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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>
References: <20210302054233.3886681-1-jaegeuk@kernel.org>
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 <05b43d3e-d735-ae34-5a4f-3d81a4fc8a9b@huawei.com>
 <YEEd1q5nz9EYGy8H@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <ee90aac8-bc84-0a85-e1b8-f51c40c77535@huawei.com>
Date:   Fri, 5 Mar 2021 10:19:31 +0800
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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.

> 
>>
>>>
>>> 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.

/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
>>> .
>>>
> .
>