f2fs: let __get_victim successfully get a segno in corner case
diff mbox

Message ID 1500033432-57620-1-git-send-email-yunlong.song@huawei.com
State New
Headers show

Commit Message

Yunlong Song July 14, 2017, 11:57 a.m. UTC
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@huawei.com>
---
 fs/f2fs/gc.c      | 19 ++++++++++++++-----
 fs/f2fs/segment.h | 17 ++++++++++++++---
 2 files changed, 28 insertions(+), 8 deletions(-)

Comments

Jaegeuk Kim July 16, 2017, 1:09 a.m. UTC | #1
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@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);
> +		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
Yunlong Song July 17, 2017, 1:51 a.m. UTC | #2
Hi Jay,
    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.

On 2017/7/16 9:09, 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@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);
>> +		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
> .
>
Jaegeuk Kim July 17, 2017, 4:56 p.m. UTC | #3
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@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);
> > +        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
Yunlong Song July 20, 2017, 12:27 p.m. UTC | #4
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)

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@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);
>>> +        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
> .
>
Jaegeuk Kim July 21, 2017, 9:07 p.m. UTC | #5
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@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);
> >>> +        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
>
Yunlong Song July 24, 2017, 9:18 a.m. UTC | #6
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@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);
>>>>> +        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
>>
> .
>
Jaegeuk Kim July 25, 2017, 6:55 p.m. UTC | #7
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@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
Yunlong Song July 27, 2017, 2:56 a.m. UTC | #8
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@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
> .
>

Patch
diff mbox

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;
 }