Re: [f2fs-dev] [PATCH v3] f2fs: rename checkpoint=merge mount option to checkpoint_merge

[Chao Yu <chao@kernel.org>]

On 2021/2/2 19:29, Daeho Jeong wrote:
> Thanks for the explanation.
> 
> I am going to remove the line clearing "MERGE_CHECKPOINT".
> But, when we go with the below remount command, I think the
> "nocheckpoint_merge" option will work well to disable only just
> "checkpoint_merge" from the previous option.
> "mount -o remount,nocheckpoint_merge  /dir"
> 
> It would be more convenient to users. What do you think?

It's fine to me, please go ahead. :)

Thanks,

> 
> 2021년 2월 2일 (화) 오후 6:55, Chao Yu <yuchao0@huawei.com>님이 작성:
>>
>> On 2021/2/2 17:44, Daeho Jeong wrote:
>>> When we remount it without the "checkpoint_merge" option, shouldn't we
>>> need to clear "MERGE_CHECKPOINT" again?
>>> This is actually what I intended, but I was wrong. Actually, I found this.
>>>
>>> When we remount the filesystem, the previous mount option is passed
>>> through the "data" argument in the below.
>>> f2fs_remount(struct super_block *sb, int *flags, char *data)
>>>
>>> If we don't provide the "nocheckpoint_merge" option, how can we turn
>>> off the "checkpoint_merge" option which is turned on in the previous
>>> mount?
>>
>> We can use "mount -o remount /dev/xxx /mnt" to disable checkpoint_merge,
>> since that command won't pass old mount options to remount?
>>
>> Quoted from man mount:
>>
>>                 mount -o remount,rw /dev/foo /dir
>>
>>                 After  this  call  all  old  mount options are replaced and arbitrary stuff from fstab (or mtab) is ignored, except the loop= option which is internally generated and maintained by the
>>                 mount command.
>>
>>                 mount -o remount,rw  /dir
>>
>>                 After this call mount reads fstab and merges these options with the options from the command line (-o). If no mountpoint found in fstab than remount with unspecified source is allowed.
>>
>> Thanks,
>>
>>>
>>> 2021년 2월 2일 (화) 오후 6:28, Chao Yu <yuchao0@huawei.com>님이 작성:
>>>>
>>>> On 2021/2/2 17:23, Daeho Jeong wrote:
>>>>> From: Daeho Jeong <daehojeong@google.com>
>>>>>
>>>>> As checkpoint=merge comes in, mount option setting related to checkpoint
>>>>> had been mixed up and it became hard to understand. So, I separated
>>>>> this option from "checkpoint=" and made another mount option
>>>>> "checkpoint_merge" for this.
>>>>>
>>>>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
>>>>> ---
>>>>> v2: renamed "checkpoint=merge" to "checkpoint_merge"
>>>>> v3: removed "nocheckpoint_merge" option
>>>>> ---
>>>>>     Documentation/filesystems/f2fs.rst |  6 +++---
>>>>>     fs/f2fs/super.c                    | 21 +++++++++------------
>>>>>     2 files changed, 12 insertions(+), 15 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
>>>>> index d0ead45dc706..475994ed8b15 100644
>>>>> --- a/Documentation/filesystems/f2fs.rst
>>>>> +++ b/Documentation/filesystems/f2fs.rst
>>>>> @@ -247,9 +247,9 @@ checkpoint=%s[:%u[%]]      Set to "disable" to turn off checkpointing. Set to "enabl
>>>>>                          hide up to all remaining free space. The actual space that
>>>>>                          would be unusable can be viewed at /sys/fs/f2fs/<disk>/unusable
>>>>>                          This space is reclaimed once checkpoint=enable.
>>>>> -                      Here is another option "merge", which creates a kernel daemon
>>>>> -                      and makes it to merge concurrent checkpoint requests as much
>>>>> -                      as possible to eliminate redundant checkpoint issues. Plus,
>>>>> +checkpoint_merge      When checkpoint is enabled, this can be used to create a kernel
>>>>> +                      daemon and make it to merge concurrent checkpoint requests as
>>>>> +                      much as possible to eliminate redundant checkpoint issues. Plus,
>>>>>                          we can eliminate the sluggish issue caused by slow checkpoint
>>>>>                          operation when the checkpoint is done in a process context in
>>>>>                          a cgroup having low i/o budget and cpu shares. To make this
>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>> index 56696f6cfa86..b60dcef7f9d0 100644
>>>>> --- a/fs/f2fs/super.c
>>>>> +++ b/fs/f2fs/super.c
>>>>> @@ -215,7 +215,7 @@ static match_table_t f2fs_tokens = {
>>>>>         {Opt_checkpoint_disable_cap, "checkpoint=disable:%u"},
>>>>>         {Opt_checkpoint_disable_cap_perc, "checkpoint=disable:%u%%"},
>>>>>         {Opt_checkpoint_enable, "checkpoint=enable"},
>>>>> -     {Opt_checkpoint_merge, "checkpoint=merge"},
>>>>> +     {Opt_checkpoint_merge, "checkpoint_merge"},
>>>>>         {Opt_compress_algorithm, "compress_algorithm=%s"},
>>>>>         {Opt_compress_log_size, "compress_log_size=%u"},
>>>>>         {Opt_compress_extension, "compress_extension=%s"},
>>>>> @@ -1142,12 +1142,6 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>>>>>                 return -EINVAL;
>>>>>         }
>>>>>
>>>>> -     if (test_opt(sbi, DISABLE_CHECKPOINT) &&
>>>>> -                     test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>> -             f2fs_err(sbi, "checkpoint=merge cannot be used with checkpoint=disable\n");
>>>>> -             return -EINVAL;
>>>>> -     }
>>>>> -
>>>>>         /* Not pass down write hints if the number of active logs is lesser
>>>>>          * than NR_CURSEG_PERSIST_TYPE.
>>>>>          */
>>>>> @@ -1782,7 +1776,7 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
>>>>>                 seq_printf(seq, ",checkpoint=disable:%u",
>>>>>                                 F2FS_OPTION(sbi).unusable_cap);
>>>>>         if (test_opt(sbi, MERGE_CHECKPOINT))
>>>>> -             seq_puts(seq, ",checkpoint=merge");
>>>>> +             seq_puts(seq, ",checkpoint_merge");
>>>>>         if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_POSIX)
>>>>>                 seq_printf(seq, ",fsync_mode=%s", "posix");
>>>>>         else if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT)
>>>>> @@ -1827,6 +1821,7 @@ static void default_options(struct f2fs_sb_info *sbi)
>>>>>         sbi->sb->s_flags |= SB_LAZYTIME;
>>>>>         set_opt(sbi, FLUSH_MERGE);
>>>>>         set_opt(sbi, DISCARD);
>>>>> +     clear_opt(sbi, MERGE_CHECKPOINT);
>>>>
>>>> It's not needed here?
>>>>
>>>> Thanks,
>>>>
>>>>>         if (f2fs_sb_has_blkzoned(sbi))
>>>>>                 F2FS_OPTION(sbi).fs_mode = FS_MODE_LFS;
>>>>>         else
>>>>> @@ -2066,9 +2061,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>>>>>                 }
>>>>>         }
>>>>>
>>>>> -     if (!test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>> -             f2fs_stop_ckpt_thread(sbi);
>>>>> -     } else {
>>>>> +     if (!test_opt(sbi, DISABLE_CHECKPOINT) &&
>>>>> +                     test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>>                 err = f2fs_start_ckpt_thread(sbi);
>>>>>                 if (err) {
>>>>>                         f2fs_err(sbi,
>>>>> @@ -2076,6 +2070,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>>>>>                             err);
>>>>>                         goto restore_gc;
>>>>>                 }
>>>>> +     } else {
>>>>> +             f2fs_stop_ckpt_thread(sbi);
>>>>>         }
>>>>>
>>>>>         /*
>>>>> @@ -3831,7 +3827,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>>
>>>>>         /* setup checkpoint request control and start checkpoint issue thread */
>>>>>         f2fs_init_ckpt_req_control(sbi);
>>>>> -     if (test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>> +     if (!test_opt(sbi, DISABLE_CHECKPOINT) &&
>>>>> +                     test_opt(sbi, MERGE_CHECKPOINT)) {
>>>>>                 err = f2fs_start_ckpt_thread(sbi);
>>>>>                 if (err) {
>>>>>                         f2fs_err(sbi,
>>>>>
>>> .
>>>
> 
> 
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