linux-kernel - Re: [PATCH] tracefs/eventfs: Use root and instance inodes as default ownership

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Date: Wed, 10 Jan 2024 10:52:51 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Christian Brauner <brauner@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>, Al Viro
 <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] tracefs/eventfs: Use root and instance inodes as
 default ownership

On Wed, 10 Jan 2024 08:07:46 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> Or are you saying that I don't need the ".permission" callback, because
> eventfs does it when it creates the inodes? But for eventfs to know what
> the permissions changes are, it uses .getattr and .setattr.

OK, if your main argument is that we do not need .permission, I agree with
you. But that's a trivial change and doesn't affect the complexity that
eventfs is doing. In fact, removing the "permission" check is simply this
patch:

--
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index fdff53d5a1f8..f2af07a857e2 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -192,18 +192,10 @@ static int eventfs_get_attr(struct mnt_idmap *idmap,
 	return 0;
 }
 
-static int eventfs_permission(struct mnt_idmap *idmap,
-			      struct inode *inode, int mask)
-{
-	set_top_events_ownership(inode);
-	return generic_permission(idmap, inode, mask);
-}
-
 static const struct inode_operations eventfs_root_dir_inode_operations = {
 	.lookup		= eventfs_root_lookup,
 	.setattr	= eventfs_set_attr,
 	.getattr	= eventfs_get_attr,
-	.permission	= eventfs_permission,
 };
 
 static const struct inode_operations eventfs_file_inode_operations = {
--

I only did that because Linus mentioned it, and I thought it was needed.
I'll apply this patch too, as it appears to work with this code.

Thanks!

-- Steve