Revert "f2fs: use percpu_counter for # of dirty pages in inode"

This reverts commit 1beba1b3a953107c3ff5448ab4e4297db4619c76.

The perpcu_counter doesn't provide atomicity in single core and consume more
DRAM. That incurs fs_mark test failure due to ENOMEM.

Cc: stable@vger.kernel.org # 4.7+
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 8a65949..35dbab1 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -431,7 +431,7 @@
 	/* Use below internally in f2fs*/
 	unsigned long flags;		/* use to pass per-file flags */
 	struct rw_semaphore i_sem;	/* protect fi info */
-	struct percpu_counter dirty_pages;	/* # of dirty pages */
+	atomic_t dirty_pages;		/* # of dirty pages */
 	f2fs_hash_t chash;		/* hash value of given file name */
 	unsigned int clevel;		/* maximum level of given file name */
 	nid_t i_xattr_nid;		/* node id that contains xattrs */
@@ -1269,7 +1269,7 @@
 
 static inline void inode_inc_dirty_pages(struct inode *inode)
 {
-	percpu_counter_inc(&F2FS_I(inode)->dirty_pages);
+	atomic_inc(&F2FS_I(inode)->dirty_pages);
 	inc_page_count(F2FS_I_SB(inode), S_ISDIR(inode->i_mode) ?
 				F2FS_DIRTY_DENTS : F2FS_DIRTY_DATA);
 }
@@ -1285,7 +1285,7 @@
 			!S_ISLNK(inode->i_mode))
 		return;
 
-	percpu_counter_dec(&F2FS_I(inode)->dirty_pages);
+	atomic_dec(&F2FS_I(inode)->dirty_pages);
 	dec_page_count(F2FS_I_SB(inode), S_ISDIR(inode->i_mode) ?
 				F2FS_DIRTY_DENTS : F2FS_DIRTY_DATA);
 }
@@ -1295,9 +1295,9 @@
 	return atomic_read(&sbi->nr_pages[count_type]);
 }
 
-static inline s64 get_dirty_pages(struct inode *inode)
+static inline int get_dirty_pages(struct inode *inode)
 {
-	return percpu_counter_sum_positive(&F2FS_I(inode)->dirty_pages);
+	return atomic_read(&F2FS_I(inode)->dirty_pages);
 }
 
 static inline int get_blocktype_secs(struct f2fs_sb_info *sbi, int block_type)