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SubjectRe: [PATCH 5/6] mm/memremap: Rename and consolidate SECTION_SIZE
On Wed 03-04-19 10:00:05, Anshuman Khandual wrote:
> From: Robin Murphy <robin.murphy@arm.com>
>
> Enabling ZONE_DEVICE (through ARCH_HAS_ZONE_DEVICE) for arm64 reveals that
> memremap's internal helpers for sparsemem sections conflict with arm64's
> definitions for hugepages which inherit the name of "sections" from earlier
> versions of the ARM architecture.
>
> Disambiguate memremap by propagating sparsemem's PA_ prefix, to clarify
> that these values are in terms of addresses rather than PFNs (and
> because it's a heck of a lot easier than changing all the arch code).
> SECTION_MASK is unused, so it can just go. While here consolidate single
> instance of PA_SECTION_SIZE from mm/hmm.c as well.
>
> [anshuman: Consolidated mm/hmm.c instance and updated the commit message]

Agreed. mremap shouldn't have redefined SECTION_SIZE in the first place.
This just adds a confusion.

> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> include/linux/mmzone.h | 1 +
> kernel/memremap.c | 10 ++++------
> mm/hmm.c | 2 --
> 3 files changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index fba7741..ed7dd27 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1081,6 +1081,7 @@ static inline unsigned long early_pfn_to_nid(unsigned long pfn)
> * PFN_SECTION_SHIFT pfn to/from section number
> */
> #define PA_SECTION_SHIFT (SECTION_SIZE_BITS)
> +#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
> #define PFN_SECTION_SHIFT (SECTION_SIZE_BITS - PAGE_SHIFT)
>
> #define NR_MEM_SECTIONS (1UL << SECTIONS_SHIFT)
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index a856cb5..dda1367 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -14,8 +14,6 @@
> #include <linux/hmm.h>
>
> static DEFINE_XARRAY(pgmap_array);
> -#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
> -#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
>
> #if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
> vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
> @@ -98,8 +96,8 @@ static void devm_memremap_pages_release(void *data)
> put_page(pfn_to_page(pfn));
>
> /* pages are dead and unused, undo the arch mapping */
> - align_start = res->start & ~(SECTION_SIZE - 1);
> - align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
> + align_start = res->start & ~(PA_SECTION_SIZE - 1);
> + align_size = ALIGN(res->start + resource_size(res), PA_SECTION_SIZE)
> - align_start;
>
> nid = page_to_nid(pfn_to_page(align_start >> PAGE_SHIFT));
> @@ -154,8 +152,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
> if (!pgmap->ref || !pgmap->kill)
> return ERR_PTR(-EINVAL);
>
> - align_start = res->start & ~(SECTION_SIZE - 1);
> - align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
> + align_start = res->start & ~(PA_SECTION_SIZE - 1);
> + align_size = ALIGN(res->start + resource_size(res), PA_SECTION_SIZE)
> - align_start;
> align_end = align_start + align_size - 1;
>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index fe1cd87..ef9e4e6 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -33,8 +33,6 @@
> #include <linux/mmu_notifier.h>
> #include <linux/memory_hotplug.h>
>
> -#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
> -
> #if IS_ENABLED(CONFIG_HMM_MIRROR)
> static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
>
> --
> 2.7.4
>

--
Michal Hocko
SUSE Labs

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