Commit c1a6c536 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Andrew Morton
Browse files

mm/vmemmap: improve vmemmap_can_optimize and allow architectures to override 

dax vmemmap optimization requires a minimum of 2 PAGE_SIZE area within
vmemmap such that tail page mapping can point to the second PAGE_SIZE
area.  Enforce that in vmemmap_can_optimize() function.

Architectures like powerpc also want to enable vmemmap optimization
conditionally (only with radix MMU translation).  Hence allow architecture
override.

Link: https://lkml.kernel.org/r/20230724190759.483013-4-aneesh.kumar@linux.ibm.com


Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f32928ab

include/linux/mm.h

+23 −4
Original line number Diff line number Diff line
@@ -3632,13 +3632,32 @@ void vmemmap_free(unsigned long start, unsigned long end, 
		struct vmem_altmap *altmap);

#endif



#define VMEMMAP_RESERVE_NR	2

#ifdef CONFIG_ARCH_WANT_OPTIMIZE_VMEMMAP

static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap,

static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap,

					  struct dev_pagemap *pgmap)

{

	return is_power_of_2(sizeof(struct page)) &&

		pgmap && (pgmap_vmemmap_nr(pgmap) > 1) && !altmap;

	unsigned long nr_pages;

	unsigned long nr_vmemmap_pages;



	if (!pgmap || !is_power_of_2(sizeof(struct page)))

		return false;



	nr_pages = pgmap_vmemmap_nr(pgmap);

	nr_vmemmap_pages = ((nr_pages * sizeof(struct page)) >> PAGE_SHIFT);

	/*

	 * For vmemmap optimization with DAX we need minimum 2 vmemmap

	 * pages. See layout diagram in Documentation/mm/vmemmap_dedup.rst

	 */

	return !altmap && (nr_vmemmap_pages > VMEMMAP_RESERVE_NR);

}

/*

 * If we don't have an architecture override, use the generic rule

 */

#ifndef vmemmap_can_optimize

#define vmemmap_can_optimize __vmemmap_can_optimize

#endif



#else

static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap,

					   struct dev_pagemap *pgmap)

mm/mm_init.c

+1 −1
Original line number Diff line number Diff line
@@ -1020,7 +1020,7 @@ static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap, 
	if (!vmemmap_can_optimize(altmap, pgmap))

		return pgmap_vmemmap_nr(pgmap);



	return 2 * (PAGE_SIZE / sizeof(struct page));

	return VMEMMAP_RESERVE_NR * (PAGE_SIZE / sizeof(struct page));

}



static void __ref memmap_init_compound(struct page *head,