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

[Daeho Jeong]

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?

2021년 2월 2일 (화) 오후 6:55, Chao Yu <yuchao0@xxxxxxxxxx>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@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,
> >>>
> > .
> >