f2fs: support subsectional garbage collection

Section is minimal garbage collection unit of f2fs, in zoned block
device, or ancient block mapping flash device, in order to improve
GC efficiency, we can align GC unit to lower device erase unit,
normally, it consists of multiple of segments.

Once background or foreground GC triggers, it brings a large number
of IOs, which will impact user IO, and also occupy cpu/memory resource
intensively.

So, to reduce impact of GC on large size section, this patch supports
subsectional GC, in one cycle of GC, it only migrate partial segment{s}
in victim section. Currently, by default, we use sbi->segs_per_sec as
migration granularity.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 33 insertions, 6 deletions

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 84f49cb3147c..8606ebf509cb 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -333,6 +333,22 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 	if (p.max_search == 0)
 		goto out;
 
+	if (__is_large_section(sbi) && p.alloc_mode == LFS) {
+		if (sbi->next_victim_seg[BG_GC] != NULL_SEGNO) {
+			p.min_segno = sbi->next_victim_seg[BG_GC];
+			*result = p.min_segno;
+			sbi->next_victim_seg[BG_GC] = NULL_SEGNO;
+			goto got_result;
+		}
+		if (gc_type == FG_GC &&
+				sbi->next_victim_seg[FG_GC] != NULL_SEGNO) {
+			p.min_segno = sbi->next_victim_seg[FG_GC];
+			*result = p.min_segno;
+			sbi->next_victim_seg[FG_GC] = NULL_SEGNO;
+			goto got_result;
+		}
+	}
+
 	last_victim = sm->last_victim[p.gc_mode];
 	if (p.alloc_mode == LFS && gc_type == FG_GC) {
 		p.min_segno = check_bg_victims(sbi);
@@ -395,6 +411,8 @@ next:
 	}
 	if (p.min_segno != NULL_SEGNO) {
 got_it:
+		*result = (p.min_segno / p.ofs_unit) * p.ofs_unit;
+got_result:
 		if (p.alloc_mode == LFS) {
 			secno = GET_SEC_FROM_SEG(sbi, p.min_segno);
 			if (gc_type == FG_GC)
@@ -402,7 +420,6 @@ got_it:
 			else
 				set_bit(secno, dirty_i->victim_secmap);
 		}
-		*result = (p.min_segno / p.ofs_unit) * p.ofs_unit;
 
 		trace_f2fs_get_victim(sbi->sb, type, gc_type, &p,
 				sbi->cur_victim_sec,
@@ -1103,15 +1120,18 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 	struct blk_plug plug;
 	unsigned int segno = start_segno;
 	unsigned int end_segno = start_segno + sbi->segs_per_sec;
-	int seg_freed = 0;
+	int seg_freed = 0, migrated = 0;
 	unsigned char type = IS_DATASEG(get_seg_entry(sbi, segno)->type) ?
 						SUM_TYPE_DATA : SUM_TYPE_NODE;
 	int submitted = 0;
 
+	if (__is_large_section(sbi))
+		end_segno = rounddown(end_segno, sbi->segs_per_sec);
+
 	/* readahead multi ssa blocks those have contiguous address */
 	if (__is_large_section(sbi))
 		f2fs_ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno),
-					sbi->segs_per_sec, META_SSA, true);
+					end_segno - segno, META_SSA, true);
 
 	/* reference all summary page */
 	while (segno < end_segno) {
@@ -1142,8 +1162,11 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 
 		if (get_valid_blocks(sbi, segno, false) == 0)
 			goto freed;
+		if (__is_large_section(sbi) &&
+				migrated >= sbi->migration_granularity)
+			goto skip;
 		if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
-			goto next;
+			goto skip;
 
 		sum = page_address(sum_page);
 		if (type != GET_SUM_TYPE((&sum->footer))) {
@@ -1151,7 +1174,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 				"type [%d, %d] in SSA and SIT",
 				segno, type, GET_SUM_TYPE((&sum->footer)));
 			set_sbi_flag(sbi, SBI_NEED_FSCK);
-			goto next;
+			goto skip;
 		}
 
 		/*
@@ -1174,7 +1197,11 @@ freed:
 		if (gc_type == FG_GC &&
 				get_valid_blocks(sbi, segno, false) == 0)
 			seg_freed++;
-next:
+		migrated++;
+
+		if (__is_large_section(sbi) && segno + 1 < end_segno)
+			sbi->next_victim_seg[gc_type] = segno + 1;
+skip:
 		f2fs_put_page(sum_page, 0);
 	}