Re: [PATCH 1/2] ceph: add helpers to create/cleanup debugfs sub-directories under "ceph" directory

[Jeff Layton <jlayton@redhat.com>]

On Mon, 2021-08-23 at 10:25 +0530, Venky Shankar wrote:
> On Thu, Aug 19, 2021 at 10:46 PM Jeff Layton <jlayton@redhat.com> wrote:
> > 
> > On Thu, 2021-08-19 at 11:37 +0530, Venky Shankar wrote:
> > > Callers can use this helper to create a subdirectory under
> > > "ceph" directory in debugfs to place custom files for exporting
> > > information to userspace.
> > > 
> > > Signed-off-by: Venky Shankar <vshankar@redhat.com>
> > > ---
> > >  include/linux/ceph/debugfs.h |  3 +++
> > >  net/ceph/debugfs.c           | 27 +++++++++++++++++++++++++--
> > >  2 files changed, 28 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/include/linux/ceph/debugfs.h b/include/linux/ceph/debugfs.h
> > > index 8b3a1a7a953a..c372e6cb8aae 100644
> > > --- a/include/linux/ceph/debugfs.h
> > > +++ b/include/linux/ceph/debugfs.h
> > > @@ -10,5 +10,8 @@ extern void ceph_debugfs_cleanup(void);
> > >  extern void ceph_debugfs_client_init(struct ceph_client *client);
> > >  extern void ceph_debugfs_client_cleanup(struct ceph_client *client);
> > > 
> > > +extern struct dentry *ceph_debugfs_create_subdir(const char *subdir);
> > > +extern void ceph_debugfs_cleanup_subdir(struct dentry *subdir_dentry);
> > > +
> > >  #endif
> > > 
> > > diff --git a/net/ceph/debugfs.c b/net/ceph/debugfs.c
> > > index 2110439f8a24..cd6f69dd97fa 100644
> > > --- a/net/ceph/debugfs.c
> > > +++ b/net/ceph/debugfs.c
> > > @@ -404,6 +404,18 @@ void ceph_debugfs_cleanup(void)
> > >       debugfs_remove(ceph_debugfs_dir);
> > >  }
> > > 
> > > +struct dentry *ceph_debugfs_create_subdir(const char *subdir)
> > > +{
> > > +     return debugfs_create_dir(subdir, ceph_debugfs_dir);
> > > +}
> > > +EXPORT_SYMBOL(ceph_debugfs_create_subdir);
> > > +
> > > +void ceph_debugfs_cleanup_subdir(struct dentry *subdir_dentry)
> > > +{
> > > +     debugfs_remove(subdir_dentry);
> > > +}
> > > +EXPORT_SYMBOL(ceph_debugfs_cleanup_subdir);
> > > +
> > 
> > Rather than these specialized helpers, I think it'd be cleaner/more
> > evident to just export the ceph_debugfs_dir symbol and then use normal
> > debugfs commands in ceph.ko.
> 
> I had initially thought of doing that, but was concerned about putting
> ceph_debugfs_dir to abuse once exported.
> 

I wouldn't worry about that. The only external user of this symbol will
be in ceph.ko and we'll vet any code that goes in there.

> > 
> > >  void ceph_debugfs_client_init(struct ceph_client *client)
> > >  {
> > >       char name[80];
> > > @@ -413,7 +425,7 @@ void ceph_debugfs_client_init(struct ceph_client *client)
> > > 
> > >       dout("ceph_debugfs_client_init %p %s\n", client, name);
> > > 
> > > -     client->debugfs_dir = debugfs_create_dir(name, ceph_debugfs_dir);
> > > +     client->debugfs_dir = ceph_debugfs_create_subdir(name);
> > > 
> > >       client->monc.debugfs_file = debugfs_create_file("monc",
> > >                                                     0400,
> > > @@ -454,7 +466,7 @@ void ceph_debugfs_client_cleanup(struct ceph_client *client)
> > >       debugfs_remove(client->debugfs_monmap);
> > >       debugfs_remove(client->osdc.debugfs_file);
> > >       debugfs_remove(client->monc.debugfs_file);
> > > -     debugfs_remove(client->debugfs_dir);
> > > +     ceph_debugfs_cleanup_subdir(client->debugfs_dir);
> > >  }
> > > 
> > >  #else  /* CONFIG_DEBUG_FS */
> > > @@ -475,4 +487,15 @@ void ceph_debugfs_client_cleanup(struct ceph_client *client)
> > >  {
> > >  }
> > > 
> > > +struct dentry *ceph_debugfs_create_subdir(const char *subdir)
> > > +{
> > > +     return NULL;
> > > +}
> > > +EXPORT_SYMBOL(ceph_debugfs_create_subdir);
> > > +
> > > +void ceph_debugfs_cleanup_subdir(struct dentry *subdir_dentry)
> > > +{
> > > +}
> > > +EXPORT_SYMBOL(ceph_debugfs_cleanup_subdir);
> > > +
> > >  #endif  /* CONFIG_DEBUG_FS */
> > 
> > --
> > Jeff Layton <jlayton@redhat.com>
> > 
> 
> 

-- 
Jeff Layton <jlayton@redhat.com>