linux-kernel - Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

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Date:	Wed, 5 Aug 2009 12:20:08 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, fengguang.wu@...el.com,
	hidehiro.kawai.ez@...achi.com
Subject: Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

On Wed, Aug 05, 2009 at 11:36:38AM +0200, Andi Kleen wrote:
> 
> From: Nick Piggin <npiggin@...e.de>
> 
> Extract out truncate_inode_page() out of the truncate path so that
> it can be used by memory-failure.c
> 
> [AK: description, headers, fix typos]
> v2: Some white space changes from Fengguang Wu 
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> 
> ---
>  include/linux/mm.h |    2 ++
>  mm/truncate.c      |   29 +++++++++++++++--------------
>  2 files changed, 17 insertions(+), 14 deletions(-)
> 
> Index: linux/mm/truncate.c
> ===================================================================
> --- linux.orig/mm/truncate.c
> +++ linux/mm/truncate.c
> @@ -93,11 +93,11 @@ EXPORT_SYMBOL(cancel_dirty_page);
>   * its lock, b) when a concurrent invalidate_mapping_pages got there first and
>   * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
>   */
> -static void
> +static int
>  truncate_complete_page(struct address_space *mapping, struct page *page)
>  {
>  	if (page->mapping != mapping)
> -		return;
> +		return -EIO;

Hmm, at this point, the page must have been removed from pagecache,
so I don't know if you need to pass an error back?

  
>  	if (page_has_private(page))
>  		do_invalidatepage(page, 0);
> @@ -108,6 +108,7 @@ truncate_complete_page(struct address_sp
>  	remove_from_page_cache(page);
>  	ClearPageMappedToDisk(page);
>  	page_cache_release(page);	/* pagecache ref */
> +	return 0;
>  }
>  
>  /*
> @@ -135,6 +136,16 @@ invalidate_complete_page(struct address_
>  	return ret;
>  }
>  
> +int truncate_inode_page(struct address_space *mapping, struct page *page)
> +{
> +	if (page_mapped(page)) {
> +		unmap_mapping_range(mapping,
> +				   (loff_t)page->index << PAGE_CACHE_SHIFT,
> +				   PAGE_CACHE_SIZE, 0);
> +	}
> +	return truncate_complete_page(mapping, page);
> +}
> +
>  /**
>   * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
>   * @mapping: mapping to truncate
> @@ -196,12 +207,7 @@ void truncate_inode_pages_range(struct a
>  				unlock_page(page);
>  				continue;
>  			}
> -			if (page_mapped(page)) {
> -				unmap_mapping_range(mapping,
> -				  (loff_t)page_index<<PAGE_CACHE_SHIFT,
> -				  PAGE_CACHE_SIZE, 0);
> -			}
> -			truncate_complete_page(mapping, page);
> +			truncate_inode_page(mapping, page);
>  			unlock_page(page);
>  		}
>  		pagevec_release(&pvec);
> @@ -238,15 +244,10 @@ void truncate_inode_pages_range(struct a
>  				break;
>  			lock_page(page);
>  			wait_on_page_writeback(page);
> -			if (page_mapped(page)) {
> -				unmap_mapping_range(mapping,
> -				  (loff_t)page->index<<PAGE_CACHE_SHIFT,
> -				  PAGE_CACHE_SIZE, 0);
> -			}
> +			truncate_inode_page(mapping, page);
>  			if (page->index > next)
>  				next = page->index;
>  			next++;
> -			truncate_complete_page(mapping, page);
>  			unlock_page(page);
>  		}
>  		pagevec_release(&pvec);
> Index: linux/include/linux/mm.h
> ===================================================================
> --- linux.orig/include/linux/mm.h
> +++ linux/include/linux/mm.h
> @@ -809,6 +809,8 @@ static inline void unmap_shared_mapping_
>  extern int vmtruncate(struct inode * inode, loff_t offset);
>  extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
>  
> +int truncate_inode_page(struct address_space *mapping, struct page *page);
> +
>  #ifdef CONFIG_MMU
>  extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>  			unsigned long address, unsigned int flags);
--
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