linux-kernel - [PATCH v3] f2fs: fix to correct freed section number during gc

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Message-id: <006e01d0f9d2$126cc130$37464390$@samsung.com>
Date:	Mon, 28 Sep 2015 17:42:24 +0800
From:	Chao Yu <chao2.yu@...sung.com>
To:	Jaegeuk Kim <jaegeuk@...nel.org>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3] f2fs: fix to correct freed section number during gc

This patch fixes to maintain the right section count freed in garbage
collecting when triggering a foreground gc.

Besides, when a foreground gc is running on current selected section, once
we fail to gc one segment, it's better to abandon gcing the left segments
in current section, because anyway we will select next victim for
foreground gc, so gc on the left segments in previous section will become
overhead and also cause the long latency for caller.

Signed-off-by: Chao Yu <chao2.yu@...sung.com>
---
v2:
 o avoid calc the wrong value when freed segments across sections.
v3:
 o cleanup code suggested by Jaegeuk Kim.
 fs/f2fs/gc.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index e932740..6f435ba 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -802,7 +802,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi)
 	unsigned int segno = NULL_SEGNO;
 	unsigned int i;
 	int gc_type = BG_GC;
-	int nfree = 0;
+	int sec_freed = 0;
 	int ret = -1;
 	struct cp_control cpc;
 	struct gc_inode_list gc_list = {
@@ -817,7 +817,7 @@ gc_more:
 	if (unlikely(f2fs_cp_error(sbi)))
 		goto stop;
 
-	if (gc_type == BG_GC && has_not_enough_free_secs(sbi, nfree)) {
+	if (gc_type == BG_GC && has_not_enough_free_secs(sbi, sec_freed)) {
 		gc_type = FG_GC;
 		if (__get_victim(sbi, &segno, gc_type) || prefree_segments(sbi))
 			write_checkpoint(sbi, &cpc);
@@ -833,13 +833,23 @@ gc_more:
 		ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno), sbi->segs_per_sec,
 								META_SSA);
 
-	for (i = 0; i < sbi->segs_per_sec; i++)
-		nfree += do_garbage_collect(sbi, segno + i, &gc_list, gc_type);
+	for (i = 0; i < sbi->segs_per_sec; i++) {
+		/*
+		 * for FG_GC case, halt gcing left segments once failed one
+		 * of segments in selected section to avoid long latency.
+		 */
+		if (!do_garbage_collect(sbi, segno + i, &gc_list, gc_type) &&
+				gc_type == FG_GC)
+			break;
+	}
+
+	if (i == sbi->segs_per_sec && gc_type == FG_GC)
+		sec_freed++;
 
 	if (gc_type == FG_GC)
 		sbi->cur_victim_sec = NULL_SEGNO;
 
-	if (has_not_enough_free_secs(sbi, nfree))
+	if (has_not_enough_free_secs(sbi, sec_freed))
 		goto gc_more;
 
 	if (gc_type == FG_GC)
-- 
2.5.2


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