Re: [PATCH v3 2/2] mm/damon/dbgfs: Add adaptive_targets list check before enable monitor_on

From: SeongJae Park <sj@kernel.org>
To: SeongJae Park <sj@kernel.org>
Cc: Xin Hao <xhao@linux.alibaba.com>,
	sjpark@amazon.de, akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/2] mm/damon/dbgfs: Add adaptive_targets list check before enable monitor_on
Date: Wed, 20 Oct 2021 08:12:33 +0000	[thread overview]
Message-ID: <20211020081233.28363-1-sj@kernel.org> (raw)
In-Reply-To: <20211020072121.17166-1-sj@kernel.org>

On Wed, 20 Oct 2021 07:21:21 +0000 SeongJae Park <sj@kernel.org> wrote:

> On Wed, 20 Oct 2021 09:42:33 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:
> 
> > When the ctx->adaptive_targets list is empty,
> > I did some test on monitor_on interface like this.
> > 
> >     # echo > /sys/kernel/debug/damon/target_ids
> 
> Thanks for the change, but you missed writing 'on' to 'monitor_on' in the above
> example.
> 
> > 
> > Though the ctx->adaptive_targets list is empty, but the
> > kthread_run still be called, and the kdamond.x thread still
> > be created, this is meaningless.
> > 
> > So there adds a judgment in 'dbgfs_monitor_on_write',
> > if the ctx->adaptive_targets list is empty, return -EINVAL.
> > 
> > Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
> 
> Other parts looks good to me.  However, seems this commit conflicts with a
> patch[1] which already merged in -mm tree.  Could you please rebase this on it?
> FYI, all DAMON patches that merged in -mm tree are also applied on DAMON
> development tree.  So, you could get the patch applied tree by:
> 
>     $ git remote add sj git://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git
>     $ git fetch sj
>     $ git checkout 0fa378d04b12
> 
> [1] https://lore.kernel.org/linux-mm/20211014073014.35754-1-sj@kernel.org/
> 
> 
> Thanks,
> SJ
> 
> > ---
> >  include/linux/damon.h |  1 +
> >  mm/damon/core.c       |  5 +++++
> >  mm/damon/dbgfs.c      | 13 ++++++++++---
> >  3 files changed, 16 insertions(+), 3 deletions(-)
> > 
> > diff --git a/include/linux/damon.h b/include/linux/damon.h
> > index 715dadd21f7c..4fce5f1f6dad 100644
> > --- a/include/linux/damon.h
> > +++ b/include/linux/damon.h
> > @@ -316,6 +316,7 @@ void damon_destroy_scheme(struct damos *s);
> > 
> >  struct damon_target *damon_new_target(unsigned long id);
> >  void damon_add_target(struct damon_ctx *ctx, struct damon_target *t);
> > +bool damon_targets_empty(struct damon_ctx *ctx);
> >  void damon_free_target(struct damon_target *t);
> >  void damon_destroy_target(struct damon_target *t);
> >  unsigned int damon_nr_regions(struct damon_target *t);
> > diff --git a/mm/damon/core.c b/mm/damon/core.c
> > index 2f6785737902..c3a1374dbe0b 100644
> > --- a/mm/damon/core.c
> > +++ b/mm/damon/core.c
> > @@ -156,6 +156,11 @@ void damon_add_target(struct damon_ctx *ctx, struct damon_target *t)
> >  	list_add_tail(&t->list, &ctx->adaptive_targets);
> >  }
> > 
> > +bool damon_targets_empty(struct damon_ctx *ctx)
> > +{
> > +	return list_empty(&ctx->adaptive_targets);
> > +}
> > +
> >  static void damon_del_target(struct damon_target *t)
> >  {
> >  	list_del(&t->list);
> > diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
> > index 38188347d8ab..9dee29f7d103 100644
> > --- a/mm/damon/dbgfs.c
> > +++ b/mm/damon/dbgfs.c
> > @@ -865,12 +865,19 @@ static ssize_t dbgfs_monitor_on_write(struct file *file,
> >  		return -EINVAL;
> >  	}
> > 
> > -	if (!strncmp(kbuf, "on", count))
> > +	if (!strncmp(kbuf, "on", count)) {
> > +		int i;
> > +
> > +		for (i = 0; i < dbgfs_nr_ctxs; i++) {
> > +			if (damon_targets_empty(dbgfs_ctxs[i]))
> > +				return -EINVAL;

Oops, I forgot that you should 'kfree(kbuf)' before returning here.  Please do
that.

Thanks,
SJ

> > +		}
> >  		err = damon_start(dbgfs_ctxs, dbgfs_nr_ctxs);
> > -	else if (!strncmp(kbuf, "off", count))
> > +	} else if (!strncmp(kbuf, "off", count)) {
> >  		err = damon_stop(dbgfs_ctxs, dbgfs_nr_ctxs);
> > -	else
> > +	} else {
> >  		err = -EINVAL;
> > +	}
> > 
> >  	if (err)
> >  		ret = err;
> > --
> > 2.31.0
> 
> 