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    Subject[PATCH 4/8] mm: cleanup add_to_page_cache_locked()
    Date
    From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

    The patch makes add_to_page_cache_locked() cleaner:
    - unindent most code of the function by inverting one condition;
    - streamline code no-error path;
    - move insert error path outside normal code path;
    - call radix_tree_preload_end() earlier;

    No functional changes.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
    ---
    mm/filemap.c | 48 +++++++++++++++++++++++++-----------------------
    1 file changed, 25 insertions(+), 23 deletions(-)

    diff --git a/mm/filemap.c b/mm/filemap.c
    index f6fe61f..f7c4ed5 100644
    --- a/mm/filemap.c
    +++ b/mm/filemap.c
    @@ -467,32 +467,34 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
    error = mem_cgroup_cache_charge(page, current->mm,
    gfp_mask & GFP_RECLAIM_MASK);
    if (error)
    - goto out;
    + return error;

    error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
    - if (error == 0) {
    - page_cache_get(page);
    - page->mapping = mapping;
    - page->index = offset;
    -
    - spin_lock_irq(&mapping->tree_lock);
    - error = radix_tree_insert(&mapping->page_tree, offset, page);
    - if (likely(!error)) {
    - mapping->nrpages++;
    - __inc_zone_page_state(page, NR_FILE_PAGES);
    - spin_unlock_irq(&mapping->tree_lock);
    - trace_mm_filemap_add_to_page_cache(page);
    - } else {
    - page->mapping = NULL;
    - /* Leave page->index set: truncation relies upon it */
    - spin_unlock_irq(&mapping->tree_lock);
    - mem_cgroup_uncharge_cache_page(page);
    - page_cache_release(page);
    - }
    - radix_tree_preload_end();
    - } else
    + if (error) {
    mem_cgroup_uncharge_cache_page(page);
    -out:
    + return error;
    + }
    +
    + page_cache_get(page);
    + page->mapping = mapping;
    + page->index = offset;
    +
    + spin_lock_irq(&mapping->tree_lock);
    + error = radix_tree_insert(&mapping->page_tree, offset, page);
    + radix_tree_preload_end();
    + if (unlikely(!error))
    + goto err_insert;
    + mapping->nrpages++;
    + __inc_zone_page_state(page, NR_FILE_PAGES);
    + spin_unlock_irq(&mapping->tree_lock);
    + trace_mm_filemap_add_to_page_cache(page);
    + return 0;
    +err_insert:
    + page->mapping = NULL;
    + /* Leave page->index set: truncation relies upon it */
    + spin_unlock_irq(&mapping->tree_lock);
    + mem_cgroup_uncharge_cache_page(page);
    + page_cache_release(page);
    return error;
    }
    EXPORT_SYMBOL(add_to_page_cache_locked);
    --
    1.8.3.2


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