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Message-ID: <6f374ac6-b9a3-9d96-35c3-49ef2e45ea77@huawei.com>
Date: Mon, 24 Jul 2017 17:18:55 +0800
From: Yunlong Song <yunlong.song@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
CC: sylinux <sylinux@....com>, chao <chao@...nel.org>,
yuchao0 <yuchao0@...wei.com>, miaoxie <miaoxie@...wei.com>,
"bintian.wang" <bintian.wang@...wei.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
linux-f2fs-devel <linux-f2fs-devel@...ts.sourceforge.net>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: let __get_victim successfully get a segno in corner
case
Hi Jay,
fggc_threshold is 507, reserved_segment is 462.
On 2017/7/22 5:07, Jaegeuk Kim wrote:
> Hi Yunlong,
>
> On 07/20, Yunlong Song wrote:
>> Hi, Jay,
>> The distribution is like this, unit is segment counts:
>> cnt_free: 0 (free blocks)
>> cnt_full: 25182 (segment which has 512 blocks)
>> cnt_over: 25192 (segment which valid blocks over fggc_threshold)
>> cnt_below: 870 (segment which valid blocks below fggc_threshold)
> What are the values of fggc_threshold and ovp ratio or reserved_segments?
> How was the proc/segment_info?
>
> Thanks,
>
>> The test is fragment test, add and delete small files over and over.
>>
>> On 2017/7/18 0:56, Jaegeuk Kim wrote:
>>> On 07/16, sylinux wrote:
>>>> In fact，this is not "suppose" case yet, we have already met this problem several times in some test suits for corner case, or I cannot notice that this could happen.
>>> So, have you taken a look at distribution of valid blocks in that case?
>>> I'm wondering what distribution can cause this.
>>>
>>> Thanks,
>>>
>>>>
>>>>
>>>> 发自网易邮箱大师
>>>> On 07/16/2017 09:09, Jaegeuk Kim wrote:
>>>> Hi Yunlong,
>>>>
>>>> On 07/14, Yunlong Song wrote:
>>>>> Suppose that the valid blocks of each section are all over sbi->fggc_threshold,
>>>> How about adding a kernel message first to detect your *supposed* sceanrio?
>>>> If that happens, it'll be a sort of bug which we haven't assumed.
>>>>
>>>> Thanks,
>>>>
>>>>> 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@...wei.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);
>>>>> + 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
>>
> .
>
--
Thanks,
Yunlong Song
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