block: Use g_new() & friends where that makes obvious sense

g_new(T, n) is neater than g_malloc(sizeof(T) * n).  It's also safer,
for two reasons.  One, it catches multiplication overflowing size_t.
Two, it returns T * rather than void *, which lets the compiler catch
more type errors.

Patch created with Coccinelle, with two manual changes on top:

* Add const to bdrv_iterate_format() to keep the types straight

* Convert the allocation in bdrv_drop_intermediate(), which Coccinelle
  inexplicably misses

Coccinelle semantic patch:

    @@
    type T;
    @@
    -g_malloc(sizeof(T))
    +g_new(T, 1)
    @@
    type T;
    @@
    -g_try_malloc(sizeof(T))
    +g_try_new(T, 1)
    @@
    type T;
    @@
    -g_malloc0(sizeof(T))
    +g_new0(T, 1)
    @@
    type T;
    @@
    -g_try_malloc0(sizeof(T))
    +g_try_new0(T, 1)
    @@
    type T;
    expression n;
    @@
    -g_malloc(sizeof(T) * (n))
    +g_new(T, n)
    @@
    type T;
    expression n;
    @@
    -g_try_malloc(sizeof(T) * (n))
    +g_try_new(T, n)
    @@
    type T;
    expression n;
    @@
    -g_malloc0(sizeof(T) * (n))
    +g_new0(T, n)
    @@
    type T;
    expression n;
    @@
    -g_try_malloc0(sizeof(T) * (n))
    +g_try_new0(T, n)
    @@
    type T;
    expression p, n;
    @@
    -g_realloc(p, sizeof(T) * (n))
    +g_renew(T, p, n)
    @@
    type T;
    expression p, n;
    @@
    -g_try_realloc(p, sizeof(T) * (n))
    +g_try_renew(T, p, n)

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block-migration.c b/block-migration.c
index ba3ed36..3ad31a2 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -283,7 +283,7 @@
         nr_sectors = total_sectors - cur_sector;
     }
 
-    blk = g_malloc(sizeof(BlkMigBlock));
+    blk = g_new(BlkMigBlock, 1);
     blk->buf = g_malloc(BLOCK_SIZE);
     blk->bmds = bmds;
     blk->sector = cur_sector;
@@ -354,7 +354,7 @@
             return;
         }
 
-        bmds = g_malloc0(sizeof(BlkMigDevState));
+        bmds = g_new0(BlkMigDevState, 1);
         bmds->bs = bs;
         bmds->bulk_completed = 0;
         bmds->total_sectors = sectors;
@@ -465,7 +465,7 @@
             } else {
                 nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
             }
-            blk = g_malloc(sizeof(BlkMigBlock));
+            blk = g_new(BlkMigBlock, 1);
             blk->buf = g_malloc(BLOCK_SIZE);
             blk->bmds = bmds;
             blk->sector = sector;