block: Fix bdrv_aligned_p*v() for qiov_offset != 0

Since these functions take a @qiov_offset, they must always take it into
account when working with @qiov.  There are a couple of places where
they do not, but they should.

Fixes: 65cd4424
       ("block/io: bdrv_aligned_preadv: use and support qiov_offset")
Fixes: 28c4da28
       ("block/io: bdrv_aligned_pwritev: use and support qiov_offset")
Reported-by: NClaudio Fontana <cfontana@suse.de>
Reported-by: NBruce Rogers <brogers@suse.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-Id: <20200728120806.265916-2-mreitz@redhat.com>
Reviewed-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Tested-by: NClaudio Fontana <cfontana@suse.de>
Tested-by: NBruce Rogers <brogers@suse.com>

block/io.c

@@ -1524,12 +1524,13 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
             assert(num);
 
             ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
-                                     num, qiov, bytes - bytes_remaining, 0);
+                                     num, qiov,
+                                     qiov_offset + bytes - bytes_remaining, 0);
             max_bytes -= num;
         } else {
             num = bytes_remaining;
-            ret = qemu_iovec_memset(qiov, bytes - bytes_remaining, 0,
-                                    bytes_remaining);
+            ret = qemu_iovec_memset(qiov, qiov_offset + bytes - bytes_remaining,
+                                    0, bytes_remaining);
         }
         if (ret < 0) {
             goto out;
@@ -2032,7 +2033,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
             }
 
             ret = bdrv_driver_pwritev(bs, offset + bytes - bytes_remaining,
-                                      num, qiov, bytes - bytes_remaining,
+                                      num, qiov,
+                                      qiov_offset + bytes - bytes_remaining,
                                       local_flags);
             if (ret < 0) {
                 break;