[PATCH, RFC 07/16] thp, mm: rewrite delete_from_page_cache() to support huge pages

["Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>]

From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>

As with add_to_page_cache_locked() we handle HPAGE_CACHE_NR pages a
time.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 mm/filemap.c |   27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index fa2fdab..a4b4fd5 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -112,6 +112,7 @@
 void __delete_from_page_cache(struct page *page)
 {
 	struct address_space *mapping = page->mapping;
+	int nr = 1;
 
 	/*
 	 * if we're uptodate, flush out into the cleancache, otherwise
@@ -123,13 +124,23 @@ void __delete_from_page_cache(struct page *page)
 	else
 		cleancache_invalidate_page(mapping, page);
 
-	radix_tree_delete(&mapping->page_tree, page->index);
+	if (PageTransHuge(page)) {
+		int i;
+
+		for (i = 0; i < HPAGE_CACHE_NR; i++)
+			radix_tree_delete(&mapping->page_tree, page->index + i);
+		nr = HPAGE_CACHE_NR;
+	} else {
+		radix_tree_delete(&mapping->page_tree, page->index);
+	}
+
 	page->mapping = NULL;
 	/* Leave page->index set: truncation lookup relies upon it */
-	mapping->nrpages--;
-	__dec_zone_page_state(page, NR_FILE_PAGES);
+
+	mapping->nrpages -= nr;
+	__mod_zone_page_state(page_zone(page), NR_FILE_PAGES, -nr);
 	if (PageSwapBacked(page))
-		__dec_zone_page_state(page, NR_SHMEM);
+		__mod_zone_page_state(page_zone(page), NR_SHMEM, -nr);
 	BUG_ON(page_mapped(page));
 
 	/*
@@ -140,8 +151,8 @@ void __delete_from_page_cache(struct page *page)
 	 * having removed the page entirely.
 	 */
 	if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
-		dec_zone_page_state(page, NR_FILE_DIRTY);
-		dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
+		mod_zone_page_state(page_zone(page), NR_FILE_DIRTY, -nr);
+		add_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE, -nr);
 	}
 }
 
@@ -157,6 +168,7 @@ void delete_from_page_cache(struct page *page)
 {
 	struct address_space *mapping = page->mapping;
 	void (*freepage)(struct page *);
+	int i;
 
 	BUG_ON(!PageLocked(page));
 
@@ -168,6 +180,9 @@ void delete_from_page_cache(struct page *page)
 
 	if (freepage)
 		freepage(page);
+	if (PageTransHuge(page))
+		for (i = 1; i < HPAGE_CACHE_NR; i++)
+			page_cache_release(page);
 	page_cache_release(page);
 }
 EXPORT_SYMBOL(delete_from_page_cache);
-- 
1.7.10.4

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