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From:   =?UTF-8?B?6Zm25Yas5Yas?= <tdd21151186@gmail.com>
Date:   Thu, 5 Nov 2020 22:35:55 +0800
Message-ID: <CAJ6dUx6O2a4YJvzQ052h9eZWAOSPSSofe6O2GN6kw-ACPmkrHQ@mail.gmail.com>
Subject: Re: [PATCH] bcache: make writeback_cutoff and writeback_cutoff_sync writeable
To:     Coly Li <colyli@suse.de>
Cc:     dongdong tao <dongdong.tao@canonical.com>,
        Kent Overstreet <kent.overstreet@gmail.com>,
        "open list:BCACHE (BLOCK LAYER CACHE)" <linux-bcache@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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Ah, I missed the second part, only saw the first paragraph.
But I kind of hope it can be configurable :)
Anyway, thanks for the clarification.

Coly Li <colyli@suse.de> =E4=BA=8E2020=E5=B9=B411=E6=9C=885=E6=97=A5=E5=91=
=A8=E5=9B=9B =E4=B8=8B=E5=8D=8810:23=E5=86=99=E9=81=93=EF=BC=9A
>
> On 2020/11/5 22:19, Dongdong Tao wrote:
> > From: dongdong tao <dongdong.tao@canonical.com>
> >
> > commit 9aaf51654672 ("bcache: make cutoff_writeback and
> > cutoff_writeback_sync tunable") intend to make these two option
> > configurable by user, but these two are still read-only.
> >
> > Signed-off-by: dongdong tao <dongdong.tao@canonical.com>
> > ---
> >  drivers/md/bcache/sysfs.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
> > index 554e3afc9b68..81f4a681705c 100644
> > --- a/drivers/md/bcache/sysfs.c
> > +++ b/drivers/md/bcache/sysfs.c
> > @@ -102,8 +102,8 @@ read_attribute(writeback_keys_done);
> >  read_attribute(writeback_keys_failed);
> >  read_attribute(io_errors);
> >  read_attribute(congested);
> > -read_attribute(cutoff_writeback);
> > -read_attribute(cutoff_writeback_sync);
> > +rw_attribute(cutoff_writeback);
> > +rw_attribute(cutoff_writeback_sync);
> >  rw_attribute(congested_read_threshold_us);
> >  rw_attribute(congested_write_threshold_us);
> >
> > @@ -902,6 +902,8 @@ STORE(__bch_cache_set)
> >       sysfs_strtoul_bool(copy_gc_enabled,     c->copy_gc_enabled);
> >       sysfs_strtoul_bool(idle_max_writeback_rate,
> >                          c->idle_max_writeback_rate_enabled);
> > +     sysfs_strtoul_clamp(cutoff_writeback, bch_cutoff_writeback, 1, 10=
0);
> > +     sysfs_strtoul_clamp(cutoff_writeback_sync, bch_cutoff_writeback_s=
ync, 1, 100);
> >
>
> NACK, we only support the default value. Commit 9aaf51654672 ("bcache:
> make cutoff_writeback and cutoff_writeback_sync tunable") clearly
> announced the purpose was for research and experiment.
>
> Coly Li