f2fs: export dirty_nats_ratio in sysfs

This patch exports a new sysfs entry 'dirty_nat_ratio' to control threshold
of dirty nat entries, if current ratio exceeds configured threshold,
checkpoint will be triggered in f2fs_balance_fs_bg for flushing dirty nats.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -98,3 +98,11 @@ Date:		October 2015
 Contact:	"Chao Yu" <chao2.yu@samsung.com>
 Description:
 		 Controls the count of nid pages to be readaheaded.
+
+What:		/sys/fs/f2fs/<disk>/dirty_nats_ratio
+Date:		January 2016
+Contact:	"Chao Yu" <chao2.yu@samsung.com>
+Description:
+		 Controls dirty nat entries ratio threshold, if current
+		 ratio exceeds configured threshold, checkpoint will
+		 be triggered for flushing dirty nat entries.

fs/f2fs/f2fs.h

@@ -515,6 +515,7 @@ struct f2fs_nm_info {
 	nid_t next_scan_nid;		/* the next nid to be scanned */
 	unsigned int ram_thresh;	/* control the memory footprint */
 	unsigned int ra_nid_pages;	/* # of nid pages to be readaheaded */
+	unsigned int dirty_nats_ratio;	/* control dirty nats ratio threshold */
 
 	/* NAT cache management */
 	struct radix_tree_root nat_root;/* root of the nat entry cache */

fs/f2fs/node.c

@@ -2000,6 +2000,7 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
 	nm_i->nat_cnt = 0;
 	nm_i->ram_thresh = DEF_RAM_THRESHOLD;
 	nm_i->ra_nid_pages = DEF_RA_NID_PAGES;
+	nm_i->dirty_nats_ratio = DEF_DIRTY_NAT_RATIO_THRESHOLD;
 
 	INIT_RADIX_TREE(&nm_i->free_nid_root, GFP_ATOMIC);
 	INIT_LIST_HEAD(&nm_i->free_nid_list);

fs/f2fs/node.h

@@ -123,7 +123,7 @@ static inline void raw_nat_from_node_info(struct f2fs_nat_entry *raw_ne,
 static inline bool excess_dirty_nats(struct f2fs_sb_info *sbi)
 {
 	return NM_I(sbi)->dirty_nat_cnt >= NM_I(sbi)->max_nid *
-					DEF_DIRTY_NAT_RATIO_THRESHOLD / 100;
+					NM_I(sbi)->dirty_nats_ratio / 100;
 }
 
 enum mem_type {

fs/f2fs/super.c

@@ -216,6 +216,7 @@ F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ipu_util, min_ipu_util);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_fsync_blocks, min_fsync_blocks);
 F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, ram_thresh, ram_thresh);
 F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, ra_nid_pages, ra_nid_pages);
+F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, dirty_nats_ratio, dirty_nats_ratio);
 F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, max_victim_search, max_victim_search);
 F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, dir_level, dir_level);
 F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, cp_interval, interval_time[CP_TIME]);
@@ -237,6 +238,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(dir_level),
 	ATTR_LIST(ram_thresh),
 	ATTR_LIST(ra_nid_pages),
+	ATTR_LIST(dirty_nats_ratio),
 	ATTR_LIST(cp_interval),
 	ATTR_LIST(idle_interval),
 	NULL,