f2fs: use highmem for directory pages

This patch fixes to use highmem for directory pages.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/inode.c

@@ -156,7 +156,7 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
 		inode->i_op = &f2fs_dir_inode_operations;
 		inode->i_fop = &f2fs_dir_operations;
 		inode->i_mapping->a_ops = &f2fs_dblock_aops;
-		mapping_set_gfp_mask(inode->i_mapping, GFP_F2FS_ZERO);
+		mapping_set_gfp_mask(inode->i_mapping, GFP_F2FS_HIGH_ZERO);
 	} else if (S_ISLNK(inode->i_mode)) {
 		inode->i_op = &f2fs_symlink_inode_operations;
 		inode->i_mapping->a_ops = &f2fs_dblock_aops;

include/linux/f2fs_fs.h

@@ -33,7 +33,8 @@
 #define F2FS_META_INO(sbi)	(sbi->meta_ino_num)
 
 /* This flag is used by node and meta inodes, and by recovery */
-#define GFP_F2FS_ZERO	(GFP_NOFS | __GFP_ZERO)
+#define GFP_F2FS_ZERO		(GFP_NOFS | __GFP_ZERO)
+#define GFP_F2FS_HIGH_ZERO	(GFP_NOFS | __GFP_ZERO | __GFP_HIGHMEM)
 
 /*
  * For further optimization on multi-head logs, on-disk layout supports maximum