linux-kernel - Re: [PATCH] eventfs: Stop using dcache

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Date: Wed, 3 Jan 2024 13:54:36 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Steven Rostedt <rostedt@...dmis.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>, Al Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] eventfs: Stop using dcache_readdir() for getdents()

On Wed, 3 Jan 2024 at 11:57, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Or, you know, you could do what I've told you to do at least TEN TIMES
> already, which is to not mess with any of this, and just implement the
> '->permission()' callback (and getattr() to just make 'ls' look sane
> too, rather than silently saying "we'll act as if gid is set right,
> but not show it").

Actually, an even simpler option might be to just do this all at
d_revalidate() time.

Here's an updated patch that builds, and is PURELY AN EXAMPLE. I think
it "works", but it currently always resets the inode mode/uid/gid
unconditionally, which is wrong - it should not do so if the inode has
been manually set.

So take this as a "this might work", but it probably needs a bit more
work - eventfs_set_attr() should set some bit in the inode to say
"these have been set manually", and then revalidate would say "I'll
not touch inodes that have that bit set".

Or something.

Anyway, this patch is nwo relative to your latest pull request, so it
has the check for dentry->d_inode in set_gid() (and still removes the
whole function).

Again: UNTESTED, and meant as a "this is another way to avoid messing
with the dentry tree manually, and just using the VFS interfaces we
already have"

               Linus

View attachment "patch.diff" of type "text/x-patch" (5197 bytes)