f2fs: introduce excess_dirty_threshold()

This patch enables f2fs_balance_fs_bg() to check all metadatas' dirty
threshold rather than just checking node block's, so that checkpoint()
from background can be triggered more frequently to avoid heaping up
too much dirty metadatas.

Threshold value by default:
race with foreground ops	single type	global
No				16MB		24MB
Yes				24MB		36MB

In addtion, let f2fs_balance_fs_bg() be aware of roll-forward sapce
as well as fsync().

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: chaseyu

fs/f2fs/f2fs.h

@@ -561,6 +561,9 @@ enum {
 
 #define MAX_DIR_RA_PAGES	4	/* maximum ra pages of dir */
 
+/* dirty segments threshold for triggering CP */
+#define DEFAULT_DIRTY_THRESHOLD		4
+
 /* for in-memory extent cache entry */
 #define F2FS_MIN_EXTENT_LEN	64	/* minimum extent length */
 

fs/f2fs/node.h

@@ -138,11 +138,6 @@ static inline bool excess_cached_nats(struct f2fs_sb_info *sbi)
 	return NM_I(sbi)->nat_cnt[TOTAL_NAT] >= DEF_NAT_CACHE_THRESHOLD;
 }
 
-static inline bool excess_dirty_nodes(struct f2fs_sb_info *sbi)
-{
-	return get_pages(sbi, F2FS_DIRTY_NODES) >= sbi->blocks_per_seg * 8;
-}
-
 enum mem_type {
 	FREE_NIDS,	/* indicates the free nid list */
 	NAT_ENTRIES,	/* indicates the cached nat entry */

fs/f2fs/segment.c

@@ -529,6 +529,25 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
 	}
 }
 
+static inline bool excess_dirty_threshold(struct f2fs_sb_info *sbi)
+{
+	int factor = rwsem_is_locked(&sbi->cp_rwsem) ? 3 : 2;
+	unsigned int dents = get_pages(sbi, F2FS_DIRTY_DENTS);
+	unsigned int qdata = get_pages(sbi, F2FS_DIRTY_QDATA);
+	unsigned int nodes = get_pages(sbi, F2FS_DIRTY_NODES);
+	unsigned int meta = get_pages(sbi, F2FS_DIRTY_META);
+	unsigned int imeta = get_pages(sbi, F2FS_DIRTY_IMETA);
+	unsigned int threshold = sbi->blocks_per_seg * factor *
+					DEFAULT_DIRTY_THRESHOLD;
+	unsigned int global_threshold = threshold * 3 / 2;
+
+	if (dents >= threshold || qdata >= threshold ||
+		nodes >= threshold || meta >= threshold ||
+		imeta >= threshold)
+		return true;
+	return dents + qdata + nodes + meta + imeta >  global_threshold;
+}
+
 void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi, bool from_bg)
 {
 	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
@@ -547,8 +566,8 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi, bool from_bg)
 	else
 		f2fs_build_free_nids(sbi, false, false);
 
-	if (excess_dirty_nats(sbi) || excess_dirty_nodes(sbi) ||
-		excess_prefree_segs(sbi))
+	if (excess_dirty_nats(sbi) || excess_dirty_threshold(sbi) ||
+		excess_prefree_segs(sbi) || !f2fs_space_for_roll_forward(sbi))
 		goto do_sync;
 
 	/* there is background inflight IO or foreground operation recently */