[PATCHv1, RFC 15/33] filemap: allocate huge page in pagecache_get_page(), if allowed

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Write path allocate pages using pagecache_get_page(). We should be able
to allocate huge pages there, if it's allowed. As usually, fallback to
small pages, if failed.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/filemap.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 566c7e6ca423..ad73b99c5ba7 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1274,13 +1274,16 @@ repeat:
 
 no_page:
 	if (!page && (fgp_flags & FGP_CREAT)) {
+		pgoff_t hoffset;
 		int err;
 		if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
 			gfp_mask |= __GFP_WRITE;
 		if (fgp_flags & FGP_NOFS)
 			gfp_mask &= ~__GFP_FS;
 
-		page = __page_cache_alloc(gfp_mask);
+		page = page_cache_alloc_huge(mapping, offset, gfp_mask);
+no_huge:	if (!page)
+			page = __page_cache_alloc(gfp_mask);
 		if (!page)
 			return NULL;
 
@@ -1291,14 +1294,24 @@ no_page:
 		if (fgp_flags & FGP_ACCESSED)
 			__SetPageReferenced(page);
 
-		err = add_to_page_cache_lru(page, mapping, offset,
+		if (PageTransHuge(page))
+			hoffset = round_down(offset, HPAGE_PMD_NR);
+		else
+			hoffset = offset;
+
+		err = add_to_page_cache_lru(page, mapping, hoffset,
 				gfp_mask & GFP_RECLAIM_MASK);
 		if (unlikely(err)) {
 			put_page(page);
+			if (PageTransHuge(page)) {
+				page = NULL;
+				goto no_huge;
+			}
 			page = NULL;
 			if (err == -EEXIST)
 				goto repeat;
 		}
+		page += offset - hoffset;
 	}
 
 	return page;
-- 
2.8.1

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