Re: [Nouveau] [PATCH] drm/nouveau/mmu: fix odd_ptr_err.cocci warnings (fwd)

[Karol Herbst]

Hi julia,

I think it would be better to extract the assignment out of the if
clause. Then you'll get something like this:

memory = ...;
if (IS_ERR(memory)) {
....
}

so, to answer your question: no, it isn't necessary.

On Tue, Nov 28, 2017 at 1:56 PM, Julia Lawall <julia.lawall@xxxxxxx> wrote:
> This is a false positive, but I wonder if it is really necessary to put
> the assignment in the conditional test expression.
>
> julia
>
> ---------- Forwarded message ----------
> Date: Tue, 28 Nov 2017 13:23:36 +0800
> From: kbuild test robot <fengguang.wu@xxxxxxxxx>
> To: kbuild@xxxxxx
> Cc: Julia Lawall <julia.lawall@xxxxxxx>
> Subject: [PATCH] drm/nouveau/mmu: fix odd_ptr_err.cocci warnings
>
> CC: kbuild-all@xxxxxx
> CC: linux-kernel@xxxxxxxxxxxxxxx
> TO: Ben Skeggs <bskeggs@xxxxxxxxxx>
> CC: David Airlie <airlied@xxxxxxxx>
> CC: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> CC: nouveau@xxxxxxxxxxxxxxxxxxxxx
> CC: linux-kernel@xxxxxxxxxxxxxxx
>
> drivers/gpu/drm/nouveau/nvkm/subdev/mmu/uvmm.c:109:5-11: inconsistent IS_ERR and PTR_ERR on line 110.
> drivers/gpu/drm/nouveau/nvkm/subdev/mmu/uvmm.c:109:5-11: inconsistent IS_ERR and PTR_ERR on line 111.
>
>  PTR_ERR should access the value just tested by IS_ERR
>
> Semantic patch information:
>  There can be false positives in the patch case, where it is the call to
>  IS_ERR that is wrong.
>
> Generated by: scripts/coccinelle/tests/odd_ptr_err.cocci
>
> Fixes: 920d2b5ef215 ("drm/nouveau/mmu: define user interfaces to mmu vmm opertaions")
> Signed-off-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
> ---
>
> Please take the patch only if it's a positive warning. Thanks!
>
>  uvmm.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/uvmm.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/uvmm.c
> @@ -107,8 +107,9 @@ nvkm_uvmm_mthd_map(struct nvkm_uvmm *uvm
>                 return ret;
>
>         if (IS_ERR((memory = nvkm_umem_search(client, handle)))) {
> -               VMM_DEBUG(vmm, "memory %016llx %ld\n", handle, PTR_ERR(memory));
> -               return PTR_ERR(memory);
> +               VMM_DEBUG(vmm, "memory %016llx %ld\n", handle,
> +                         PTR_ERR((memory = nvkm_umem_search(client, handle))));
> +               return PTR_ERR((memory = nvkm_umem_search(client, handle)));
>         }
>
>         mutex_lock(&vmm->mutex);
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