[PATCH 14/14] mm: oom_kill: use IS_ERR() instead of strict checking

[PATCH 14/14] mm: oom_kill: use IS_ERR() instead of strict checking

[Kulikov Vasiliy]

From: Vasiliy Kulikov <segooon@gmail.com>

Use IS_ERR() instead of strict checking.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
---
 Compile tested.

 mm/oom_kill.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index fc81cb2..2ee3350 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -514,7 +514,7 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
 	read_lock(&tasklist_lock);
 retry:
 	p = select_bad_process(&points, limit, mem, NULL);
-	if (!p || PTR_ERR(p) == -1UL)
+	if (IS_ERR_OR_NULL(p))
 		goto out;
 
 	if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL,
@@ -691,7 +691,7 @@ retry:
 	p = select_bad_process(&points, totalpages, NULL,
 			constraint == CONSTRAINT_MEMORY_POLICY ? nodemask :
 								 NULL);
-	if (PTR_ERR(p) == -1UL)
+	if (IS_ERR(p))
 		goto out;
 
 	/* Found nothing?!?! Either we hang forever, or we panic. */
-- 
1.7.0.4

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Re: [PATCH 14/14] mm: oom_kill: use IS_ERR() instead of strict checking

[David Rientjes]

On Sun, 5 Sep 2010, Kulikov Vasiliy wrote:

> From: Vasiliy Kulikov <segooon@gmail.com>
> 
> Use IS_ERR() instead of strict checking.
> 
> Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>

Acked-by: David Rientjes <rientjes@google.com>

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Re: [PATCH 14/14] mm: oom_kill: use IS_ERR() instead of strict checking

[KOSAKI Motohiro]

> From: Vasiliy Kulikov <segooon@gmail.com>
> 
> Use IS_ERR() instead of strict checking.

Umm...

I don't like this. IS_ERR() imply an argument is error code. but in
this case, we don't use error code. -1 mean oom special purpose meaning
value.

So, if we take this direction, It would be better to use EAGAIN or something
instead -1.



> 
> Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
> ---
>  Compile tested.
> 
>  mm/oom_kill.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index fc81cb2..2ee3350 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -514,7 +514,7 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
>  	read_lock(&tasklist_lock);
>  retry:
>  	p = select_bad_process(&points, limit, mem, NULL);
> -	if (!p || PTR_ERR(p) == -1UL)
> +	if (IS_ERR_OR_NULL(p))
>  		goto out;
>  
>  	if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL,
> @@ -691,7 +691,7 @@ retry:
>  	p = select_bad_process(&points, totalpages, NULL,
>  			constraint == CONSTRAINT_MEMORY_POLICY ? nodemask :
>  								 NULL);
> -	if (PTR_ERR(p) == -1UL)
> +	if (IS_ERR(p))
>  		goto out;
>  
>  	/* Found nothing?!?! Either we hang forever, or we panic. */
> -- 
> 1.7.0.4
> 



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Re: [PATCH 14/14] mm: oom_kill: use IS_ERR() instead of strict checking

[David Rientjes]

On Mon, 6 Sep 2010, KOSAKI Motohiro wrote:

> > From: Vasiliy Kulikov <segooon@gmail.com>
> > 
> > Use IS_ERR() instead of strict checking.
> 
> Umm...
> 
> I don't like this. IS_ERR() imply an argument is error code. but in
> this case, we don't use error code. -1 mean oom special purpose meaning
> value.
> 

You could make the same argument by saying the current use of PTR_ERR() 
implies an error code.  We've simply hijacked -1UL for simplicity in this 
case and because select_bad_process() can only return one other value 
besides a pointer to a process or NULL.

> So, if we take this direction, It would be better to use EAGAIN or something
> instead -1.
> 

I agree it would probably better to return ERR_PTR(-EAGAIN) instead of 
using -1UL.

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