linux-kernel - Re: [PATCH v2 09/11] x86/mm/pat: inline memtype_match() into memtype

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Message-ID: <81aa38a0-ae35-41b1-900a-cc60f5367d06@lucifer.local>
Date: Mon, 12 May 2025 17:49:49 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-trace-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tursulin@...ulin.net>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Pedro Falcato <pfalcato@...e.de>, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH v2 09/11] x86/mm/pat: inline memtype_match() into
 memtype_erase()

On Mon, May 12, 2025 at 02:34:22PM +0200, David Hildenbrand wrote:
> Let's just have it in a single function. The resulting function is
> certainly small enough and readable.
>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Nice, great bit of refactoring :) the new version is considerably clearer.

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  arch/x86/mm/pat/memtype_interval.c | 33 +++++++++---------------------
>  1 file changed, 10 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/mm/pat/memtype_interval.c b/arch/x86/mm/pat/memtype_interval.c
> index 9d03f0dbc4715..e5844ed1311ed 100644
> --- a/arch/x86/mm/pat/memtype_interval.c
> +++ b/arch/x86/mm/pat/memtype_interval.c
> @@ -49,21 +49,6 @@ INTERVAL_TREE_DEFINE(struct memtype, rb, u64, subtree_max_end,
>
>  static struct rb_root_cached memtype_rbroot = RB_ROOT_CACHED;
>
> -static struct memtype *memtype_match(u64 start, u64 end)
> -{
> -	struct memtype *entry_match;
> -
> -	entry_match = interval_iter_first(&memtype_rbroot, start, end-1);
> -
> -	while (entry_match != NULL && entry_match->start < end) {
> -		if (entry_match->start == start && entry_match->end == end)
> -			return entry_match;
> -		entry_match = interval_iter_next(entry_match, start, end-1);
> -	}
> -
> -	return NULL; /* Returns NULL if there is no match */
> -}
> -
>  static int memtype_check_conflict(u64 start, u64 end,
>  				  enum page_cache_mode reqtype,
>  				  enum page_cache_mode *newtype)
> @@ -119,14 +104,16 @@ int memtype_check_insert(struct memtype *entry_new, enum page_cache_mode *ret_ty
>
>  struct memtype *memtype_erase(u64 start, u64 end)
>  {
> -	struct memtype *entry_old;
> -
> -	entry_old = memtype_match(start, end);
> -	if (!entry_old)
> -		return ERR_PTR(-EINVAL);
> -
> -	interval_remove(entry_old, &memtype_rbroot);
> -	return entry_old;
> +	struct memtype *entry = interval_iter_first(&memtype_rbroot, start, end - 1);
> +
> +	while (entry && entry->start < end) {
> +		if (entry->start == start && entry->end == end) {
> +			interval_remove(entry, &memtype_rbroot);
> +			return entry;
> +		}
> +		entry = interval_iter_next(entry, start, end - 1);
> +	}
> +	return ERR_PTR(-EINVAL);
>  }
>
>  struct memtype *memtype_lookup(u64 addr)
> --
> 2.49.0
>