On 07/14, Yunlong Song wrote:
> Suppose that the valid blocks of each section are all over
> sbi->fggc_threshold,
> and even has_not_enough_free_secs is true, f2fs_gc cannot do its job since the
> no_fggc_candidate always returns true. As a result, the reserved segments can
> be
> used up, and finally there is no free segment at all, and get_new_segment
> cannot
> get a free segment, filesystem will trap into a wrong status.
>
> To fix this, we record the segno which has a rough minimum cost and return it
> to
> __get_victim to continue f2fs_gc's job.
>
> Signed-off-by: Yunlong Song <yunlong.s...@huawei.com>
> ---
> fs/f2fs/gc.c | 19 ++++++++++++++-----
> fs/f2fs/segment.h | 17 ++++++++++++++---
> 2 files changed, 28 insertions(+), 8 deletions(-)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index fa3d2e2..965e783 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -178,6 +178,8 @@ static void select_policy(struct f2fs_sb_info *sbi, int
> gc_type,
> p->offset = 0;
> else
> p->offset = SIT_I(sbi)->last_victim[p->gc_mode];
> +
> + p->min_cost_r = UINT_MAX;
> }
>
> static unsigned int get_max_cost(struct f2fs_sb_info *sbi,
> @@ -194,7 +196,7 @@ static unsigned int get_max_cost(struct f2fs_sb_info *sbi,
> return 0;
> }
>
> -static unsigned int check_bg_victims(struct f2fs_sb_info *sbi)
> +static unsigned int check_bg_victims(struct f2fs_sb_info *sbi, struct
> victim_sel_policy *p)
> {
> struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
> unsigned int secno;
> @@ -208,11 +210,12 @@ static unsigned int check_bg_victims(struct
> f2fs_sb_info *sbi)
> if (sec_usage_check(sbi, secno))
> continue;
>
> - if (no_fggc_candidate(sbi, secno))
> + p->cur_segno_r = GET_SEG_FROM_SEC(sbi, secno);
> + if (no_fggc_candidate(sbi, secno, p))
> continue;
>
> clear_bit(secno, dirty_i->victim_secmap);
> - return GET_SEG_FROM_SEC(sbi, secno);
> + return p->cur_segno_r;
> }
> return NULL_SEGNO;
> }
> @@ -332,7 +335,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
>
> last_victim = sm->last_victim[p.gc_mode];
> if (p.alloc_mode == LFS && gc_type == FG_GC) {
> - p.min_segno = check_bg_victims(sbi);
> + p.min_segno = check_bg_victims(sbi, &p);
> if (p.min_segno != NULL_SEGNO)
> goto got_it;
> }
> @@ -369,8 +372,9 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
> goto next;
> if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
> goto next;
> + p.cur_segno_r = segno;
> if (gc_type == FG_GC && p.alloc_mode == LFS &&
> - no_fggc_candidate(sbi, secno))
> + no_fggc_candidate(sbi, secno, &p))
> goto next;
>
> cost = get_gc_cost(sbi, segno, &p);
> @@ -403,6 +407,11 @@ static int get_victim_by_default(struct f2fs_sb_info
> *sbi,
> trace_f2fs_get_victim(sbi->sb, type, gc_type, &p,
> sbi->cur_victim_sec,
> prefree_segments(sbi), free_segments(sbi));
> + } else if (has_not_enough_free_secs(sbi, 0, 0)) {
> + p.min_segno = p.min_segno_r;
> + if (p.alloc_mode == LFS && gc_type == FG_GC)
> + clear_bit(GET_SEC_FROM_SEG(sbi, p.min_segno),
> dirty_i->victim_secmap);
It seems you want to give a victim segment which has valid blocks larger than
fggc_threshold.
fggc: 507
reserve: 462
cnt_full: 25182
over: 25912 (>= fggc)
less: 870 (< fggc)
What is ovp segments?
It looks like there are 870 candidates for FG_GC, and GC with 103 segments must
give 104 free segments in the worst case. Is there a problem on p.max_search?
Thanks,
> + goto got_it;
> }
> out:
> mutex_unlock(&dirty_i->seglist_lock);
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 6b871b4..7d2d0f3 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -169,6 +169,9 @@ struct victim_sel_policy {
> unsigned int ofs_unit; /* bitmap search unit */
> unsigned int min_cost; /* minimum cost */
> unsigned int min_segno; /* segment # having min. cost */
> + unsigned int min_cost_r; /* rough minimum cost */
> + unsigned int min_segno_r; /* segment # having rough min.
> cost */
> + unsigned int cur_segno_r; /* segment # rough process is
> handling */
> };
>
> struct seg_entry {
> @@ -743,11 +746,19 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info
> *sbi, int base, int type)
> }
>
> static inline bool no_fggc_candidate(struct f2fs_sb_info *sbi,
> - unsigned int secno)
> + unsigned int secno, struct
> victim_sel_policy *p)
> {
> - if (get_valid_blocks(sbi, GET_SEG_FROM_SEC(sbi, secno), true) >=
> - sbi->fggc_threshold)
> + unsigned int cur_cost;
> +
> + cur_cost = get_valid_blocks(sbi, GET_SEG_FROM_SEC(sbi, secno), true);
> + if (cur_cost >= sbi->fggc_threshold) {
> + if (p->min_cost_r > cur_cost) {
> + p->min_cost_r = cur_cost;
> + p->min_segno_r = p->cur_segno_r;
> + }
> return true;
> + }
> +
> return false;
> }
>
> --
> 1.8.5.2
