Re: [Qemu-devel] [Qemu-block] [PATCH] bdrv_inc_in_flight and bdrv_dec_in_flight:

[Manos Pitsidianakis <el13635@mail.ntua.gr>]

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On Sat, Jun 10, 2017 at 03:04:10PM +0800, Zhengui Li wrote:
>Avoid empty pointer access if the bs is NULL.

Looks like most (if not all) of the places these are called dereference 
bs anyway. Can it ever be NULL? Perhaps a check for each of those case 
(if any) would be a better idea.

>Signed-off-by: Zhengui Li <lizhengui@huawei.com>
>---
> block/io.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
>diff --git a/block/io.c b/block/io.c
>index ed31810..b12d7cf 100644
>--- a/block/io.c
>+++ b/block/io.c
>@@ -492,7 +492,9 @@ static bool tracked_request_overlaps(BdrvTrackedRequest *req,
>
> void bdrv_inc_in_flight(BlockDriverState *bs)
> {
>-    atomic_inc(&bs->in_flight);
>+    if (bs) {
>+        atomic_inc(&bs->in_flight);
>+    }
> }
>
> static void dummy_bh_cb(void *opaque)
>@@ -508,8 +510,10 @@ void bdrv_wakeup(BlockDriverState *bs)
>
> void bdrv_dec_in_flight(BlockDriverState *bs)
> {
>-    atomic_dec(&bs->in_flight);
>-    bdrv_wakeup(bs);
>+    if (bs) {
>+        atomic_dec(&bs->in_flight);
>+        bdrv_wakeup(bs);
>+    }
> }
>
> static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
>-- 
>1.8.3.1
>
>
>

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