fs/buffer.c: support buffer cache allocations with gfp modifiers

commit 3b5e6454aaf6b4439b19400d8365e2ec2d24e411 upstream.

A buffer cache is allocated from movable area because it is referred
for a while and released soon.  But some filesystems are taking buffer
cache for a long time and it can disturb page migration.

New APIs are introduced to allocate buffer cache with user specific
flag.  *_gfp APIs are for user want to set page allocation flag for
page cache allocation.  And *_unmovable APIs are for the user wants to
allocate page cache from non-movable area.

Signed-off-by: Gioh Kim <gioh.kim@lge.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
[bwh: Prerequisite for "bufferhead: Add _gfp version for sb_getblk()".
 Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

1 files changed, 42 insertions, 5 deletions

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 458f497..1738420 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -166,12 +166,13 @@ void __wait_on_buffer(struct buffer_head *);
 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
 			unsigned size);
-struct buffer_head *__getblk(struct block_device *bdev, sector_t block,
-			unsigned size);
+struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
+				  unsigned size, gfp_t gfp);
 void __brelse(struct buffer_head *);
 void __bforget(struct buffer_head *);
 void __breadahead(struct block_device *, sector_t block, unsigned int size);
-struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size);
+struct buffer_head *__bread_gfp(struct block_device *,
+				sector_t block, unsigned size, gfp_t gfp);
 void invalidate_bh_lrus(void);
 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 void free_buffer_head(struct buffer_head * bh);
@@ -286,7 +287,13 @@ static inline void bforget(struct buffer_head *bh)
 static inline struct buffer_head *
 sb_bread(struct super_block *sb, sector_t block)
 {
-	return __bread(sb->s_bdev, block, sb->s_blocksize);
+	return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
+}
+
+static inline struct buffer_head *
+sb_bread_unmovable(struct super_block *sb, sector_t block)
+{
+	return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 }
 
 static inline void
@@ -298,7 +305,7 @@ sb_breadahead(struct super_block *sb, sector_t block)
 static inline struct buffer_head *
 sb_getblk(struct super_block *sb, sector_t block)
 {
-	return __getblk(sb->s_bdev, block, sb->s_blocksize);
+	return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 }
 
 static inline struct buffer_head *
@@ -335,6 +342,36 @@ static inline void lock_buffer(struct buffer_head *bh)
 		__lock_buffer(bh);
 }
 
+static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
+						   sector_t block,
+						   unsigned size)
+{
+	return __getblk_gfp(bdev, block, size, 0);
+}
+
+static inline struct buffer_head *__getblk(struct block_device *bdev,
+					   sector_t block,
+					   unsigned size)
+{
+	return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
+}
+
+/**
+ *  __bread() - reads a specified block and returns the bh
+ *  @bdev: the block_device to read from
+ *  @block: number of block
+ *  @size: size (in bytes) to read
+ *
+ *  Reads a specified block, and returns buffer head that contains it.
+ *  The page cache is allocated from movable area so that it can be migrated.
+ *  It returns NULL if the block was unreadable.
+ */
+static inline struct buffer_head *
+__bread(struct block_device *bdev, sector_t block, unsigned size)
+{
+	return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
+}
+
 extern int __set_page_dirty_buffers(struct page *page);
 
 #else /* CONFIG_BLOCK */