linux-kernel - Re: [PATCH next] ceph: Fix debugfs_simple

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Date:   Mon, 6 Jan 2020 16:04:36 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     Chen Wandun <chenwandun@...wei.com>
Cc:     Jeff Layton <jlayton@...nel.org>, Sage Weil <sage@...hat.com>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH next] ceph: Fix debugfs_simple_attr.cocci warnings

On Mon, Dec 23, 2019 at 3:32 PM Chen Wandun <chenwandun@...wei.com> wrote:
>
> Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE
> for debugfs files.
>
> Semantic patch information:
> Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file()
> imposes some significant overhead as compared to
> DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe().
>
> Signed-off-by: Chen Wandun <chenwandun@...wei.com>
> ---
>  fs/ceph/debugfs.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c
> index c281f32..60a0f1a 100644
> --- a/fs/ceph/debugfs.c
> +++ b/fs/ceph/debugfs.c
> @@ -243,8 +243,8 @@ static int congestion_kb_get(void *data, u64 *val)
>         return 0;
>  }
>
> -DEFINE_SIMPLE_ATTRIBUTE(congestion_kb_fops, congestion_kb_get,
> -                       congestion_kb_set, "%llu\n");
> +DEFINE_DEBUGFS_ATTRIBUTE(congestion_kb_fops, congestion_kb_get,
> +                        congestion_kb_set, "%llu\n");
>
>
>  void ceph_fs_debugfs_cleanup(struct ceph_fs_client *fsc)
> @@ -264,11 +264,11 @@ void ceph_fs_debugfs_init(struct ceph_fs_client *fsc)
>
>         dout("ceph_fs_debugfs_init\n");
>         fsc->debugfs_congestion_kb =
> -               debugfs_create_file("writeback_congestion_kb",
> -                                   0600,
> -                                   fsc->client->debugfs_dir,
> -                                   fsc,
> -                                   &congestion_kb_fops);
> +               debugfs_create_file_unsafe("writeback_congestion_kb",
> +                                          0600,
> +                                          fsc->client->debugfs_dir,
> +                                          fsc,
> +                                          &congestion_kb_fops);

Hi Chen,

debugfs_create_file_unsafe() has "unsafe" in its name for a reason.
Have you verified that this conversion is safe?

Thanks,

                Ilya