Re: [PATCH v2 08/11] x86/mm/pat: remove MEMTYPE_*_MATCH

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

* David Hildenbrand <david@redhat.com> [250512 08:34]:
> The "memramp() shrinking" scenario no longer applies, so let's remove
> that now-unnecessary handling.
> 
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Acked-by: Ingo Molnar <mingo@kernel.org> # x86 bits
> Signed-off-by: David Hildenbrand <david@redhat.com>

small comment, but this looks good.

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
>  arch/x86/mm/pat/memtype_interval.c | 44 ++++--------------------------
>  1 file changed, 6 insertions(+), 38 deletions(-)
> 
> diff --git a/arch/x86/mm/pat/memtype_interval.c b/arch/x86/mm/pat/memtype_interval.c
> index 645613d59942a..9d03f0dbc4715 100644
> --- a/arch/x86/mm/pat/memtype_interval.c
> +++ b/arch/x86/mm/pat/memtype_interval.c
> @@ -49,26 +49,15 @@ INTERVAL_TREE_DEFINE(struct memtype, rb, u64, subtree_max_end,
>  
>  static struct rb_root_cached memtype_rbroot = RB_ROOT_CACHED;
>  
> -enum {
> -	MEMTYPE_EXACT_MATCH	= 0,
> -	MEMTYPE_END_MATCH	= 1
> -};
> -
> -static struct memtype *memtype_match(u64 start, u64 end, int match_type)
> +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) {

I think this could use interval_tree_for_each_span() instead.

> -		if ((match_type == MEMTYPE_EXACT_MATCH) &&
> -		    (entry_match->start == start) && (entry_match->end == end))
> -			return entry_match;
> -
> -		if ((match_type == MEMTYPE_END_MATCH) &&
> -		    (entry_match->start < start) && (entry_match->end == end))
> +		if (entry_match->start == start && entry_match->end == end)
>  			return entry_match;
> -
>  		entry_match = interval_iter_next(entry_match, start, end-1);
>  	}
>  
> @@ -132,32 +121,11 @@ struct memtype *memtype_erase(u64 start, u64 end)
>  {
>  	struct memtype *entry_old;
>  
> -	/*
> -	 * Since the memtype_rbroot tree allows overlapping ranges,
> -	 * memtype_erase() checks with EXACT_MATCH first, i.e. free
> -	 * a whole node for the munmap case.  If no such entry is found,
> -	 * it then checks with END_MATCH, i.e. shrink the size of a node
> -	 * from the end for the mremap case.
> -	 */
> -	entry_old = memtype_match(start, end, MEMTYPE_EXACT_MATCH);
> -	if (!entry_old) {
> -		entry_old = memtype_match(start, end, MEMTYPE_END_MATCH);
> -		if (!entry_old)
> -			return ERR_PTR(-EINVAL);
> -	}
> -
> -	if (entry_old->start == start) {
> -		/* munmap: erase this node */
> -		interval_remove(entry_old, &memtype_rbroot);
> -	} else {
> -		/* mremap: update the end value of this node */
> -		interval_remove(entry_old, &memtype_rbroot);
> -		entry_old->end = start;
> -		interval_insert(entry_old, &memtype_rbroot);
> -
> -		return NULL;
> -	}
> +	entry_old = memtype_match(start, end);
> +	if (!entry_old)
> +		return ERR_PTR(-EINVAL);
>  
> +	interval_remove(entry_old, &memtype_rbroot);
>  	return entry_old;
>  }
>  
> -- 
> 2.49.0
>