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Subject: Re: [f2fs-dev] [PATCH] f2fs: expose # of overprivision segments
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <kernel-team@android.com>, <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>
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From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <37c84a6f-f42b-469e-5897-06da71887ba1@huawei.com>
Date:   Tue, 9 Mar 2021 10:50:49 +0800
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On 2021/3/9 8:07, Jaegeuk Kim wrote:
> On 03/05, Chao Yu wrote:
>> On 2021/3/5 1:50, Jaegeuk Kim wrote:
>>> On 03/04, Chao Yu wrote:
>>>> On 2021/3/3 2:44, Jaegeuk Kim wrote:
>>>>> On 03/02, Jaegeuk Kim wrote:
>>>>>> On 03/02, Chao Yu wrote:
>>>>>>> On 2021/3/2 13:42, Jaegeuk Kim wrote:
>>>>>>>> This is useful when checking conditions during checkpoint=disable in Android.
>>>>>>>
>>>>>>> This sysfs entry is readonly, how about putting this at
>>>>>>> /sys/fs/f2fs/<disk>/stat/?
>>>>>>
>>>>>> Urg.. "stat" is a bit confused. I'll take a look a better ones.
>>>>
>>>> Oh, I mean put it into "stat" directory, not "stat" entry, something like this:
>>>>
>>>> /sys/fs/f2fs/<disk>/stat/ovp_segments
>>>
>>> I meant that too. Why is it like stat, since it's a geomerty?
>>
>> Hmm.. I feel a little bit weired to treat ovp_segments as 'stat' class, one reason
>> is ovp_segments is readonly and is matching the readonly attribute of a stat.
> 
> It seems I don't fully understand what you suggest here. I don't want to add the
> # of ovp_segments in <disk>/stat, since it is not part of status, but put it in
> <disk>/ to sync with other # of free/dirty segments. If you can't read out easily,
> I suggest to create symlinks to organize all the current mess.

Alright.

> 
>>
>>>
>>>>
>>>>>
>>>>> Taking a look at other entries using in Android, I feel that this one can't be
>>>>> in stat or whatever other location, since I worry about the consistency with
>>>>> similar dirty/free segments. It seems it's not easy to clean up the existing
>>>>> ones anymore.
>>>>
>>>> Well, actually, the entry number are still increasing continuously, the result is
>>>> that it becomes more and more slower and harder for me to find target entry name
>>>> from that directory.
>>>>
>>>> IMO, once new readonly entry was added to "<disk>" directory, there is no chance
>>>> to reloacate it due to interface compatibility. So I think this is the only
>>>> chance to put it to the appropriate place at this time.
>>>
>>> I know, but this will diverge those info into different places. I don't have
>>> big concern when finding a specific entry with this tho, how about making
>>> symlinks to create a dir structure for your easy access? Or, using a script
>>> would be alternative way.
>>
>> Yes, there should be some alternative ways to help to access f2fs sysfs
>> interface, but from a point view of user, I'm not sure he can figure out those
>> ways.
>>
>> For those fs meta stat, why not adding a single entry to include all info you
>> need rather than adding them one by one? e.g.
> 
> You can add that in /proc as well, which requires to parse back when retrieving
> specific values.

Copied.

Thanks,

> 
>>
>> /proc/fs/f2fs/<disk>/super_block
>> /proc/fs/f2fs/<disk>/checkpoint
>> /proc/fs/f2fs/<disk>/nat_table
>> /proc/fs/f2fs/<disk>/sit_table
>> ...
>>
>> Thanks,
>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>>>>>>> ---
>>>>>>>>      fs/f2fs/sysfs.c | 8 ++++++++
>>>>>>>>      1 file changed, 8 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>>>>>>> index e38a7f6921dd..254b6fa17406 100644
>>>>>>>> --- a/fs/f2fs/sysfs.c
>>>>>>>> +++ b/fs/f2fs/sysfs.c
>>>>>>>> @@ -91,6 +91,13 @@ static ssize_t free_segments_show(struct f2fs_attr *a,
>>>>>>>>      			(unsigned long long)(free_segments(sbi)));
>>>>>>>>      }
>>>>>>>> +static ssize_t ovp_segments_show(struct f2fs_attr *a,
>>>>>>>> +		struct f2fs_sb_info *sbi, char *buf)
>>>>>>>> +{
>>>>>>>> +	return sprintf(buf, "%llu\n",
>>>>>>>> +			(unsigned long long)(overprovision_segments(sbi)));
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>      static ssize_t lifetime_write_kbytes_show(struct f2fs_attr *a,
>>>>>>>>      		struct f2fs_sb_info *sbi, char *buf)
>>>>>>>>      {
>>>>>>>> @@ -629,6 +636,7 @@ F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, node_io_flag, node_io_flag);
>>>>>>>>      F2FS_RW_ATTR(CPRC_INFO, ckpt_req_control, ckpt_thread_ioprio, ckpt_thread_ioprio);
>>>>>>>>      F2FS_GENERAL_RO_ATTR(dirty_segments);
>>>>>>>>      F2FS_GENERAL_RO_ATTR(free_segments);
>>>>>>>> +F2FS_GENERAL_RO_ATTR(ovp_segments);
>>>>>>>
>>>>>>> Missed to add document entry in Documentation/ABI/testing/sysfs-fs-f2fs?
>>>>>>
>>>>>> Yeah, thanks.
>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>>>      F2FS_GENERAL_RO_ATTR(lifetime_write_kbytes);
>>>>>>>>      F2FS_GENERAL_RO_ATTR(features);
>>>>>>>>      F2FS_GENERAL_RO_ATTR(current_reserved_blocks);
>>>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Linux-f2fs-devel mailing list
>>>>>> Linux-f2fs-devel@lists.sourceforge.net
>>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>>> .
>>>>>
>>> .
>>>
> .
>