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SubjectRe: [PATCH] mm/page_alloc: Make alloc_gigantic_page() available for general use
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On 10/16/2019 02:28 PM, Michal Hocko wrote:
> 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

Just to confirm. Only the styling issues, right ? pfn_range_valid_contig(),
pfn alignment and zone scanning all remain the same like before ?

> 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
>

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