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SubjectRe: [PATCH] mm/page_alloc: Make alloc_gigantic_page() available for general use
On Wed 16-10-19 13:04:53, Anshuman Khandual wrote:
> HugeTLB helper alloc_gigantic_page() implements fairly generic allocation
> method where it scans over various zones looking for a large contiguous pfn
> range before trying to allocate it with alloc_contig_range(). Other than
> deriving the requested order from 'struct hstate', there is nothing HugeTLB
> specific in there. This can be made available for general use to allocate
> contiguous memory which could not have been allocated through the buddy
> allocator.
>
> alloc_gigantic_page() has been split carving out actual allocation method
> which is then made available via new alloc_contig_pages() helper wrapped
> under CONFIG_CONTIG_ALLOC. All references to 'gigantic' have been replaced
> with more generic term 'contig'. Allocated pages here should be freed with
> free_contig_range() or by calling __free_page() on each allocated page.

Do we want to export this to modules? Apart from mostly styling issues
pointed by David this looks fine.

I do agree that a general allocator api belongs to page_alloc.c rather
than force people to invent their own and broken instances.

> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Mike Rapoport <rppt@linux.ibm.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Pavel Tatashin <pavel.tatashin@microsoft.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

After other issues mentioned by David get resolved you can add
Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> This is based on https://patchwork.kernel.org/patch/11190213/
>
> Changes from [V5,1/2] mm/hugetlb: Make alloc_gigantic_page()...
>
> - alloc_contig_page() takes nr_pages instead of order per Michal
> - s/gigantic/contig on all related functions
>
> include/linux/gfp.h | 2 +
> mm/hugetlb.c | 77 +----------------------------------
> mm/page_alloc.c | 97 +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 101 insertions(+), 75 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index fb07b503dc45..1a11d4857027 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -589,6 +589,8 @@ static inline bool pm_suspended_storage(void)
> /* The below functions must be run on a range from a single zone. */
> extern int alloc_contig_range(unsigned long start, unsigned long end,
> unsigned migratetype, gfp_t gfp_mask);
> +extern struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
> + int nid, nodemask_t *nodemask);
> #endif
> void free_contig_range(unsigned long pfn, unsigned int nr_pages);
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 985ee15eb04b..a5c2c880af27 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1023,85 +1023,12 @@ static void free_gigantic_page(struct page *page, unsigned int order)
> }
>
> #ifdef CONFIG_CONTIG_ALLOC
> -static int __alloc_gigantic_page(unsigned long start_pfn,
> - unsigned long nr_pages, gfp_t gfp_mask)
> -{
> - unsigned long end_pfn = start_pfn + nr_pages;
> - return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
> - gfp_mask);
> -}
> -
> -static bool pfn_range_valid_gigantic(struct zone *z,
> - unsigned long start_pfn, unsigned long nr_pages)
> -{
> - unsigned long i, end_pfn = start_pfn + nr_pages;
> - struct page *page;
> -
> - for (i = start_pfn; i < end_pfn; i++) {
> - page = pfn_to_online_page(i);
> - if (!page)
> - return false;
> -
> - if (page_zone(page) != z)
> - return false;
> -
> - if (PageReserved(page))
> - return false;
> -
> - if (page_count(page) > 0)
> - return false;
> -
> - if (PageHuge(page))
> - return false;
> - }
> -
> - return true;
> -}
> -
> -static bool zone_spans_last_pfn(const struct zone *zone,
> - unsigned long start_pfn, unsigned long nr_pages)
> -{
> - unsigned long last_pfn = start_pfn + nr_pages - 1;
> - return zone_spans_pfn(zone, last_pfn);
> -}
> -
> static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
> int nid, nodemask_t *nodemask)
> {
> - unsigned int order = huge_page_order(h);
> - unsigned long nr_pages = 1 << order;
> - unsigned long ret, pfn, flags;
> - struct zonelist *zonelist;
> - struct zone *zone;
> - struct zoneref *z;
> -
> - zonelist = node_zonelist(nid, gfp_mask);
> - for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nodemask) {
> - spin_lock_irqsave(&zone->lock, flags);
> + unsigned long nr_pages = 1UL << huge_page_order(h);
>
> - pfn = ALIGN(zone->zone_start_pfn, nr_pages);
> - while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
> - if (pfn_range_valid_gigantic(zone, pfn, nr_pages)) {
> - /*
> - * We release the zone lock here because
> - * alloc_contig_range() will also lock the zone
> - * at some point. If there's an allocation
> - * spinning on this lock, it may win the race
> - * and cause alloc_contig_range() to fail...
> - */
> - spin_unlock_irqrestore(&zone->lock, flags);
> - ret = __alloc_gigantic_page(pfn, nr_pages, gfp_mask);
> - if (!ret)
> - return pfn_to_page(pfn);
> - spin_lock_irqsave(&zone->lock, flags);
> - }
> - pfn += nr_pages;
> - }
> -
> - spin_unlock_irqrestore(&zone->lock, flags);
> - }
> -
> - return NULL;
> + return alloc_contig_pages(nr_pages, gfp_mask, nid, nodemask);
> }
>
> static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cd1dd0712624..1e084d6acf2f 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8499,6 +8499,103 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> pfn_max_align_up(end), migratetype);
> return ret;
> }
> +
> +static int __alloc_contig_pages(unsigned long start_pfn,
> + unsigned long nr_pages, gfp_t gfp_mask)
> +{
> + unsigned long end_pfn = start_pfn + nr_pages;
> +
> + return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
> + gfp_mask);
> +}
> +
> +static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
> + unsigned long nr_pages)
> +{
> + unsigned long i, end_pfn = start_pfn + nr_pages;
> + struct page *page;
> +
> + for (i = start_pfn; i < end_pfn; i++) {
> + page = pfn_to_online_page(i);
> + if (!page)
> + return false;
> +
> + if (page_zone(page) != z)
> + return false;
> +
> + if (PageReserved(page))
> + return false;
> +
> + if (page_count(page) > 0)
> + return false;
> +
> + if (PageHuge(page))
> + return false;
> + }
> + return true;
> +}
> +
> +static bool zone_spans_last_pfn(const struct zone *zone,
> + unsigned long start_pfn, unsigned long nr_pages)
> +{
> + unsigned long last_pfn = start_pfn + nr_pages - 1;
> +
> + return zone_spans_pfn(zone, last_pfn);
> +}
> +
> +/**
> + * alloc_contig_pages() -- tries to find and allocate contiguous range of pages
> + * @nr_pages: Number of contiguous pages to allocate
> + * @gfp_mask: GFP mask to limit search and used during compaction
> + * @nid: Target node
> + * @nodemask: Mask for other possible nodes
> + *
> + * This routine is an wrapper around alloc_contig_range(). It scans over zones
> + * on an applicable zonelist to find a contiguous pfn range which can then be
> + * tried for allocation with alloc_contig_range(). This routine is intended
> + * for allocation requests which can not be fulfilled with buddy allocator.
> + *
> + * Allocated pages can be freed with free_contig_range() or by manually calling
> + * __free_page() on each allocated page.
> + *
> + * Return: pointer to 'order' pages on success, or NULL if not successful.
> + */
> +struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
> + int nid, nodemask_t *nodemask)
> +{
> + unsigned long ret, pfn, flags;
> + struct zonelist *zonelist;
> + struct zone *zone;
> + struct zoneref *z;
> +
> + zonelist = node_zonelist(nid, gfp_mask);
> + for_each_zone_zonelist_nodemask(zone, z, zonelist,
> + gfp_zone(gfp_mask), nodemask) {
> + spin_lock_irqsave(&zone->lock, flags);
> +
> + pfn = ALIGN(zone->zone_start_pfn, nr_pages);
> + while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
> + if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
> + /*
> + * We release the zone lock here because
> + * alloc_contig_range() will also lock the zone
> + * at some point. If there's an allocation
> + * spinning on this lock, it may win the race
> + * and cause alloc_contig_range() to fail...
> + */
> + spin_unlock_irqrestore(&zone->lock, flags);
> + ret = __alloc_contig_pages(pfn, nr_pages,
> + gfp_mask);
> + if (!ret)
> + return pfn_to_page(pfn);
> + spin_lock_irqsave(&zone->lock, flags);
> + }
> + pfn += nr_pages;
> + }
> + spin_unlock_irqrestore(&zone->lock, flags);
> + }
> + return NULL;
> +}
> #endif /* CONFIG_CONTIG_ALLOC */
>
> void free_contig_range(unsigned long pfn, unsigned int nr_pages)
> --
> 2.20.1

--
Michal Hocko
SUSE Labs

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