linux-kernel - Re: [PATCH bpf-next 2/4] bpf: Make bpf inode storage available to tracing program

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Message-ID: <20241121-wahrsagung-kantholz-97d1717c78b1@brauner>
Date: Thu, 21 Nov 2024 10:04:07 +0100
From: Christian Brauner <brauner@...nel.org>
To: Song Liu <songliubraving@...a.com>
Cc: Song Liu <song@...nel.org>, 
	"bpf@...r.kernel.org" <bpf@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-security-module@...r.kernel.org" <linux-security-module@...r.kernel.org>, Kernel Team <kernel-team@...a.com>, 
	"andrii@...nel.org" <andrii@...nel.org>, "eddyz87@...il.com" <eddyz87@...il.com>, 
	"ast@...nel.org" <ast@...nel.org>, "daniel@...earbox.net" <daniel@...earbox.net>, 
	"martin.lau@...ux.dev" <martin.lau@...ux.dev>, "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>, 
	"jack@...e.cz" <jack@...e.cz>, "kpsingh@...nel.org" <kpsingh@...nel.org>, 
	"mattbobrowski@...gle.com" <mattbobrowski@...gle.com>, "amir73il@...il.com" <amir73il@...il.com>, 
	"repnop@...gle.com" <repnop@...gle.com>, "jlayton@...nel.org" <jlayton@...nel.org>, 
	Josef Bacik <josef@...icpanda.com>, "mic@...ikod.net" <mic@...ikod.net>, 
	"gnoack@...gle.com" <gnoack@...gle.com>
Subject: Re: [PATCH bpf-next 2/4] bpf: Make bpf inode storage available to
 tracing program

On Wed, Nov 13, 2024 at 02:15:20PM +0000, Song Liu wrote:
> Hi Christian, 
> 
> Thanks for your review. 
> 
> > On Nov 13, 2024, at 2:19 AM, Christian Brauner <brauner@...nel.org> wrote:
> [...]
> 
> >> diff --git a/include/linux/fs.h b/include/linux/fs.h
> >> index 3559446279c1..479097e4dd5b 100644
> >> --- a/include/linux/fs.h
> >> +++ b/include/linux/fs.h
> >> @@ -79,6 +79,7 @@ struct fs_context;
> >> struct fs_parameter_spec;
> >> struct fileattr;
> >> struct iomap_ops;
> >> +struct bpf_local_storage;
> >> 
> >> extern void __init inode_init(void);
> >> extern void __init inode_init_early(void);
> >> @@ -648,6 +649,9 @@ struct inode {
> >> #ifdef CONFIG_SECURITY
> >> void *i_security;
> >> #endif
> >> +#ifdef CONFIG_BPF_SYSCALL
> >> + struct bpf_local_storage __rcu *i_bpf_storage;
> >> +#endif
> > 
> > Sorry, we're not growing struct inode for this. It just keeps getting
> > bigger. Last cycle we freed up 8 bytes to shrink it and we're not going
> > to waste them on special-purpose stuff. We already NAKed someone else's
> > pet field here.
> 
> Would it be acceptable if we union i_bpf_storage with i_security?

I have no quarrels with this if this is acceptable to you.