[PATCH] cgroup: remove incorrect check on the return value of css_alloc

[PATCH] cgroup: remove incorrect check on the return value of css_alloc

[Xiongwei Song]

The function css_alloc never return NULL, it may return normal pointer or
error codes that made by ERR_PTR, so !css is always false, we need use
IS_ERR to check it, and if this is true, we should use ERR_CAST handle it.

Signed-off-by: Xiongwei Song <sxwjean@me.com>
---
 kernel/cgroup/cgroup.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index adac5b91d2b8..a442fd9ad744 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4728,10 +4728,8 @@ static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
 	lockdep_assert_held(&cgroup_mutex);
 
 	css = ss->css_alloc(parent_css);
-	if (!css)
-		css = ERR_PTR(-ENOMEM);
 	if (IS_ERR(css))
-		return css;
+		return ERR_CAST(css);
 
 	init_and_link_css(css, ss, cgrp);
 
-- 
2.15.1

Re: [PATCH] cgroup: remove incorrect check on the return value of css_alloc

[Tejun Heo]

Hello,

On Mon, Jan 22, 2018 at 09:38:51PM +0800, Xiongwei Song wrote:
> The function css_alloc never return NULL, it may return normal pointer or

It's a calling a controller implemented method.  I'd much rather keep
the extra protection.

> error codes that made by ERR_PTR, so !css is always false, we need use
> IS_ERR to check it, and if this is true, we should use ERR_CAST handle it.

It's of the same type.  Why would it need casting?

Thanks.

-- 
tejun

Re: [PATCH] cgroup: remove incorrect check on the return value of css_alloc

[Xiongwei Song]

> On 22 Jan 2018, at 11:55 PM, Tejun Heo <tj@kernel.org> wrote:
> 
> Hello,
> 
> On Mon, Jan 22, 2018 at 09:38:51PM +0800, Xiongwei Song wrote:
>> The function css_alloc never return NULL, it may return normal pointer or
> 
> It's a calling a controller implemented method.  I'd much rather keep
> the extra protection.
> 
>> error codes that made by ERR_PTR, so !css is always false, we need use
>> IS_ERR to check it, and if this is true, we should use ERR_CAST handle it.
> 
> It's of the same type.  Why would it need casting?

Okay, Thanks for your comment.

Apologies for the noise.

Thanks
Xiongwei
> 
> Thanks.
> 
> -- 
> tejun