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    Subject[patch 61/67] invalidate_inode_pages2(): ignore page refcounts

    -stable review patch. If anyone has any objections, please let us know.

    ------------------
    From: Andrew Morton <akpm@osdl.org>

    The recent fix to invalidate_inode_pages() (git commit 016eb4a) managed to
    unfix invalidate_inode_pages2().

    The problem is that various bits of code in the kernel can take transient refs
    on pages: the page scanner will do this when inspecting a batch of pages, and
    the lru_cache_add() batching pagevecs also hold a ref.

    Net result is transient failures in invalidate_inode_pages2(). This affects
    NFS directory invalidation (observed) and presumably also block-backed
    direct-io (not yet reported).

    Fix it by reverting invalidate_inode_pages2() back to the old version which
    ignores the page refcounts.

    We may come up with something more clever later, but for now we need a 2.6.18
    fix for NFS.

    Cc: Chuck Lever <cel@citi.umich.edu>
    Cc: Nick Piggin <nickpiggin@yahoo.com.au>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    mm/truncate.c | 34 ++++++++++++++++++++++++++++++++--
    1 file changed, 32 insertions(+), 2 deletions(-)

    --- linux-2.6.18.orig/mm/truncate.c
    +++ linux-2.6.18/mm/truncate.c
    @@ -270,9 +270,39 @@ unsigned long invalidate_inode_pages(str
    {
    return invalidate_mapping_pages(mapping, 0, ~0UL);
    }
    -
    EXPORT_SYMBOL(invalidate_inode_pages);

    +/*
    + * This is like invalidate_complete_page(), except it ignores the page's
    + * refcount. We do this because invalidate_inode_pages2() needs stronger
    + * invalidation guarantees, and cannot afford to leave pages behind because
    + * shrink_list() has a temp ref on them, or because they're transiently sitting
    + * in the lru_cache_add() pagevecs.
    + */
    +static int
    +invalidate_complete_page2(struct address_space *mapping, struct page *page)
    +{
    + if (page->mapping != mapping)
    + return 0;
    +
    + if (PagePrivate(page) && !try_to_release_page(page, 0))
    + return 0;
    +
    + write_lock_irq(&mapping->tree_lock);
    + if (PageDirty(page))
    + goto failed;
    +
    + BUG_ON(PagePrivate(page));
    + __remove_from_page_cache(page);
    + write_unlock_irq(&mapping->tree_lock);
    + ClearPageUptodate(page);
    + page_cache_release(page); /* pagecache ref */
    + return 1;
    +failed:
    + write_unlock_irq(&mapping->tree_lock);
    + return 0;
    +}
    +
    /**
    * invalidate_inode_pages2_range - remove range of pages from an address_space
    * @mapping: the address_space
    @@ -339,7 +369,7 @@ int invalidate_inode_pages2_range(struct
    }
    }
    was_dirty = test_clear_page_dirty(page);
    - if (!invalidate_complete_page(mapping, page)) {
    + if (!invalidate_complete_page2(mapping, page)) {
    if (was_dirty)
    set_page_dirty(page);
    ret = -EIO;
    --
    -
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