linux-kernel - Re: [PATCH 07/20] microblaze/mm/fault.c: Port OOM changes to do_page

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Date:	Fri, 30 Mar 2012 15:29:13 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Kautuk Consul <consul.kautuk@...il.com>
CC:	microblaze-uclinux@...e.uq.edu.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/20] microblaze/mm/fault.c: Port OOM changes to do_page_fault

On 03/20/2012 02:21 PM, Kautuk Consul wrote:
> Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
> (mm: retry page fault when blocking on disk transfer) and
> commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
> (x86,mm: make pagefault killable)
>
> The above commits introduced changes into the x86 pagefault handler
> for making the page fault handler retryable as well as killable.
>
> These changes reduce the mmap_sem hold time, which is crucial
> during OOM killer invocation.
>
> Port these changes to microblaze.
>
> Signed-off-by: Kautuk Consul<consul.kautuk@...il.com>
> ---
>   arch/microblaze/mm/fault.c |   33 ++++++++++++++++++++++++++++-----
>   1 files changed, 28 insertions(+), 5 deletions(-)
>
> diff --git a/arch/microblaze/mm/fault.c b/arch/microblaze/mm/fault.c
> index ae97d2c..60e19e6 100644
> --- a/arch/microblaze/mm/fault.c
> +++ b/arch/microblaze/mm/fault.c
> @@ -93,6 +93,8 @@ void do_page_fault(struct pt_regs *regs, unsigned long address,
>   	int code = SEGV_MAPERR;
>   	int is_write = error_code&  ESR_S;
>   	int fault;
> +	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
> +					 (is_write ? FAULT_FLAG_WRITE : 0);
>
>   	regs->ear = address;
>   	regs->esr = error_code;
> @@ -139,6 +141,7 @@ void do_page_fault(struct pt_regs *regs, unsigned long address,
>   		if (kernel_mode(regs)&&  !search_exception_tables(regs->pc))
>   			goto bad_area_nosemaphore;
>
> +retry:
>   		down_read(&mm->mmap_sem);
>   	}
>
> @@ -211,7 +214,11 @@ good_area:
>   	 * make sure we exit gracefully rather than endlessly redo
>   	 * the fault.
>   	 */
> -	fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
> +	fault = handle_mm_fault(mm, vma, address, flags);
> +
> +	if ((fault&  VM_FAULT_RETRY)&&  fatal_signal_pending(current))
> +		return;
> +
>   	if (unlikely(fault&  VM_FAULT_ERROR)) {
>   		if (fault&  VM_FAULT_OOM)
>   			goto out_of_memory;
> @@ -219,11 +226,27 @@ good_area:
>   			goto do_sigbus;
>   		BUG();
>   	}
> -	if (unlikely(fault&  VM_FAULT_MAJOR))
> -		current->maj_flt++;
> -	else
> -		current->min_flt++;
> +
> +	if (flags&  FAULT_FLAG_ALLOW_RETRY) {
> +		if (unlikely(fault&  VM_FAULT_MAJOR))
> +			current->maj_flt++;
> +		else
> +			current->min_flt++;
> +		if (fault&  VM_FAULT_RETRY) {
> +			flags&= ~FAULT_FLAG_ALLOW_RETRY;
> +
> +			/*
> +			 * No need to up_read(&mm->mmap_sem) as we would
> +			 * have already released it in __lock_page_or_retry
> +			 * in mm/filemap.c.
> +			 */
> +
> +			goto retry;
> +		}
> +	}
> +
>   	up_read(&mm->mmap_sem);
> +
>   	/*
>   	 * keep track of tlb+htab misses that are good addrs but
>   	 * just need pte's created via handle_mm_fault()

it is fine.

Acked-by: Michal Simek <monstr@...str.eu>

If this patch should go through my tree, please let me know.

Thanks,
Michal



-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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