[Qemu-devel] [RFC] block-backend: fix double inc/dec inflight requests number

[Vladimir Sementsov-Ogievskiy]

blk_co_preadv and blk_co_pwritev calls bdrv_inc_in_flight and
bdrv_dec_in_flight. But they calls correspondingly bdrv_co_preadv
and bdrv_co_pwritev, which inc/dec in-flight count by themselves.
Counting in-flight requests in blk_ layer is redundant, drop it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---

Hi all!

Is it a bug or a feature? Why do we call inc/dec twice for read/write?
We don't do this for flush and discard..

(patch is called RFC, but it may be applied as is, if it is OK)

 block/block-backend.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index baef8e7abc..8219f59d93 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1094,17 +1094,13 @@ int coroutine_fn blk_co_preadv(BlockBackend *blk, 
int64_t offset,
         return ret;
     }
 
-    bdrv_inc_in_flight(bs);
-
     /* throttling disk I/O */
     if (blk->public.throttle_group_member.throttle_state) {
         
throttle_group_co_io_limits_intercept(&blk->public.throttle_group_member,
                 bytes, false);
     }
 
-    ret = bdrv_co_preadv(blk->root, offset, bytes, qiov, flags);
-    bdrv_dec_in_flight(bs);
-    return ret;
+    return bdrv_co_preadv(blk->root, offset, bytes, qiov, flags);
 }
 
 int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
@@ -1121,7 +1117,6 @@ int coroutine_fn blk_co_pwritev(BlockBackend *blk, 
int64_t offset,
         return ret;
     }
 
-    bdrv_inc_in_flight(bs);
     /* throttling disk I/O */
     if (blk->public.throttle_group_member.throttle_state) {
         
throttle_group_co_io_limits_intercept(&blk->public.throttle_group_member,
@@ -1132,9 +1127,7 @@ int coroutine_fn blk_co_pwritev(BlockBackend *blk, 
int64_t offset,
         flags |= BDRV_REQ_FUA;
     }
 
-    ret = bdrv_co_pwritev(blk->root, offset, bytes, qiov, flags);
-    bdrv_dec_in_flight(bs);
-    return ret;
+    return bdrv_co_pwritev(blk->root, offset, bytes, qiov, flags);
 }
 
 typedef struct BlkRwCo {
-- 
2.11.1