[Qemu-devel] [PULL 1/4] nbd/server: Fix blockstatus trace

[Eric Blake <eblake@redhat.com>]

Don't increment remaining_bytes until we know that we will actually be
including the current block status extent in the reply; otherwise, the
value traced will include a bytes value that is oversized by the
length of the next block status extent which did not get sent because
it instead ended the loop.

Fixes: fb7afc79
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190403030526.12258-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 nbd/server.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/nbd/server.c b/nbd/server.c
index 218a2aa5e65..1b8c8619896 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1880,17 +1880,12 @@ static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset,

         flags = (ret & BDRV_BLOCK_ALLOCATED ? 0 : NBD_STATE_HOLE) |
                 (ret & BDRV_BLOCK_ZERO      ? NBD_STATE_ZERO : 0);
-        offset += num;
-        remaining_bytes -= num;

         if (first_extent) {
             extent->flags = flags;
             extent->length = num;
             first_extent = false;
-            continue;
-        }
-
-        if (flags == extent->flags) {
+        } else if (flags == extent->flags) {
             /* extend current extent */
             extent->length += num;
         } else {
@@ -1903,6 +1898,8 @@ static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset,
             extent->flags = flags;
             extent->length = num;
         }
+        offset += num;
+        remaining_bytes -= num;
     }

     extents_end = extent + 1;
-- 
2.20.1