlib_recv_setup(MultiFDRecvParams *p, Error **errp)
 {
-    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     struct zlib_data *z = g_malloc0(sizeof(struct zlib_data));
     z_stream *zs = &z->zs;
 
@@ -194,10 +191,8 @@ static int zlib_recv_setup(MultiFDRecvParams *p, Error **errp)
         error_setg(errp, "multifd %d: inflate init failed", p->id);
         return -1;
     }
-    /* We will never have more than page_count pages */
-    z->zbuff_len = page_count * qemu_target_page_size();
-    /* We know compression "could" use more space */
-    z->zbuff_len *= 2;
+    /* To be safe, we reserve twice the size of the packet */
+    z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         inflateEnd(zs);

migration/multifd-zstd.c

@@ -47,7 +47,6 @@ struct zstd_data {
  */
 static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
 {
-    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     struct zstd_data *z = g_new0(struct zstd_data, 1);
     int res;
 
@@ -67,9 +66,8 @@ static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
                    p->id, ZSTD_getErrorName(res));
         return -1;
     }
-    /* We will never have more than page_count pages */
-    z->zbuff_len = page_count * qemu_target_page_size();
-    z->zbuff_len *= 2;
+    /* To be safe, we reserve twice the size of the packet */
+    z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         ZSTD_freeCStream(z->zcs);
@@ -191,7 +189,6 @@ static int zstd_send_write(MultiFDSendParams *p, uint32_t used, Error **errp)
  */
 static int zstd_recv_setup(MultiFDRecvParams *p, Error **errp)
 {
-    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     struct zstd_data *z = g_new0(struct zstd_data, 1);
     int ret;
 
@@ -212,10 +209,8 @@ static int zstd_recv_setup(MultiFDRecvParams *p, Error **errp)
         return -1;
     }
 
-    /* We will never have more than page_count pages */
-    z->zbuff_len = page_count * qemu_target_page_size();
-    /* We know compression "could" use more space */
-    z->zbuff_len *= 2;
+    /* To be safe, we reserve twice the size of the packet */
+    z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         ZSTD_freeDStream(z->zds);