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

[Daeho Jeong]

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?

2021년 2월 2일 (화) 오후 6:28, Chao Yu <yuchao0@xxxxxxxxxx>님이 작성:
>
> On 2021/2/2 17:23, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > ---
> > 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,
> >