linux-kernel - [RFC 1/2] mm: do not ignore mapping_gfp

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Date:	Mon,  1 Jun 2015 15:00:02 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	<linux-mm@...ck.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: [RFC 1/2] mm: do not ignore mapping_gfp_mask in page cache allocation paths

page_cache_read, do_generic_file_read, __generic_file_splice_read and
__ntfs_grab_cache_pages currently ignore mapping_gfp_mask when calling
add_to_page_cache_lru which might cause recursion into fs down in the
direct reclaim path if the mapping really relies on GFP_NOFS semantic.

This doesn't seem to be the case now because page_cache_read (page fault
path) doesn't seem to suffer from the reclaim recursion issues and
do_generic_file_read and __generic_file_splice_read also shouldn't be
called under fs locks which would deadlock in the reclaim path. Anyway
it is better to obey mapping gfp mask and prevent from later breakage.

Signed-off-by: Michal Hocko <mhocko@...e.cz>
---
 fs/ntfs/file.c | 2 +-
 fs/splice.c    | 2 +-
 mm/filemap.c   | 6 ++++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index 1da9b2d184dc..568c9dbc7e61 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -422,7 +422,7 @@ static inline int __ntfs_grab_cache_pages(struct address_space *mapping,
 				}
 			}
 			err = add_to_page_cache_lru(*cached_page, mapping, index,
-					GFP_KERNEL);
+					GFP_KERNEL & mapping_gfp_mask(mapping));
 			if (unlikely(err)) {
 				if (err == -EEXIST)
 					continue;
diff --git a/fs/splice.c b/fs/splice.c
index 7d2fbb788fc5..ebd184f24e0d 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -360,7 +360,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
 				break;
 
 			error = add_to_page_cache_lru(page, mapping, index,
-						GFP_KERNEL);
+						GFP_KERNEL & mapping_gfp_mask(mapping));
 			if (unlikely(error)) {
 				page_cache_release(page);
 				if (error == -EEXIST)
diff --git a/mm/filemap.c b/mm/filemap.c
index df533a10e8c3..adfc5d2e21c8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1669,7 +1669,8 @@ static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
 			goto out;
 		}
 		error = add_to_page_cache_lru(page, mapping,
-						index, GFP_KERNEL);
+						index,
+						GFP_KERNEL & mapping_gfp_mask(mapping));
 		if (error) {
 			page_cache_release(page);
 			if (error == -EEXIST) {
@@ -1770,7 +1771,8 @@ static int page_cache_read(struct file *file, pgoff_t offset)
 		if (!page)
 			return -ENOMEM;
 
-		ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
+		ret = add_to_page_cache_lru(page, mapping, offset,
+				GFP_KERNEL & mapping_gfp_mask(mapping));
 		if (ret == 0)
 			ret = mapping->a_ops->readpage(file, page);
 		else if (ret == -EEXIST)
-- 
2.1.4

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