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    Subject[PATCH 11/22] HWPOISON: Refactor truncate to allow direct truncating of page v3
    From: Nick Piggin <npiggin@suse.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
    v3: add comments

    Signed-off-by: Nick Piggin <npiggin@suse.de>
    Signed-off-by: Andi Kleen <ak@linux.intel.com>
    ---
    include/linux/mm.h | 2 ++
    mm/truncate.c | 34 ++++++++++++++++++++++------------
    2 files changed, 24 insertions(+), 12 deletions(-)

    --- sound-2.6.orig/mm/truncate.c
    +++ sound-2.6/mm/truncate.c
    @@ -135,6 +135,26 @@ invalidate_complete_page(struct address_
    return ret;
    }

    +/*
    + * Remove one page from its pagecache mapping. The page must be locked.
    + * This does not truncate the file on disk, it performs the pagecache
    + * side of the truncate operation. Dirty data will be discarded, and
    + * concurrent page references are ignored.
    + *
    + * Generic mm/fs code cannot call this on filesystem metadata mappings
    + * because those can assume that a page reference is enough to pin the
    + * page to its mapping.
    + */
    +void 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);
    + }
    + truncate_complete_page(mapping, page);
    +}
    +
    /**
    * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
    * @mapping: mapping to truncate
    @@ -196,12 +216,7 @@ 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 +253,10 @@ 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);
    --- sound-2.6.orig/include/linux/mm.h
    +++ sound-2.6/include/linux/mm.h
    @@ -814,6 +814,8 @@ 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);

    +void 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, int write_access);
    --



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