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.
This change should be made very carefully. Let us assume that we have
top image and 2 backing stores L0->L1->L2.
L0: --------------
L1: -------
L2: -------=======
The data marked as '=' in L2 should not appear as BDRV_BLOCK_ALLOCATED
and we should return it as filled in L0 image with properly calculated
*pnum value.
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Stefan Hajnoczi <stefa...@redhat.com>
CC: Fam Zheng <f...@redhat.com>
CC: Kevin Wolf <kw...@redhat.com>
CC: Max Reitz <mre...@redhat.com>
CC: Jeff Cody <jc...@redhat.com>
---
block/io.c | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
diff --git a/block/io.c b/block/io.c
index 420944d..067d465 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1741,18 +1741,33 @@ static int64_t coroutine_fn
bdrv_co_get_block_status_above(BlockDriverState *bs,
BlockDriverState **file)
{
BlockDriverState *p;
- int64_t ret = 0;
+ int64_t ret = 0, res = nb_sectors;
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;
+ }
+
+ if (res > sc && (p == bs || sector_num + sc < p->total_sectors)) {
+ res = 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);
+ nb_sectors = MIN(nb_sectors, sc);
+
+ if (nb_sectors == 0) {
+ break;
+ }
}
+
+ *pnum = res;
return ret;
}
--
2.7.4
