f2fs: remain last victim segment number ascending order

This patch avoids to remain inefficient victim segment number selected by
a victim.

For example, if all the dirty segments has same valid blocks, we can get
the victim segments descending order due to keeping wrong last segment number.

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

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 47ade35..c013534 100644 (file)
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -270,7 +270,7 @@ 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 secno, max_cost;
+       unsigned int secno, max_cost, last_victim;
        unsigned int last_segment = MAIN_SEGS(sbi);
        unsigned int nsearched = 0;
 
@@ -285,6 +285,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
        if (p.max_search == 0)
                goto out;
 
+       last_victim = sbi->last_victim[p.gc_mode];
        if (p.alloc_mode == LFS && gc_type == FG_GC) {
                p.min_segno = check_bg_victims(sbi);
                if (p.min_segno != NULL_SEGNO)
@@ -332,7 +333,10 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
                }
 next:
                if (nsearched >= p.max_search) {
-                       sbi->last_victim[p.gc_mode] = segno;
+                       if (!sbi->last_victim[p.gc_mode] && segno <= last_victim)
+                               sbi->last_victim[p.gc_mode] = last_victim + 1;
+                       else
+                               sbi->last_victim[p.gc_mode] = segno + 1;
                        break;
                }
        }