Subject: Re: [patch 4/4] mm, oom: remove statically defined arch functions of same name

From: Michal Hocko <[email-masked]>
Date: Wed, 14 Nov 2012 14:47:52 +0100

On Wed 14-11-12 01:15:28, David Rientjes wrote:
> out_of_memory() is a globally defined function to call the oom killer.
> x86, sh, and powerpc all use a function of the same name within file
> scope in their respective fault.c unnecessarily.  Inline the functions
> into the pagefault handlers to clean the code up.

Yes I like it. It is really confusing to have a local function with the
same name.

> 
> Cc: Ingo Molnar <[email-masked]>
> Cc: "H. Peter Anvin" <[email-masked]>
> Cc: Thomas Gleixner <[email-masked]>
> Cc: Benjamin Herrenschmidt <[email-masked]>
> Cc: Paul Mackerras <[email-masked]>
> Cc: Paul Mundt <[email-masked]>
> Signed-off-by: David Rientjes <[email-masked]>

Reviewed-by: Michal Hocko <[email-masked]>

> ---
>  arch/powerpc/mm/fault.c |   27 ++++++++++++---------------
>  arch/sh/mm/fault.c      |   19 +++++++------------
>  arch/x86/mm/fault.c     |   23 ++++++++---------------
>  3 files changed, 27 insertions(+), 42 deletions(-)
> 
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -113,19 +113,6 @@ static int store_updates_sp(struct pt_regs *regs)
>  #define MM_FAULT_CONTINUE	-1
>  #define MM_FAULT_ERR(sig)	(sig)
>  
> -static int out_of_memory(struct pt_regs *regs)
> -{
> -	/*
> -	 * We ran out of memory, or some other thing happened to us that made
> -	 * us unable to handle the page fault gracefully.
> -	 */
> -	up_read(&current->mm->mmap_sem);
> -	if (!user_mode(regs))
> -		return MM_FAULT_ERR(SIGKILL);
> -	pagefault_out_of_memory();
> -	return MM_FAULT_RETURN;
> -}
> -
>  static int do_sigbus(struct pt_regs *regs, unsigned long address)
>  {
>  	siginfo_t info;
> @@ -169,8 +156,18 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
>  		return MM_FAULT_CONTINUE;
>  
>  	/* Out of memory */
> -	if (fault & VM_FAULT_OOM)
> -		return out_of_memory(regs);
> +	if (fault & VM_FAULT_OOM) {
> +		up_read(&current->mm->mmap_sem);
> +
> +		/*
> +		 * We ran out of memory, or some other thing happened to us that
> +		 * made us unable to handle the page fault gracefully.
> +		 */
> +		if (!user_mode(regs))
> +			return MM_FAULT_ERR(SIGKILL);
> +		pagefault_out_of_memory();
> +		return MM_FAULT_RETURN;
> +	}
>  
>  	/* Bus error. x86 handles HWPOISON here, we'll add this if/when
>  	 * we support the feature in HW
> diff --git a/arch/sh/mm/fault.c b/arch/sh/mm/fault.c
> --- a/arch/sh/mm/fault.c
> +++ b/arch/sh/mm/fault.c
> @@ -301,17 +301,6 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
>  	__bad_area(regs, error_code, address, SEGV_ACCERR);
>  }
>  
> -static void out_of_memory(void)
> -{
> -	/*
> -	 * We ran out of memory, call the OOM killer, and return the userspace
> -	 * (which will retry the fault, or kill us if we got oom-killed):
> -	 */
> -	up_read(&current->mm->mmap_sem);
> -
> -	pagefault_out_of_memory();
> -}
> -
>  static void
>  do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
>  {
> @@ -353,8 +342,14 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
>  			no_context(regs, error_code, address);
>  			return 1;
>  		}
> +		up_read(&current->mm->mmap_sem);
>  
> -		out_of_memory();
> +		/*
> +		 * We ran out of memory, call the OOM killer, and return the
> +		 * userspace (which will retry the fault, or kill us if we got
> +		 * oom-killed):
> +		 */
> +		pagefault_out_of_memory();
>  	} else {
>  		if (fault & VM_FAULT_SIGBUS)
>  			do_sigbus(regs, error_code, address);
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -803,20 +803,6 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
>  	__bad_area(regs, error_code, address, SEGV_ACCERR);
>  }
>  
> -/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
> -static void
> -out_of_memory(struct pt_regs *regs, unsigned long error_code,
> -	      unsigned long address)
> -{
> -	/*
> -	 * We ran out of memory, call the OOM killer, and return the userspace
> -	 * (which will retry the fault, or kill us if we got oom-killed):
> -	 */
> -	up_read(&current->mm->mmap_sem);
> -
> -	pagefault_out_of_memory();
> -}
> -
>  static void
>  do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
>  	  unsigned int fault)
> @@ -879,7 +865,14 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
>  			return 1;
>  		}
>  
> -		out_of_memory(regs, error_code, address);
> +		up_read(&current->mm->mmap_sem);
> +
> +		/*
> +		 * We ran out of memory, call the OOM killer, and return the
> +		 * userspace (which will retry the fault, or kill us if we got
> +		 * oom-killed):
> +		 */
> +		pagefault_out_of_memory();
>  	} else {
>  		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
>  			     VM_FAULT_HWPOISON_LARGE))

-- 
Michal Hocko
SUSE Labs