block migration: do not submit multiple AIOs for same sector (v2)

An old version of this patch was applied to master, so this contains the
differences between v1 and v2.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block-migration.c

@@ -146,8 +146,7 @@ static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
 {
     int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
 
-    if (bmds->aio_bitmap &&
-        (sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
+    if ((sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
         return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
             (1UL << (chunk % (sizeof(unsigned long) * 8))));
     } else {
@@ -169,13 +168,9 @@ static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,
         bit = start % (sizeof(unsigned long) * 8);
         val = bmds->aio_bitmap[idx];
         if (set) {
-            if (!(val & (1UL << bit))) {
-                val |= 1UL << bit;
-            }
+            val |= 1UL << bit;
         } else {
-            if (val & (1UL << bit)) {
-                val &= ~(1UL << bit);
-            }
+            val &= ~(1UL << bit);
         }
         bmds->aio_bitmap[idx] = val;
     }
@@ -385,8 +380,9 @@ static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,
     int nr_sectors;
 
     for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {
-        if (bmds_aio_inflight(bmds, sector))
+        if (bmds_aio_inflight(bmds, sector)) {
             qemu_aio_flush();
+        }
         if (bdrv_get_dirty(bmds->bs, sector)) {
 
             if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {