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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: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Christophe 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Aneesh Kumar K.V 2023-07-25 00:37:49 +05:30 committed by Andrew Morton
parent f32928ab6f
commit c1a6c536fb
2 changed files with 24 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
include/linux/mm.h
View File

@ -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,
struct dev_pagemap *pgmap)
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)

2
mm/mm_init.c
View File

@ -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,