Re: [PATCH] f2fs: let __get_victim successfully get a segno in corner case
From: Yunlong Song
Date: Wed Jul 26 2017 - 22:57:12 EST
Hi, Jay,
Sorry for the mistake in last mail, the ovp is 462, and the reserved is 235.
I check the code and have not found problems with p.max_search yet.
Just forget the this patch, since there is still 870 segments below, so
it should
not be the assumed case of this patch.
By the way, I have sent another patch to provide f2fs_balance_fs to
__write_node_page,
similar as that in __write_data_page, to avoid missing f2fs_balance_fs
in node page writeback.
Please check that.
On 2017/7/26 2:55, Jaegeuk Kim wrote:
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.song@xxxxxxxxxx>
---
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
.
--
Thanks,
Yunlong Song