[f2fs-dev] [PATCH v1 0/2] f2fs: modify the calculation method of mtime

[f2fs-dev] [PATCH v1 0/2] f2fs: modify the calculation method of mtime

[liuderong--- via Linux-f2fs-devel]

From: liuderong <liuderong@oppo.com>

In cost-benefit GC algorithm, mtime will affect
the selection of victim segment.For a large section,
mtime should be the mean value of valid segments,
in order to select correct victim segment,
it needs to modify the calculation method of mtime.

liuderong (2):
  f2fs: remove unused parameters
  f2fs: introduce get_section_mtime

 fs/f2fs/f2fs.h    |  5 +++--
 fs/f2fs/gc.c      | 21 +++++----------------
 fs/f2fs/segment.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
 fs/f2fs/segment.h |  4 ++--
 4 files changed, 55 insertions(+), 27 deletions(-)

--
2.7.4

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[f2fs-dev] [PATCH v1 1/2] f2fs: remove unused parameters

[liuderong--- via Linux-f2fs-devel]

From: liuderong <liuderong@oppo.com>

Remove unused parameter segno from f2fs_usable_segs_in_sec.

Signed-off-by: liuderong <liuderong@oppo.com>
---
 fs/f2fs/f2fs.h    | 3 +--
 fs/f2fs/gc.c      | 6 +++---
 fs/f2fs/segment.c | 3 +--
 fs/f2fs/segment.h | 4 ++--
 4 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ac19c61..4dcdcdd 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3759,8 +3759,7 @@ void f2fs_destroy_segment_manager_caches(void);
 int f2fs_rw_hint_to_seg_type(struct f2fs_sb_info *sbi, enum rw_hint hint);
 enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info *sbi,
                        enum page_type type, enum temp_type temp);
-unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi,
-                       unsigned int segno);
+unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi);
 unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
                        unsigned int segno);

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 724bbcb..6299639 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -339,7 +339,7 @@ static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno)
        unsigned char age = 0;
        unsigned char u;
        unsigned int i;
-       unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi, segno);
+       unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);

        for (i = 0; i < usable_segs_per_sec; i++)
                mtime += get_seg_entry(sbi, start + i)->mtime;
@@ -1707,7 +1707,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
         */
        if (f2fs_sb_has_blkzoned(sbi))
                end_segno -= SEGS_PER_SEC(sbi) -
-                                       f2fs_usable_segs_in_sec(sbi, segno);
+                                       f2fs_usable_segs_in_sec(sbi);

        sanity_check_seg_type(sbi, get_seg_entry(sbi, segno)->type);

@@ -1881,7 +1881,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)

        total_freed += seg_freed;

-       if (seg_freed == f2fs_usable_segs_in_sec(sbi, segno)) {
+       if (seg_freed == f2fs_usable_segs_in_sec(sbi)) {
                sec_freed++;
                total_sec_freed++;
        }
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 78c3198..6627394 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -5381,8 +5381,7 @@ unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
        return BLKS_PER_SEG(sbi);
 }

-unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi,
-                                       unsigned int segno)
+unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi)
 {
        if (f2fs_sb_has_blkzoned(sbi))
                return CAP_SEGS_PER_SEC(sbi);
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index bfc01a5..9e61ded 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -430,7 +430,7 @@ static inline void __set_free(struct f2fs_sb_info *sbi, unsigned int segno)
        unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
        unsigned int start_segno = GET_SEG_FROM_SEC(sbi, secno);
        unsigned int next;
-       unsigned int usable_segs = f2fs_usable_segs_in_sec(sbi, segno);
+       unsigned int usable_segs = f2fs_usable_segs_in_sec(sbi);

        spin_lock(&free_i->segmap_lock);
        clear_bit(segno, free_i->free_segmap);
@@ -464,7 +464,7 @@ static inline void __set_test_and_free(struct f2fs_sb_info *sbi,
        unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
        unsigned int start_segno = GET_SEG_FROM_SEC(sbi, secno);
        unsigned int next;
-       unsigned int usable_segs = f2fs_usable_segs_in_sec(sbi, segno);
+       unsigned int usable_segs = f2fs_usable_segs_in_sec(sbi);

        spin_lock(&free_i->segmap_lock);
        if (test_and_clear_bit(segno, free_i->free_segmap)) {
--
2.7.4

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[f2fs-dev] [PATCH v1 2/2] f2fs: introduce get_section_mtime

[liuderong--- via Linux-f2fs-devel]

From: liuderong <liuderong@oppo.com>

When segs_per_sec is larger than 1, section may contain free segments,
mtime should be the mean value of each valid segments,
so introduce get_section_mtime to exclude free segments in a section.

Signed-off-by: liuderong <liuderong@oppo.com>
---
 fs/f2fs/f2fs.h    |  2 ++
 fs/f2fs/gc.c      | 15 ++-------------
 fs/f2fs/segment.c | 49 ++++++++++++++++++++++++++++++++++++++++++++-----
 3 files changed, 48 insertions(+), 18 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4dcdcdd..d6adf0f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3762,6 +3762,8 @@ enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info *sbi,
 unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi);
 unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
                        unsigned int segno);
+unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
+                       unsigned int segno);

 #define DEF_FRAGMENT_SIZE      4
 #define MIN_FRAGMENT_SIZE      1
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 6299639..03c6117 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -332,20 +332,14 @@ static unsigned int check_bg_victims(struct f2fs_sb_info *sbi)
 static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno)
 {
        struct sit_info *sit_i = SIT_I(sbi);
-       unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
-       unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
        unsigned long long mtime = 0;
        unsigned int vblocks;
        unsigned char age = 0;
        unsigned char u;
-       unsigned int i;
        unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);

-       for (i = 0; i < usable_segs_per_sec; i++)
-               mtime += get_seg_entry(sbi, start + i)->mtime;
+       mtime = get_section_mtime(sbi, segno);
        vblocks = get_valid_blocks(sbi, segno, true);
-
-       mtime = div_u64(mtime, usable_segs_per_sec);
        vblocks = div_u64(vblocks, usable_segs_per_sec);

        u = BLKS_TO_SEGS(sbi, vblocks * 100);
@@ -485,10 +479,7 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
                                struct victim_sel_policy *p, unsigned int segno)
 {
        struct sit_info *sit_i = SIT_I(sbi);
-       unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
-       unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
        unsigned long long mtime = 0;
-       unsigned int i;

        if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
                if (p->gc_mode == GC_AT &&
@@ -496,9 +487,7 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
                        return;
        }

-       for (i = 0; i < SEGS_PER_SEC(sbi); i++)
-               mtime += get_seg_entry(sbi, start + i)->mtime;
-       mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
+       mtime = get_section_mtime(sbi, segno);

        /* Handle if the system time has changed by the user */
        if (mtime < sit_i->min_mtime)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 6627394..b63f35fa 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -5389,6 +5389,49 @@ unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi)
        return SEGS_PER_SEC(sbi);
 }

+unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
+       unsigned int segno)
+{
+       unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);
+       unsigned int secno = 0, start = 0;
+       struct free_segmap_info *free_i = FREE_I(sbi);
+       unsigned int valid_seg_count = 0;
+       unsigned long long mtime = 0;
+       unsigned int i;
+
+       if (segno == NULL_SEGNO)
+               return 0;
+
+       secno = GET_SEC_FROM_SEG(sbi, segno);
+       start = GET_SEG_FROM_SEC(sbi, secno);
+
+       for (i = 0; i < usable_segs_per_sec; i++) {
+               /* for large section, only check the mtime of valid segments */
+               if (__is_large_section(sbi)) {
+                       spin_lock(&free_i->segmap_lock);
+                       if (test_bit(start + i, free_i->free_segmap)) {
+                               mtime += get_seg_entry(sbi, start + i)->mtime;
+                               valid_seg_count++;
+                       }
+                       spin_unlock(&free_i->segmap_lock);
+               } else {
+                       mtime += get_seg_entry(sbi, start + i)->mtime;
+               }
+       }
+
+       if (__is_large_section(sbi)) {
+               if (!valid_seg_count)
+                       goto out;
+               mtime = div_u64(mtime, valid_seg_count);
+       } else {
+               mtime = div_u64(mtime, usable_segs_per_sec);
+       }
+
+out:
+       return mtime;
+}
+
 /*
  * Update min, max modified time for cost-benefit GC algorithm
  */
@@ -5402,13 +5445,9 @@ static void init_min_max_mtime(struct f2fs_sb_info *sbi)
        sit_i->min_mtime = ULLONG_MAX;

        for (segno = 0; segno < MAIN_SEGS(sbi); segno += SEGS_PER_SEC(sbi)) {
-               unsigned int i;
                unsigned long long mtime = 0;

-               for (i = 0; i < SEGS_PER_SEC(sbi); i++)
-                       mtime += get_seg_entry(sbi, segno + i)->mtime;
-
-               mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
+               mtime = get_section_mtime(sbi, segno);

                if (sit_i->min_mtime > mtime)
                        sit_i->min_mtime = mtime;
--
2.7.4

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Re: [f2fs-dev] [PATCH v1 1/2] f2fs: remove unused parameters

[Chao Yu via Linux-f2fs-devel]

On 2024/9/11 10:40, liuderong@oppo.com wrote:
> From: liuderong <liuderong@oppo.com>
> 
> Remove unused parameter segno from f2fs_usable_segs_in_sec.
> 
> Signed-off-by: liuderong <liuderong@oppo.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,


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Re: [f2fs-dev] [PATCH v1 2/2] f2fs: introduce get_section_mtime

[Chao Yu via Linux-f2fs-devel]

On 2024/9/11 10:40, liuderong@oppo.com wrote:
> From: liuderong <liuderong@oppo.com>
> 
> When segs_per_sec is larger than 1, section may contain free segments,
> mtime should be the mean value of each valid segments,
> so introduce get_section_mtime to exclude free segments in a section.
> 
> Signed-off-by: liuderong <liuderong@oppo.com>
> ---
>   fs/f2fs/f2fs.h    |  2 ++
>   fs/f2fs/gc.c      | 15 ++-------------
>   fs/f2fs/segment.c | 49 ++++++++++++++++++++++++++++++++++++++++++++-----
>   3 files changed, 48 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 4dcdcdd..d6adf0f 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3762,6 +3762,8 @@ enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info *sbi,
>   unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi);
>   unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
>                          unsigned int segno);
> +unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
> +                       unsigned int segno);
> 
>   #define DEF_FRAGMENT_SIZE      4
>   #define MIN_FRAGMENT_SIZE      1
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 6299639..03c6117 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -332,20 +332,14 @@ static unsigned int check_bg_victims(struct f2fs_sb_info *sbi)
>   static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno)
>   {
>          struct sit_info *sit_i = SIT_I(sbi);
> -       unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> -       unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
>          unsigned long long mtime = 0;
>          unsigned int vblocks;
>          unsigned char age = 0;
>          unsigned char u;
> -       unsigned int i;
>          unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);
> 
> -       for (i = 0; i < usable_segs_per_sec; i++)
> -               mtime += get_seg_entry(sbi, start + i)->mtime;
> +       mtime = get_section_mtime(sbi, segno);
>          vblocks = get_valid_blocks(sbi, segno, true);
> -
> -       mtime = div_u64(mtime, usable_segs_per_sec);
>          vblocks = div_u64(vblocks, usable_segs_per_sec);
> 
>          u = BLKS_TO_SEGS(sbi, vblocks * 100);
> @@ -485,10 +479,7 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
>                                  struct victim_sel_policy *p, unsigned int segno)
>   {
>          struct sit_info *sit_i = SIT_I(sbi);
> -       unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> -       unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
>          unsigned long long mtime = 0;
> -       unsigned int i;
> 
>          if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
>                  if (p->gc_mode == GC_AT &&
> @@ -496,9 +487,7 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
>                          return;
>          }
> 
> -       for (i = 0; i < SEGS_PER_SEC(sbi); i++)
> -               mtime += get_seg_entry(sbi, start + i)->mtime;
> -       mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
> +       mtime = get_section_mtime(sbi, segno);
> 
>          /* Handle if the system time has changed by the user */
>          if (mtime < sit_i->min_mtime)
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 6627394..b63f35fa 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -5389,6 +5389,49 @@ unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi)
>          return SEGS_PER_SEC(sbi);
>   }
> 
> +unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
> +       unsigned int segno)
> +{
> +       unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);
> +       unsigned int secno = 0, start = 0;
> +       struct free_segmap_info *free_i = FREE_I(sbi);
> +       unsigned int valid_seg_count = 0;
> +       unsigned long long mtime = 0;
> +       unsigned int i;
> +
> +       if (segno == NULL_SEGNO)
> +               return 0;
> +
> +       secno = GET_SEC_FROM_SEG(sbi, segno);
> +       start = GET_SEG_FROM_SEC(sbi, secno);
> +
> +       for (i = 0; i < usable_segs_per_sec; i++) {
> +               /* for large section, only check the mtime of valid segments */
> +               if (__is_large_section(sbi)) {
> +                       spin_lock(&free_i->segmap_lock);
> +                       if (test_bit(start + i, free_i->free_segmap)) {
> +                               mtime += get_seg_entry(sbi, start + i)->mtime;
> +                               valid_seg_count++;
> +                       }
> +                       spin_unlock(&free_i->segmap_lock);
> +               } else {
> +                       mtime += get_seg_entry(sbi, start + i)->mtime;
> +               }
> +       }
> +
> +       if (__is_large_section(sbi)) {
> +               if (!valid_seg_count)
> +                       goto out;
> +               mtime = div_u64(mtime, valid_seg_count);
> +       } else {
> +               mtime = div_u64(mtime, usable_segs_per_sec);
> +       }

What about:

if (!__is_large_section(sbi))
	return get_seg_entry(sbi, start + i)->mtime;

for (i = 0; i < usable_segs_per_sec; i++) {
	/* for large section, only check the mtime of valid segments */
	...
}

return div_u64(mtime, usable_segs_per_sec);

Thanks,

> +
> +out:
> +       return mtime;
> +}
> +
>   /*
>    * Update min, max modified time for cost-benefit GC algorithm
>    */
> @@ -5402,13 +5445,9 @@ static void init_min_max_mtime(struct f2fs_sb_info *sbi)
>          sit_i->min_mtime = ULLONG_MAX;
> 
>          for (segno = 0; segno < MAIN_SEGS(sbi); segno += SEGS_PER_SEC(sbi)) {
> -               unsigned int i;
>                  unsigned long long mtime = 0;
> 
> -               for (i = 0; i < SEGS_PER_SEC(sbi); i++)
> -                       mtime += get_seg_entry(sbi, segno + i)->mtime;
> -
> -               mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
> +               mtime = get_section_mtime(sbi, segno);
> 
>                  if (sit_i->min_mtime > mtime)
>                          sit_i->min_mtime = mtime;
> --
> 2.7.4



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Re: [f2fs-dev] [PATCH v1 2/2] f2fs: introduce get_section_mtime

[liuderong via Linux-f2fs-devel]

On 2024/9/11 18:22, Chao Yu wrote:
> On 2024/9/11 10:40, liuderong@oppo.com wrote:
>> From: liuderong <liuderong@oppo.com>
>>
>> When segs_per_sec is larger than 1, section may contain free segments,
>> mtime should be the mean value of each valid segments,
>> so introduce get_section_mtime to exclude free segments in a section.
>>
>> Signed-off-by: liuderong <liuderong@oppo.com>
>> ---
>>   fs/f2fs/f2fs.h    |  2 ++
>>   fs/f2fs/gc.c      | 15 ++-------------
>>   fs/f2fs/segment.c | 49 
>> ++++++++++++++++++++++++++++++++++++++++++++-----
>>   3 files changed, 48 insertions(+), 18 deletions(-)
>>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 4dcdcdd..d6adf0f 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -3762,6 +3762,8 @@ enum rw_hint f2fs_io_type_to_rw_hint(struct 
>> f2fs_sb_info *sbi,
>>   unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi);
>>   unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
>>                          unsigned int segno);
>> +unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
>> +                       unsigned int segno);
>>
>>   #define DEF_FRAGMENT_SIZE      4
>>   #define MIN_FRAGMENT_SIZE      1
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index 6299639..03c6117 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -332,20 +332,14 @@ static unsigned int check_bg_victims(struct 
>> f2fs_sb_info *sbi)
>>   static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned 
>> int segno)
>>   {
>>          struct sit_info *sit_i = SIT_I(sbi);
>> -       unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
>> -       unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
>>          unsigned long long mtime = 0;
>>          unsigned int vblocks;
>>          unsigned char age = 0;
>>          unsigned char u;
>> -       unsigned int i;
>>          unsigned int usable_segs_per_sec = 
>> f2fs_usable_segs_in_sec(sbi);
>>
>> -       for (i = 0; i < usable_segs_per_sec; i++)
>> -               mtime += get_seg_entry(sbi, start + i)->mtime;
>> +       mtime = get_section_mtime(sbi, segno);
>>          vblocks = get_valid_blocks(sbi, segno, true);
>> -
>> -       mtime = div_u64(mtime, usable_segs_per_sec);
>>          vblocks = div_u64(vblocks, usable_segs_per_sec);
>>
>>          u = BLKS_TO_SEGS(sbi, vblocks * 100);
>> @@ -485,10 +479,7 @@ static void add_victim_entry(struct f2fs_sb_info 
>> *sbi,
>>                                  struct victim_sel_policy *p, 
>> unsigned int segno)
>>   {
>>          struct sit_info *sit_i = SIT_I(sbi);
>> -       unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
>> -       unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
>>          unsigned long long mtime = 0;
>> -       unsigned int i;
>>
>>          if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
>>                  if (p->gc_mode == GC_AT &&
>> @@ -496,9 +487,7 @@ static void add_victim_entry(struct f2fs_sb_info 
>> *sbi,
>>                          return;
>>          }
>>
>> -       for (i = 0; i < SEGS_PER_SEC(sbi); i++)
>> -               mtime += get_seg_entry(sbi, start + i)->mtime;
>> -       mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
>> +       mtime = get_section_mtime(sbi, segno);
>>
>>          /* Handle if the system time has changed by the user */
>>          if (mtime < sit_i->min_mtime)
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 6627394..b63f35fa 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -5389,6 +5389,49 @@ unsigned int f2fs_usable_segs_in_sec(struct 
>> f2fs_sb_info *sbi)
>>          return SEGS_PER_SEC(sbi);
>>   }
>>
>> +unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
>> +       unsigned int segno)
>> +{
>> +       unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);
>> +       unsigned int secno = 0, start = 0;
>> +       struct free_segmap_info *free_i = FREE_I(sbi);
>> +       unsigned int valid_seg_count = 0;
>> +       unsigned long long mtime = 0;
>> +       unsigned int i;
>> +
>> +       if (segno == NULL_SEGNO)
>> +               return 0;
>> +
>> +       secno = GET_SEC_FROM_SEG(sbi, segno);
>> +       start = GET_SEG_FROM_SEC(sbi, secno);
>> +
>> +       for (i = 0; i < usable_segs_per_sec; i++) {
>> +               /* for large section, only check the mtime of valid 
>> segments */
>> +               if (__is_large_section(sbi)) {
>> +                       spin_lock(&free_i->segmap_lock);
>> +                       if (test_bit(start + i, free_i->free_segmap)) {
>> +                               mtime += get_seg_entry(sbi, start + 
>> i)->mtime;
>> +                               valid_seg_count++;
>> +                       }
>> + spin_unlock(&free_i->segmap_lock);
>> +               } else {
>> +                       mtime += get_seg_entry(sbi, start + i)->mtime;
>> +               }
>> +       }
>> +
>> +       if (__is_large_section(sbi)) {
>> +               if (!valid_seg_count)
>> +                       goto out;
>> +               mtime = div_u64(mtime, valid_seg_count);
>> +       } else {
>> +               mtime = div_u64(mtime, usable_segs_per_sec);
>> +       }
>
> What about:
>
> if (!__is_large_section(sbi))
>        return get_seg_entry(sbi, start + i)->mtime;
>
> for (i = 0; i < usable_segs_per_sec; i++) {
>        /* for large section, only check the mtime of valid segments */
>        ...
> }
>
> return div_u64(mtime, usable_segs_per_sec);
>
> Thanks,
>
OK, I will modify the code.

Thanks,

Derong

>> +
>> +out:
>> +       return mtime;
>> +}
>> +
>>   /*
>>    * Update min, max modified time for cost-benefit GC algorithm
>>    */
>> @@ -5402,13 +5445,9 @@ static void init_min_max_mtime(struct 
>> f2fs_sb_info *sbi)
>>          sit_i->min_mtime = ULLONG_MAX;
>>
>>          for (segno = 0; segno < MAIN_SEGS(sbi); segno += 
>> SEGS_PER_SEC(sbi)) {
>> -               unsigned int i;
>>                  unsigned long long mtime = 0;
>>
>> -               for (i = 0; i < SEGS_PER_SEC(sbi); i++)
>> -                       mtime += get_seg_entry(sbi, segno + i)->mtime;
>> -
>> -               mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
>> +               mtime = get_section_mtime(sbi, segno);
>>
>>                  if (sit_i->min_mtime > mtime)
>>                          sit_i->min_mtime = mtime;
>> -- 
>> 2.7.4
>


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