f2fs: introduce f2fs_balance_fs_bg for some background jobs

This patch merges some background jobs into this new function.
Signed-off-by: Changman Lee <cm224.lee@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/f2fs.h

@@ -965,6 +965,7 @@ long f2fs_compat_ioctl(struct file *, unsigned int, unsigned long);
  */
 void f2fs_set_inode_flags(struct inode *);
 struct inode *f2fs_iget(struct super_block *, unsigned long);
+int try_to_free_nats(struct f2fs_sb_info *, int);
 void update_inode(struct inode *, struct page *);
 int update_inode_page(struct inode *);
 int f2fs_write_inode(struct inode *, struct writeback_control *);
@@ -1045,6 +1046,7 @@ void destroy_node_manager_caches(void);
  * segment.c
  */
 void f2fs_balance_fs(struct f2fs_sb_info *);
+void f2fs_balance_fs_bg(struct f2fs_sb_info *);
 void invalidate_blocks(struct f2fs_sb_info *, block_t);
 void clear_prefree_segments(struct f2fs_sb_info *);
 int npages_for_summary_flush(struct f2fs_sb_info *);

fs/f2fs/gc.c

@@ -83,9 +83,8 @@ static int gc_thread_func(void *data)
 		if (f2fs_gc(sbi))
 			wait_ms = gc_th->no_gc_sleep_time;
 
-		/* balancing prefree segments */
-		if (excess_prefree_segs(sbi))
-			f2fs_sync_fs(sbi->sb, true);
+		/* balancing f2fs's metadata periodically */
+		f2fs_balance_fs_bg(sbi);
 
 	} while (!kthread_should_stop());
 	return 0;

fs/f2fs/node.c

@@ -240,7 +240,7 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
 	write_unlock(&nm_i->nat_tree_lock);
 }
 
-static int try_to_free_nats(struct f2fs_sb_info *sbi, int nr_shrink)
+int try_to_free_nats(struct f2fs_sb_info *sbi, int nr_shrink)
 {
 	struct f2fs_nm_info *nm_i = NM_I(sbi);
 
@@ -1205,12 +1205,8 @@ static int f2fs_write_node_pages(struct address_space *mapping,
 	struct f2fs_sb_info *sbi = F2FS_SB(mapping->host->i_sb);
 	long nr_to_write = wbc->nr_to_write;
 
-	/* First check balancing cached NAT entries */
-	if (try_to_free_nats(sbi, NAT_ENTRY_PER_BLOCK) ||
-				excess_prefree_segs(sbi)) {
-		f2fs_sync_fs(sbi->sb, true);
-		return 0;
-	}
+	/* balancing f2fs's metadata in background */
+	f2fs_balance_fs_bg(sbi);
 
 	/* collect a number of dirty node pages and write together */
 	if (get_pages(sbi, F2FS_DIRTY_NODES) < COLLECT_DIRTY_NODES)

fs/f2fs/segment.c

@@ -36,6 +36,14 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
 	}
 }
 
+void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
+{
+	/* check the # of cached NAT entries and prefree segments */
+	if (try_to_free_nats(sbi, NAT_ENTRY_PER_BLOCK) ||
+				excess_prefree_segs(sbi))
+		f2fs_sync_fs(sbi->sb, true);
+}
+
 static void __locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
 		enum dirty_type dirty_type)
 {