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Date:   Fri, 25 Feb 2022 17:11:00 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        stable@vger.kernel.org
Subject: Re: [for-linus][PATCH 09/13] tracefs: Set the group ownership in
 apply_options() not parse_options()
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References: <20220225165151.824659113@goodmis.org>
 <20220225165219.737025658@goodmis.org>
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On Fri, Feb 25, 2022 at 11:52:00AM -0500, Steven Rostedt wrote:

> @@ -293,6 +292,9 @@ static int tracefs_apply_options(struct super_block *sb)
>  	inode->i_uid = opts->uid;
>  	inode->i_gid = opts->gid;
>  
> +	if (tracefs_mount && tracefs_mount->mnt_root)
> +		set_gid(tracefs_mount->mnt_root, opts->gid);
> +

Umm...  Why bother with tracefs_mount here in the first place?
You have the superblock the operation is applied for - right in the
arguments.

Just make that
	set_gid(sb->s_root, opts->gid);
and be done with that.  Same place in tracefs_apply_options()...

Incidentally, I'm not sure you need to keep ->i_gid assignment - set_gid()
won't miss that inode, so...