[Qemu-devel] [PATCH 1/2] block: sync bdrv_co_get_block_status_above() with bdrv_is_allocated_above()

["Denis V. Lunev" <den@openvz.org>]

They should work very similar, covering same areas if backing store is
shorter than the image. This change is necessary for the followup patch
switching to bdrv_get_block_status_above() in mirror to avoid assert
in check_block.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Fam Zheng <famz@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Jeff Cody <jcody@redhat.com>
---
 block/io.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/block/io.c b/block/io.c
index 420944d..0422123 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1745,14 +1745,28 @@ static int64_t coroutine_fn bdrv_co_get_block_status_above(BlockDriverState *bs,
 
     assert(bs != base);
     for (p = bs; p != base; p = backing_bs(p)) {
-        ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum, file);
-        if (ret < 0 || ret & BDRV_BLOCK_ALLOCATED) {
-            break;
+        int sc;
+        ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, &sc, file);
+        if (ret < 0) {
+            return ret;
+        } else if (ret & BDRV_BLOCK_ALLOCATED) {
+            *pnum = sc;
+            return ret;
+        }
+
+        /*
+         * [sector_num, nb_sectors] is unallocated on top but intermediate
+         * might have
+         *
+         * [sector_num+x, nr_sectors] allocated.
+         */
+        if (nb_sectors > sc &&
+            (p == bs || sector_num + sc < p->total_sectors)) {
+            nb_sectors = sc;
         }
-        /* [sector_num, pnum] unallocated on this layer, which could be only
-         * the first part of [sector_num, nb_sectors].  */
-        nb_sectors = MIN(nb_sectors, *pnum);
     }
+
+    *pnum = nb_sectors;
     return ret;
 }
 
-- 
2.7.4