f2fs: implement a lock-free stat_show

The stat_show is just to show the current status of f2fs.
So, we can remove all the there-in locks.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/debug.c

@@ -86,7 +86,6 @@ static void update_sit_info(struct f2fs_sb_info *sbi)
 {
 	struct f2fs_stat_info *si = F2FS_STAT(sbi);
 	unsigned int blks_per_sec, hblks_per_sec, total_vblocks, bimodal, dist;
-	struct sit_info *sit_i = SIT_I(sbi);
 	unsigned int segno, vblocks;
 	int ndirty = 0;
 
@@ -94,7 +93,6 @@ static void update_sit_info(struct f2fs_sb_info *sbi)
 	total_vblocks = 0;
 	blks_per_sec = sbi->segs_per_sec * (1 << sbi->log_blocks_per_seg);
 	hblks_per_sec = blks_per_sec / 2;
-	mutex_lock(&sit_i->sentry_lock);
 	for (segno = 0; segno < TOTAL_SEGS(sbi); segno += sbi->segs_per_sec) {
 		vblocks = get_valid_blocks(sbi, segno, sbi->segs_per_sec);
 		dist = abs(vblocks - hblks_per_sec);
@@ -105,7 +103,6 @@ static void update_sit_info(struct f2fs_sb_info *sbi)
 			ndirty++;
 		}
 	}
-	mutex_unlock(&sit_i->sentry_lock);
 	dist = TOTAL_SECS(sbi) * hblks_per_sec * hblks_per_sec / 100;
 	si->bimodal = bimodal / dist;
 	if (si->dirty_count)

fs/f2fs/f2fs.h

@@ -704,11 +704,7 @@ static inline int get_blocktype_secs(struct f2fs_sb_info *sbi, int block_type)
 
 static inline block_t valid_user_blocks(struct f2fs_sb_info *sbi)
 {
-	block_t ret;
-	spin_lock(&sbi->stat_lock);
-	ret = sbi->total_valid_block_count;
-	spin_unlock(&sbi->stat_lock);
-	return ret;
+	return sbi->total_valid_block_count;
 }
 
 static inline unsigned long __bitmap_size(struct f2fs_sb_info *sbi, int flag)
@@ -804,11 +800,7 @@ static inline void dec_valid_node_count(struct f2fs_sb_info *sbi,
 
 static inline unsigned int valid_node_count(struct f2fs_sb_info *sbi)
 {
-	unsigned int ret;
-	spin_lock(&sbi->stat_lock);
-	ret = sbi->total_valid_node_count;
-	spin_unlock(&sbi->stat_lock);
-	return ret;
+	return sbi->total_valid_node_count;
 }
 
 static inline void inc_valid_inode_count(struct f2fs_sb_info *sbi)
@@ -829,11 +821,7 @@ static inline void dec_valid_inode_count(struct f2fs_sb_info *sbi)
 
 static inline unsigned int valid_inode_count(struct f2fs_sb_info *sbi)
 {
-	unsigned int ret;
-	spin_lock(&sbi->stat_lock);
-	ret = sbi->total_valid_inode_count;
-	spin_unlock(&sbi->stat_lock);
-	return ret;
+	return sbi->total_valid_inode_count;
 }
 
 static inline void f2fs_put_page(struct page *page, int unlock)

fs/f2fs/segment.h

@@ -380,26 +380,12 @@ static inline void get_sit_bitmap(struct f2fs_sb_info *sbi,
 
 static inline block_t written_block_count(struct f2fs_sb_info *sbi)
 {
-	struct sit_info *sit_i = SIT_I(sbi);
-	block_t vblocks;
-
-	mutex_lock(&sit_i->sentry_lock);
-	vblocks = sit_i->written_valid_blocks;
-	mutex_unlock(&sit_i->sentry_lock);
-
-	return vblocks;
+	return SIT_I(sbi)->written_valid_blocks;
 }
 
 static inline unsigned int free_segments(struct f2fs_sb_info *sbi)
 {
-	struct free_segmap_info *free_i = FREE_I(sbi);
-	unsigned int free_segs;
-
-	read_lock(&free_i->segmap_lock);
-	free_segs = free_i->free_segments;
-	read_unlock(&free_i->segmap_lock);
-
-	return free_segs;
+	return FREE_I(sbi)->free_segments;
 }
 
 static inline int reserved_segments(struct f2fs_sb_info *sbi)
@@ -409,14 +395,7 @@ static inline int reserved_segments(struct f2fs_sb_info *sbi)
 
 static inline unsigned int free_sections(struct f2fs_sb_info *sbi)
 {
-	struct free_segmap_info *free_i = FREE_I(sbi);
-	unsigned int free_secs;
-
-	read_lock(&free_i->segmap_lock);
-	free_secs = free_i->free_sections;
-	read_unlock(&free_i->segmap_lock);
-
-	return free_secs;
+	return FREE_I(sbi)->free_sections;
 }
 
 static inline unsigned int prefree_segments(struct f2fs_sb_info *sbi)