linux-kernel - Re: [PATCH v6 12/42] x86/resctrl: Move rdt_find_domain() to be visible to arch and fs code

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Message-ID: <Z7cK1FpQCgBVSGHq@arm.com>
Date: Thu, 20 Feb 2025 10:58:28 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: James Morse <james.morse@....com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	H Peter Anvin <hpa@...or.com>, Babu Moger <Babu.Moger@....com>,
	shameerali.kolothum.thodi@...wei.com,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	carl@...amperecomputing.com, lcherian@...vell.com,
	bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
	baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
	dfustini@...libre.com, amitsinght@...vell.com,
	David Hildenbrand <david@...hat.com>,
	Rex Nie <rex.nie@...uarmicro.com>,
	Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>,
	Shanker Donthineni <sdonthineni@...dia.com>
Subject: Re: [PATCH v6 12/42] x86/resctrl: Move rdt_find_domain() to be
 visible to arch and fs code

On Wed, Feb 19, 2025 at 03:24:06PM -0800, Reinette Chatre wrote:
> On 2/7/25 10:17 AM, James Morse wrote:
> > rdt_find_domain() finds a domain given a resource and a cache-id.
> > This is used by both the architecture code and the filesystem code.
> > 
> > After the filesystem code moves to live in /fs/, this helper will no
> > longer be visible.
> > 
> > Move it to the global header file. As its now globally visible, and
> > has only a handful of callers, swap the 'rdt' for 'resctrl'.
[...]
> > --- a/include/linux/resctrl.h
> > +++ b/include/linux/resctrl.h
> > @@ -372,6 +372,40 @@ static inline void resctrl_arch_rmid_read_context_check(void)
> >  		might_sleep();
> >  }
> >  
> > +/**
> > + * resctrl_find_domain() - Search for a domain id in a resource domain list.
> > + * @h:		The domain list to search.
> > + * @id:		The domain id to search for.
> > + * @pos:	A pointer to position in the list id should be inserted.
> > + *
> > + * Search the domain list to find the domain id. If the domain id is
> > + * found, return the domain. NULL otherwise.  If the domain id is not
> > + * found (and NULL returned) then the first domain with id bigger than
> > + * the input id can be returned to the caller via @pos.
> > + */
> > +static inline struct rdt_domain_hdr *resctrl_find_domain(struct list_head *h,
> > +							 int id,
> > +							 struct list_head **pos)
> 
> Could you please provide a motivation for why this needs to be inline now?

It's in a header now, to avoid the compiler complaining about unused
static functions wherever this file is included. The alternative is a
prototype declaration and the actual implementation in a .c file.

(drive-by comment, I don't really understand this subsystem to make a
meaningful contribution)

-- 
Catalin