f2fs: change GC bitmaps to apply the section granularity

This patch removes a bitmap for victim segments selected by foreground GC, and
modifies the other bitmap for victim segments selected by background GC.

1) foreground GC bitmap
 : We don't need to manage this, since we just only one previous victim section
   number instead of the whole victim history.
   The f2fs uses the victim section number in order not to allocate currently
   GC'ed section to current active logs.

2) background GC bitmap
 : This bitmap is used to avoid selecting victims repeatedly by background GCs.
   In addition, the victims are able to be selected by foreground GCs, since
   there is no need to read victim blocks during foreground GCs.

   By the fact that the foreground GC reclaims segments in a section unit, it'd
   be better to manage this bitmap based on the section granularity.
Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/checkpoint.c

@@ -748,8 +748,6 @@ void write_checkpoint(struct f2fs_sb_info *sbi, bool is_umount)
 	flush_nat_entries(sbi);
 	flush_sit_entries(sbi);
 
-	reset_victim_segmap(sbi);
-
 	/* unlock all the fs_lock[] in do_checkpoint() */
 	do_checkpoint(sbi, is_umount);
 

fs/f2fs/debug.c

@@ -153,7 +153,7 @@ static void update_mem_info(struct f2fs_sb_info *sbi)
 	/* build dirty segmap */
 	si->base_mem += sizeof(struct dirty_seglist_info);
 	si->base_mem += NR_DIRTY_TYPE * f2fs_bitmap_size(TOTAL_SEGS(sbi));
-	si->base_mem += 2 * f2fs_bitmap_size(TOTAL_SEGS(sbi));
+	si->base_mem += f2fs_bitmap_size(TOTAL_SECS(sbi));
 
 	/* buld nm */
 	si->base_mem += sizeof(struct f2fs_nm_info);

fs/f2fs/f2fs.h

@@ -410,6 +410,7 @@ struct f2fs_sb_info {
 	/* for cleaning operations */
 	struct mutex gc_mutex;			/* mutex for GC */
 	struct f2fs_gc_kthread	*gc_thread;	/* GC thread */
+	unsigned int cur_victim_sec;		/* current victim section num */
 
 	/*
 	 * for stat information.
@@ -979,7 +980,6 @@ int lookup_journal_in_cursum(struct f2fs_summary_block *,
 					int, unsigned int, int);
 void flush_sit_entries(struct f2fs_sb_info *);
 int build_segment_manager(struct f2fs_sb_info *);
-void reset_victim_segmap(struct f2fs_sb_info *);
 void destroy_segment_manager(struct f2fs_sb_info *);
 
 /*

fs/f2fs/gc.c

@@ -160,18 +160,21 @@ static unsigned int get_max_cost(struct f2fs_sb_info *sbi,
 static unsigned int check_bg_victims(struct f2fs_sb_info *sbi)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-	unsigned int segno;
+	unsigned int hint = 0;
+	unsigned int secno;
 
 	/*
 	 * If the gc_type is FG_GC, we can select victim segments
 	 * selected by background GC before.
 	 * Those segments guarantee they have small valid blocks.
 	 */
-	segno = find_next_bit(dirty_i->victim_segmap[BG_GC],
-						TOTAL_SEGS(sbi), 0);
-	if (segno < TOTAL_SEGS(sbi)) {
-		clear_bit(segno, dirty_i->victim_segmap[BG_GC]);
-		return segno;
+next:
+	secno = find_next_bit(dirty_i->victim_secmap, TOTAL_SECS(sbi), hint++);
+	if (secno < TOTAL_SECS(sbi)) {
+		if (sec_usage_check(sbi, secno))
+			goto next;
+		clear_bit(secno, dirty_i->victim_secmap);
+		return secno * sbi->segs_per_sec;
 	}
 	return NULL_SEGNO;
 }
@@ -234,7 +237,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
 	struct victim_sel_policy p;
-	unsigned int segno;
+	unsigned int secno;
 	int nsearched = 0;
 
 	p.alloc_mode = alloc_mode;
@@ -253,6 +256,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 
 	while (1) {
 		unsigned long cost;
+		unsigned int segno;
 
 		segno = find_next_bit(p.dirty_segmap,
 						TOTAL_SEGS(sbi), p.offset);
@@ -265,13 +269,11 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 			break;
 		}
 		p.offset = ((segno / p.ofs_unit) * p.ofs_unit) + p.ofs_unit;
+		secno = GET_SECNO(sbi, segno);
 
-		if (test_bit(segno, dirty_i->victim_segmap[FG_GC]))
+		if (sec_usage_check(sbi, secno))
 			continue;
-		if (gc_type == BG_GC &&
-				test_bit(segno, dirty_i->victim_segmap[BG_GC]))
-			continue;
-		if (IS_CURSEC(sbi, GET_SECNO(sbi, segno)))
+		if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
 			continue;
 
 		cost = get_gc_cost(sbi, segno, &p);
@@ -291,13 +293,14 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 	}
 got_it:
 	if (p.min_segno != NULL_SEGNO) {
-		*result = (p.min_segno / p.ofs_unit) * p.ofs_unit;
 		if (p.alloc_mode == LFS) {
-			int i;
-			for (i = 0; i < p.ofs_unit; i++)
-				set_bit(*result + i,
-					dirty_i->victim_segmap[gc_type]);
+			secno = GET_SECNO(sbi, p.min_segno);
+			if (gc_type == FG_GC)
+				sbi->cur_victim_sec = secno;
+			else
+				set_bit(secno, dirty_i->victim_secmap);
 		}
+		*result = (p.min_segno / p.ofs_unit) * p.ofs_unit;
 	}
 	mutex_unlock(&dirty_i->seglist_lock);
 
@@ -662,9 +665,11 @@ int f2fs_gc(struct f2fs_sb_info *sbi)
 	for (i = 0; i < sbi->segs_per_sec; i++)
 		do_garbage_collect(sbi, segno + i, &ilist, gc_type);
 
-	if (gc_type == FG_GC &&
-			get_valid_blocks(sbi, segno, sbi->segs_per_sec) == 0)
+	if (gc_type == FG_GC) {
+		sbi->cur_victim_sec = NULL_SEGNO;
 		nfree++;
+		WARN_ON(get_valid_blocks(sbi, segno, sbi->segs_per_sec));
+	}
 
 	if (has_not_enough_free_secs(sbi, nfree))
 		goto gc_more;

fs/f2fs/segment.c

@@ -69,8 +69,9 @@ static void __remove_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
 		if (test_and_clear_bit(segno,
 					dirty_i->dirty_segmap[dirty_type]))
 			dirty_i->nr_dirty[dirty_type]--;
-		clear_bit(segno, dirty_i->victim_segmap[FG_GC]);
-		clear_bit(segno, dirty_i->victim_segmap[BG_GC]);
+		if (get_valid_blocks(sbi, segno, sbi->segs_per_sec) == 0)
+			clear_bit(GET_SECNO(sbi, segno),
+						dirty_i->victim_secmap);
 	}
 }
 
@@ -296,13 +297,12 @@ static void write_sum_page(struct f2fs_sb_info *sbi,
 	f2fs_put_page(page, 1);
 }
 
-static unsigned int check_prefree_segments(struct f2fs_sb_info *sbi,
-					int ofs_unit, int type)
+static unsigned int check_prefree_segments(struct f2fs_sb_info *sbi, int type)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
 	unsigned long *prefree_segmap = dirty_i->dirty_segmap[PRE];
-	unsigned int segno, next_segno, i;
-	int ofs = 0;
+	unsigned int segno;
+	unsigned int ofs = 0;
 
 	/*
 	 * If there is not enough reserved sections,
@@ -318,23 +318,30 @@ static unsigned int check_prefree_segments(struct f2fs_sb_info *sbi,
 	if (IS_NODESEG(type))
 		return NULL_SEGNO;
 next:
-	segno = find_next_bit(prefree_segmap, TOTAL_SEGS(sbi), ofs++);
-	ofs = ((segno / ofs_unit) * ofs_unit) + ofs_unit;
+	segno = find_next_bit(prefree_segmap, TOTAL_SEGS(sbi), ofs);
+	ofs += sbi->segs_per_sec;
+
 	if (segno < TOTAL_SEGS(sbi)) {
+		int i;
+
 		/* skip intermediate segments in a section */
-		if (segno % ofs_unit)
+		if (segno % sbi->segs_per_sec)
 			goto next;
 
-		/* skip if whole section is not prefree */
-		next_segno = find_next_zero_bit(prefree_segmap,
-						TOTAL_SEGS(sbi), segno + 1);
-		if (next_segno - segno < ofs_unit)
+		/* skip if the section is currently used */
+		if (sec_usage_check(sbi, GET_SECNO(sbi, segno)))
 			goto next;
 
+		/* skip if whole section is not prefree */
+		for (i = 1; i < sbi->segs_per_sec; i++)
+			if (!test_bit(segno + i, prefree_segmap))
+				goto next;
+
 		/* skip if whole section was not free at the last checkpoint */
-		for (i = 0; i < ofs_unit; i++)
-			if (get_seg_entry(sbi, segno)->ckpt_valid_blocks)
+		for (i = 0; i < sbi->segs_per_sec; i++)
+			if (get_seg_entry(sbi, segno + i)->ckpt_valid_blocks)
 				goto next;
+
 		return segno;
 	}
 	return NULL_SEGNO;
@@ -561,15 +568,13 @@ static void allocate_segment_by_default(struct f2fs_sb_info *sbi,
 						int type, bool force)
 {
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
-	unsigned int ofs_unit;
 
 	if (force) {
 		new_curseg(sbi, type, true);
 		goto out;
 	}
 
-	ofs_unit = need_SSR(sbi) ? 1 : sbi->segs_per_sec;
-	curseg->next_segno = check_prefree_segments(sbi, ofs_unit, type);
+	curseg->next_segno = check_prefree_segments(sbi, type);
 
 	if (curseg->next_segno != NULL_SEGNO)
 		change_curseg(sbi, type, false);
@@ -1558,14 +1563,13 @@ static void init_dirty_segmap(struct f2fs_sb_info *sbi)
 	}
 }
 
-static int init_victim_segmap(struct f2fs_sb_info *sbi)
+static int init_victim_secmap(struct f2fs_sb_info *sbi)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-	unsigned int bitmap_size = f2fs_bitmap_size(TOTAL_SEGS(sbi));
+	unsigned int bitmap_size = f2fs_bitmap_size(TOTAL_SECS(sbi));
 
-	dirty_i->victim_segmap[FG_GC] = kzalloc(bitmap_size, GFP_KERNEL);
-	dirty_i->victim_segmap[BG_GC] = kzalloc(bitmap_size, GFP_KERNEL);
-	if (!dirty_i->victim_segmap[FG_GC] || !dirty_i->victim_segmap[BG_GC])
+	dirty_i->victim_secmap = kzalloc(bitmap_size, GFP_KERNEL);
+	if (!dirty_i->victim_secmap)
 		return -ENOMEM;
 	return 0;
 }
@@ -1592,7 +1596,7 @@ static int build_dirty_segmap(struct f2fs_sb_info *sbi)
 	}
 
 	init_dirty_segmap(sbi);
-	return init_victim_segmap(sbi);
+	return init_victim_secmap(sbi);
 }
 
 /*
@@ -1679,18 +1683,10 @@ static void discard_dirty_segmap(struct f2fs_sb_info *sbi,
 	mutex_unlock(&dirty_i->seglist_lock);
 }
 
-void reset_victim_segmap(struct f2fs_sb_info *sbi)
-{
-	unsigned int bitmap_size = f2fs_bitmap_size(TOTAL_SEGS(sbi));
-	memset(DIRTY_I(sbi)->victim_segmap[FG_GC], 0, bitmap_size);
-}
-
-static void destroy_victim_segmap(struct f2fs_sb_info *sbi)
+static void destroy_victim_secmap(struct f2fs_sb_info *sbi)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-
-	kfree(dirty_i->victim_segmap[FG_GC]);
-	kfree(dirty_i->victim_segmap[BG_GC]);
+	kfree(dirty_i->victim_secmap);
 }
 
 static void destroy_dirty_segmap(struct f2fs_sb_info *sbi)
@@ -1705,7 +1701,7 @@ static void destroy_dirty_segmap(struct f2fs_sb_info *sbi)
 	for (i = 0; i < NR_DIRTY_TYPE; i++)
 		discard_dirty_segmap(sbi, i);
 
-	destroy_victim_segmap(sbi);
+	destroy_victim_secmap(sbi);
 	SM_I(sbi)->dirty_info = NULL;
 	kfree(dirty_i);
 }

fs/f2fs/segment.h

@@ -10,6 +10,7 @@
  */
 /* constant macro */
 #define NULL_SEGNO			((unsigned int)(~0))
+#define NULL_SECNO			((unsigned int)(~0))
 
 /* V: Logical segment # in volume, R: Relative segment # in main area */
 #define GET_L2R_SEGNO(free_i, segno)	(segno - free_i->start_segno)
@@ -214,7 +215,7 @@ struct dirty_seglist_info {
 	unsigned long *dirty_segmap[NR_DIRTY_TYPE];
 	struct mutex seglist_lock;		/* lock for segment bitmaps */
 	int nr_dirty[NR_DIRTY_TYPE];		/* # of dirty segments */
-	unsigned long *victim_segmap[2];	/* BG_GC, FG_GC */
+	unsigned long *victim_secmap;		/* background GC victims */
 };
 
 /* victim selection function for cleaning and SSR */
@@ -616,3 +617,10 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info *sbi, int base, int type)
 		le32_to_cpu(F2FS_CKPT(sbi)->cp_pack_total_block_count)
 				- (base + 1) + type;
 }
+
+static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned int secno)
+{
+	if (IS_CURSEC(sbi, secno) || (sbi->cur_victim_sec == secno))
+		return true;
+	return false;
+}

fs/f2fs/super.c

@@ -26,6 +26,7 @@
 
 #include "f2fs.h"
 #include "node.h"
+#include "segment.h"
 #include "xattr.h"
 
 static struct kmem_cache *f2fs_inode_cachep;
@@ -458,6 +459,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
 	sbi->root_ino_num = le32_to_cpu(raw_super->root_ino);
 	sbi->node_ino_num = le32_to_cpu(raw_super->node_ino);
 	sbi->meta_ino_num = le32_to_cpu(raw_super->meta_ino);
+	sbi->cur_victim_sec = NULL_SECNO;
 
 	for (i = 0; i < NR_COUNT_TYPE; i++)
 		atomic_set(&sbi->nr_pages[i], 0);