From: "Kirill A. Shutemov" <kirill.shute...@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.shute...@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 2d99191..ce1ded8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -447,39 +447,62 @@ int add_to_page_cache_locked(struct page *page, struct 
address_space *mapping,
                pgoff_t offset, gfp_t gfp_mask)
 {
        int error;
+       enum zone_stat_item item;
+       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 (PageTransHuge(page)) {
+               BUILD_BUG_ON(HPAGE_CACHE_NR > RADIX_TREE_PRELOAD_NR);
+               nr = HPAGE_CACHE_NR;
+               item = NR_FILE_TRANSPARENT_HUGEPAGES;
+       } else {
+               nr = 1;
+               item = NR_FILE_PAGES;
+       }
+       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;
+       }
+       __inc_zone_page_state(page, item);
+       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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