linux-kernel - [PATCH 2/2] page cache: Mask off unwanted GFP flags

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Date:   Tue, 10 Apr 2018 05:53:51 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     Matthew Wilcox <mawilcox@...rosoft.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        stable@...r.kernel.org
Subject: [PATCH 2/2] page cache: Mask off unwanted GFP flags

From: Matthew Wilcox <mawilcox@...rosoft.com>

The page cache has used the mapping's GFP flags for allocating
radix tree nodes for a long time.  It took care to always mask off the
__GFP_HIGHMEM flag, and masked off other flags in other paths, but the
__GFP_ZERO flag was still able to sneak through.  The __GFP_DMA and
__GFP_DMA32 flags would also have been able to sneak through if they
were ever used.  Fix them all by using GFP_RECLAIM_MASK at the innermost
location, and remove it from earlier in the callchain.

Fixes: 19f99cee206c ("f2fs: add core inode operations")
Reported-by: Minchan Kim <minchan@...nel.org>
Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
Cc: stable@...r.kernel.org
---
 mm/filemap.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index c2147682f4c3..1a4bfc5ed3dc 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -785,7 +785,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 	VM_BUG_ON_PAGE(!PageLocked(new), new);
 	VM_BUG_ON_PAGE(new->mapping, new);
 
-	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
+	error = radix_tree_preload(gfp_mask & GFP_RECLAIM_MASK);
 	if (!error) {
 		struct address_space *mapping = old->mapping;
 		void (*freepage)(struct page *);
@@ -841,7 +841,7 @@ static int __add_to_page_cache_locked(struct page *page,
 			return error;
 	}
 
-	error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
+	error = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK);
 	if (error) {
 		if (!huge)
 			mem_cgroup_cancel_charge(page, memcg, false);
@@ -1574,8 +1574,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
 		if (fgp_flags & FGP_ACCESSED)
 			__SetPageReferenced(page);
 
-		err = add_to_page_cache_lru(page, mapping, offset,
-				gfp_mask & GFP_RECLAIM_MASK);
+		err = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
 		if (unlikely(err)) {
 			put_page(page);
 			page = NULL;
@@ -2378,7 +2377,7 @@ static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
 		if (!page)
 			return -ENOMEM;
 
-		ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
+		ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
 		if (ret == 0)
 			ret = mapping->a_ops->readpage(file, page);
 		else if (ret == -EEXIST)
-- 
2.16.3