linux-kernel - Re: [PATCH] binder: fix redefinition of seq

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Date:   Thu, 7 Jul 2022 21:21:52 +0000
From:   Carlos Llamas <cmllamas@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Christian Brauner <brauner@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] binder: fix redefinition of seq_file attributes

On Mon, Jul 04, 2022 at 06:13:40PM +0200, Greg Kroah-Hartman wrote:
> On Fri, Jul 01, 2022 at 06:20:41PM +0000, Carlos Llamas wrote:
> > +	binder_for_each_debugfs_entry(db_entry) {
> > +		dentry = binderfs_create_file(binder_logs_root_dir,
> > +					      db_entry->name,
> > +					      db_entry->fops,
> > +					      db_entry->data);
> > +		if (IS_ERR(dentry)) {
> > +			ret = PTR_ERR(dentry);
> > +			goto out;
> > +		}
> 
> I know this is a copy of what is there already, but there is never a
> need to check the result of a debugfs_create_* call.  Just call it and
> move on, never "abort" based on the result of a debugfs call, that's not
> a good idea.

This is true, none of these debugfs files seem critical for mounting a
binderfs instance. I'm thinking init_binder_logs() should just return
void. I'm only a bit hesitant to completely ignore the return code as
users specifically ask for these files to be created via mount option
"stats". So probably a pr_warn is what is actually needed here.

> 
> So can you change this here, or want to send a follow-on patch that
> removes these checks?

Sure, I'll send a follow-on patch. I'm currently AFK so setting ETA for
next week until I can actually test this change.

> 
> >  	}
> >  
> >  	proc_log_dir = binderfs_create_dir(binder_logs_root_dir, "proc");
> 
> Also there's never a need to save a directory, you can always look it up
> when you want to remove it.

It seems this is a convenient way to share this path with binder which
otherwise doesn't know where binderfs was mounted. From having a quick
look it doesn't seem that we need to share all the details in struct
binderfs_info though. Maybe there is a better way to handle all this.

Christian, since this is binderfs area WDYT?

--
Carlos Llamas