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    Subject[PATCHv4 12/39] thp, mm: rewrite add_to_page_cache_locked() to support huge pages
    Date
    From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

    For huge page we add to radix tree HPAGE_CACHE_NR pages at once: head
    page for the specified index and HPAGE_CACHE_NR-1 tail pages for
    following indexes.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    mm/filemap.c | 71 ++++++++++++++++++++++++++++++++++++++--------------------
    1 file changed, 47 insertions(+), 24 deletions(-)

    diff --git a/mm/filemap.c b/mm/filemap.c
    index 61158ac..b0c7c8c 100644
    --- a/mm/filemap.c
    +++ b/mm/filemap.c
    @@ -460,39 +460,62 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
    pgoff_t offset, gfp_t gfp_mask)
    {
    int error;
    + int i, nr;

    VM_BUG_ON(!PageLocked(page));
    VM_BUG_ON(PageSwapBacked(page));

    + /* memory cgroup controller handles thp pages on its side */
    error = mem_cgroup_cache_charge(page, current->mm,
    gfp_mask & GFP_RECLAIM_MASK);
    if (error)
    - goto out;
    -
    - error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
    - if (error == 0) {
    - page_cache_get(page);
    - page->mapping = mapping;
    - page->index = offset;
    + return error;

    - 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 (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE)) {
    + BUILD_BUG_ON(HPAGE_CACHE_NR > RADIX_TREE_PRELOAD_NR);
    + nr = hpage_nr_pages(page);
    + } else {
    + BUG_ON(PageTransHuge(page));
    + nr = 1;
    + }
    + error = radix_tree_preload_count(nr, gfp_mask & ~__GFP_HIGHMEM);
    + if (error) {
    mem_cgroup_uncharge_cache_page(page);
    -out:
    + return error;
    + }
    +
    + spin_lock_irq(&mapping->tree_lock);
    + for (i = 0; i < nr; i++) {
    + page_cache_get(page + i);
    + page[i].index = offset + i;
    + page[i].mapping = mapping;
    + error = radix_tree_insert(&mapping->page_tree,
    + offset + i, page + i);
    + if (error)
    + goto err;
    + }
    + __mod_zone_page_state(page_zone(page), NR_FILE_PAGES, nr);
    + if (PageTransHuge(page))
    + __inc_zone_page_state(page, NR_FILE_TRANSPARENT_HUGEPAGES);
    + mapping->nrpages += nr;
    + spin_unlock_irq(&mapping->tree_lock);
    + radix_tree_preload_end();
    + trace_mm_filemap_add_to_page_cache(page);
    + return 0;
    +err:
    + if (i != 0)
    + error = -ENOSPC; /* no space for a huge page */
    + page_cache_release(page + i);
    + page[i].mapping = NULL;
    + for (i--; i >= 0; i--) {
    + /* Leave page->index set: truncation relies upon it */
    + page[i].mapping = NULL;
    + radix_tree_delete(&mapping->page_tree, offset + i);
    + page_cache_release(page + i);
    + }
    + spin_unlock_irq(&mapping->tree_lock);
    + radix_tree_preload_end();
    + mem_cgroup_uncharge_cache_page(page);
    return error;
    }
    EXPORT_SYMBOL(add_to_page_cache_locked);
    --
    1.7.10.4


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