f2fs: combine nat_bits and free_nid_bitmap cache

Both nat_bits cache and free_nid_bitmap cache provide same functionality
as a intermediate cache between free nid cache and disk, but with
different granularity of indicating free nid range, and different
persistence policy. nat_bits cache provides better persistence ability,
and free_nid_bitmap provides better granularity.

In this patch we combine advantage of both caches, so finally policy of
the intermediate cache would be:
- init: load free nid status from nat_bits into free_nid_bitmap
- lookup: scan free_nid_bitmap before load NAT blocks
- update: update free_nid_bitmap in real-time
- persistence: udpate and persist nat_bits in checkpoint

This patch also resolves performance regression reported by lkp-robot.

commit:
  4ac91242 ("f2fs: introduce free nid bitmap")
  d00030cf9cd0bb96fdccc41e33d3c91dcbb672ba ("f2fs: use __set{__clear}_bit_le")
  1382c0f3f9d3f936c8bc42ed1591cf7a593ef9f7 ("f2fs: combine nat_bits and free_nid_bitmap cache")

4ac91242 d00030cf9cd0bb96fdccc41e33 1382c0f3f9d3f936c8bc42ed15
---------------- -------------------------- --------------------------
         %stddev     %change         %stddev     %change         %stddev
             \          |                \          |                \
     77863 ±  0%      +2.1%      79485 ±  1%     +50.8%     117404 ±  0%  aim7.jobs-per-min
    231.63 ±  0%      -2.0%     227.01 ±  1%     -33.6%     153.80 ±  0%  aim7.time.elapsed_time
    231.63 ±  0%      -2.0%     227.01 ±  1%     -33.6%     153.80 ±  0%  aim7.time.elapsed_time.max
    896604 ±  0%      -0.8%     889221 ±  3%     -20.2%     715260 ±  1%  aim7.time.involuntary_context_switches
      2394 ±  1%      +4.6%       2503 ±  1%      +3.7%       2481 ±  2%  aim7.time.maximum_resident_set_size
      6240 ±  0%      -1.5%       6145 ±  1%     -14.1%       5360 ±  1%  aim7.time.system_time
   1111357 ±  3%      +1.9%    1132509 ±  2%      -6.2%    1041932 ±  2%  aim7.time.voluntary_context_switches
...
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Tested-by: Xiaolong Ye <xiaolong.ye@intel.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -338,9 +338,6 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
 		set_nat_flag(e, IS_CHECKPOINTED, false);
 	__set_nat_cache_dirty(nm_i, e);
 
-	if (enabled_nat_bits(sbi, NULL) && new_blkaddr == NEW_ADDR)
-		__clear_bit_le(NAT_BLOCK_OFFSET(ni->nid), nm_i->empty_nat_bits);
-
 	/* update fsync_mark if its inode nat entry is still alive */
 	if (ni->nid != ni->ino)
 		e = __lookup_nat_cache(nm_i, ni->ino);
@@ -1824,7 +1821,7 @@ static void remove_free_nid(struct f2fs_sb_info *sbi, nid_t nid)
 }
 
 static void update_free_nid_bitmap(struct f2fs_sb_info *sbi, nid_t nid,
-							bool set, bool build)
+			bool set, bool build, bool locked)
 {
 	struct f2fs_nm_info *nm_i = NM_I(sbi);
 	unsigned int nat_ofs = NAT_BLOCK_OFFSET(nid);
@@ -1838,11 +1835,13 @@ static void update_free_nid_bitmap(struct f2fs_sb_info *sbi, nid_t nid,
 	else
 		__clear_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
 
+	if (!locked)
 		spin_lock(&nm_i->free_nid_lock);
 	if (set)
 		nm_i->free_nid_count[nat_ofs]++;
 	else if (!build)
 		nm_i->free_nid_count[nat_ofs]--;
+	if (!locked)
 		spin_unlock(&nm_i->free_nid_lock);
 }
 
@@ -1872,7 +1871,7 @@ static void scan_nat_page(struct f2fs_sb_info *sbi,
 		f2fs_bug_on(sbi, blk_addr == NEW_ADDR);
 		if (blk_addr == NULL_ADDR)
 			freed = add_free_nid(sbi, start_nid, true);
-		update_free_nid_bitmap(sbi, start_nid, freed, true);
+		update_free_nid_bitmap(sbi, start_nid, freed, true, false);
 	}
 }
 
@@ -1920,58 +1919,6 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
 	up_read(&nm_i->nat_tree_lock);
 }
 
-static int scan_nat_bits(struct f2fs_sb_info *sbi)
-{
-	struct f2fs_nm_info *nm_i = NM_I(sbi);
-	struct page *page;
-	unsigned int i = 0;
-	nid_t nid;
-
-	if (!enabled_nat_bits(sbi, NULL))
-		return -EAGAIN;
-
-	down_read(&nm_i->nat_tree_lock);
-check_empty:
-	i = find_next_bit_le(nm_i->empty_nat_bits, nm_i->nat_blocks, i);
-	if (i >= nm_i->nat_blocks) {
-		i = 0;
-		goto check_partial;
-	}
-
-	for (nid = i * NAT_ENTRY_PER_BLOCK; nid < (i + 1) * NAT_ENTRY_PER_BLOCK;
-									nid++) {
-		if (unlikely(nid >= nm_i->max_nid))
-			break;
-		add_free_nid(sbi, nid, true);
-	}
-
-	if (nm_i->nid_cnt[FREE_NID_LIST] >= MAX_FREE_NIDS)
-		goto out;
-	i++;
-	goto check_empty;
-
-check_partial:
-	i = find_next_zero_bit_le(nm_i->full_nat_bits, nm_i->nat_blocks, i);
-	if (i >= nm_i->nat_blocks) {
-		disable_nat_bits(sbi, true);
-		up_read(&nm_i->nat_tree_lock);
-		return -EINVAL;
-	}
-
-	nid = i * NAT_ENTRY_PER_BLOCK;
-	page = get_current_nat_page(sbi, nid);
-	scan_nat_page(sbi, page, nid);
-	f2fs_put_page(page, 1);
-
-	if (nm_i->nid_cnt[FREE_NID_LIST] < MAX_FREE_NIDS) {
-		i++;
-		goto check_partial;
-	}
-out:
-	up_read(&nm_i->nat_tree_lock);
-	return 0;
-}
-
 static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
 {
 	struct f2fs_nm_info *nm_i = NM_I(sbi);
@@ -1993,21 +1940,6 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
 
 		if (nm_i->nid_cnt[FREE_NID_LIST])
 			return;
-
-		/* try to find free nids with nat_bits */
-		if (!scan_nat_bits(sbi) && nm_i->nid_cnt[FREE_NID_LIST])
-			return;
-	}
-
-	/* find next valid candidate */
-	if (enabled_nat_bits(sbi, NULL)) {
-		int idx = find_next_zero_bit_le(nm_i->full_nat_bits,
-					nm_i->nat_blocks, 0);
-
-		if (idx >= nm_i->nat_blocks)
-			set_sbi_flag(sbi, SBI_NEED_FSCK);
-		else
-			nid = idx * NAT_ENTRY_PER_BLOCK;
 	}
 
 	/* readahead nat pages to be scanned */
@@ -2094,7 +2026,7 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
 		__insert_nid_to_list(sbi, i, ALLOC_NID_LIST, false);
 		nm_i->available_nids--;
 
-		update_free_nid_bitmap(sbi, *nid, false, false);
+		update_free_nid_bitmap(sbi, *nid, false, false, false);
 
 		spin_unlock(&nm_i->nid_list_lock);
 		return true;
@@ -2150,7 +2082,7 @@ void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t nid)
 
 	nm_i->available_nids++;
 
-	update_free_nid_bitmap(sbi, nid, true, false);
+	update_free_nid_bitmap(sbi, nid, true, false, false);
 
 	spin_unlock(&nm_i->nid_list_lock);
 
@@ -2480,11 +2412,11 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 			add_free_nid(sbi, nid, false);
 			spin_lock(&NM_I(sbi)->nid_list_lock);
 			NM_I(sbi)->available_nids++;
-			update_free_nid_bitmap(sbi, nid, true, false);
+			update_free_nid_bitmap(sbi, nid, true, false, false);
 			spin_unlock(&NM_I(sbi)->nid_list_lock);
 		} else {
 			spin_lock(&NM_I(sbi)->nid_list_lock);
-			update_free_nid_bitmap(sbi, nid, false, false);
+			update_free_nid_bitmap(sbi, nid, false, false, false);
 			spin_unlock(&NM_I(sbi)->nid_list_lock);
 		}
 	}
@@ -2590,6 +2522,40 @@ static int __get_nat_bitmaps(struct f2fs_sb_info *sbi)
 	return 0;
 }
 
+inline void load_free_nid_bitmap(struct f2fs_sb_info *sbi)
+{
+	struct f2fs_nm_info *nm_i = NM_I(sbi);
+	unsigned int i = 0;
+	nid_t nid, last_nid;
+
+	if (!enabled_nat_bits(sbi, NULL))
+		return;
+
+	for (i = 0; i < nm_i->nat_blocks; i++) {
+		i = find_next_bit_le(nm_i->empty_nat_bits, nm_i->nat_blocks, i);
+		if (i >= nm_i->nat_blocks)
+			break;
+
+		__set_bit_le(i, nm_i->nat_block_bitmap);
+
+		nid = i * NAT_ENTRY_PER_BLOCK;
+		last_nid = (i + 1) * NAT_ENTRY_PER_BLOCK;
+
+		spin_lock(&nm_i->free_nid_lock);
+		for (; nid < last_nid; nid++)
+			update_free_nid_bitmap(sbi, nid, true, true, true);
+		spin_unlock(&nm_i->free_nid_lock);
+	}
+
+	for (i = 0; i < nm_i->nat_blocks; i++) {
+		i = find_next_bit_le(nm_i->full_nat_bits, nm_i->nat_blocks, i);
+		if (i >= nm_i->nat_blocks)
+			break;
+
+		__set_bit_le(i, nm_i->nat_block_bitmap);
+	}
+}
+
 static int init_node_manager(struct f2fs_sb_info *sbi)
 {
 	struct f2fs_super_block *sb_raw = F2FS_RAW_SUPER(sbi);
@@ -2691,6 +2657,9 @@ int build_node_manager(struct f2fs_sb_info *sbi)
 	if (err)
 		return err;
 
+	/* load free nid status from nat_bits table */
+	load_free_nid_bitmap(sbi);
+
 	build_free_nids(sbi, true, true);
 	return 0;
 }