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SubjectRe: [RFC PATCH 2/3] mm: add find_alloc_contig_pages() interface
On Mon, Feb 12, 2018 at 02:20:55PM -0800, Mike Kravetz wrote:
> find_alloc_contig_pages() is a new interface that attempts to locate
> and allocate a contiguous range of pages. It is provided as a more
> convenient interface to the existing alloc_contig_range() interface
> which is used by CMA, memory hotplug and gigantic huge pages.
>
> When attempting to allocate a range of pages, migration is employed
> if possible. There is no guarantee that the routine will succeed.
> So, the user must be prepared for failure and have a fall back plan.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> ---
> include/linux/gfp.h | 12 ++++++++
> mm/page_alloc.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 99 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 1a4582b44d32..456979022956 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -573,6 +573,18 @@ static inline bool pm_suspended_storage(void)
> extern int alloc_contig_range(unsigned long start, unsigned long end,
> unsigned migratetype, gfp_t gfp_mask);
> extern void free_contig_range(unsigned long pfn, unsigned nr_pages);
> +extern struct page *find_alloc_contig_pages(unsigned int order, gfp_t gfp,
> + int nid, nodemask_t *nodemask);
> +extern void free_contig_pages(struct page *page, unsigned nr_pages);
> +#else
> +static inline page *find_alloc_contig_pages(unsigned int order, gfp_t gfp,
> + int nid, nodemask_t *nodemask)
> +{
> + return NULL;
> +}
> +static void free_contig_pages(struct page *page, unsigned nr_pages)
> +{
> +}
> #endif
>
> #ifdef CONFIG_CMA
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 064458f317bf..0a5a547acdbf 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -67,6 +67,7 @@
> #include <linux/ftrace.h>
> #include <linux/lockdep.h>
> #include <linux/nmi.h>
> +#include <linux/mmzone.h>
>
> #include <asm/sections.h>
> #include <asm/tlbflush.h>
> @@ -1873,9 +1874,13 @@ static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone,
> {
> return __rmqueue_smallest(zone, order, MIGRATE_CMA);
> }
> +#define contig_alloc_migratetype_ok(migratetype) \
> + ((migratetype) == MIGRATE_CMA || (migratetype) == MIGRATE_MOVABLE)
> #else
> static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
> unsigned int order) { return NULL; }
> +#define contig_alloc_migratetype_ok(migratetype) \
> + ((migratetype) == MIGRATE_MOVABLE)
> #endif
>
> /*
> @@ -7633,6 +7638,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> };
> INIT_LIST_HEAD(&cc.migratepages);
>
> + if (!contig_alloc_migratetype_ok(migratetype))
> + return -EINVAL;
> +
> /*
> * What we do here is we mark all pageblocks in range as
> * MIGRATE_ISOLATE. Because pageblock and max order pages may
> @@ -7723,8 +7731,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>
> /* Make sure the range is really isolated. */
> if (test_pages_isolated(outer_start, end, false)) {
> - pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n",
> - __func__, outer_start, end);
> + if (!(migratetype == MIGRATE_MOVABLE)) /* only print for CMA */
> + pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n",
> + __func__, outer_start, end);
> ret = -EBUSY;
> goto done;
> }
> @@ -7760,6 +7769,82 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
> }
> WARN(count != 0, "%d pages are still in use!\n", count);
> }
> +
> +static bool contig_pfn_range_valid(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++) {
> + if (!pfn_valid(i))
> + return false;
> +
> + page = pfn_to_page(i);
> +
> + if (page_zone(page) != z)
> + return false;
> +
> + }
> +
> + return true;
> +}
> +
> +/**
> + * find_alloc_contig_pages() -- attempt to find and allocate a contiguous
> + * range of pages
> + * @order: number of pages
> + * @gfp: gfp mask used to limit search as well as during compaction
> + * @nid: target node
> + * @nodemask: mask of other possible nodes
> + *
> + * Returns pointer to 'order' pages on success, or NULL if not successful.

Please s/Returns/Return:/ and move the return value description to the end
of the comment block.

> + *
> + * Pages can be freed with a call to free_contig_pages(), or by manually
> + * calling __free_page() for each page allocated.
> + */
> +struct page *find_alloc_contig_pages(unsigned int order, gfp_t gfp,
> + int nid, nodemask_t *nodemask)
> +{
> + unsigned long pfn, nr_pages, flags;
> + struct page *ret_page = NULL;
> + struct zonelist *zonelist;
> + struct zoneref *z;
> + struct zone *zone;
> + int rc;
> +
> + nr_pages = 1 << order;
> + zonelist = node_zonelist(nid, gfp);
> + for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp),
> + nodemask) {
> + spin_lock_irqsave(&zone->lock, flags);
> + pfn = ALIGN(zone->zone_start_pfn, nr_pages);
> + while (zone_spans_pfn(zone, pfn + nr_pages - 1)) {
> + if (contig_pfn_range_valid(zone, pfn, nr_pages)) {
> + spin_unlock_irqrestore(&zone->lock, flags);
> +
> + rc = alloc_contig_range(pfn, pfn + nr_pages,
> + MIGRATE_MOVABLE, gfp);
> + if (!rc) {
> + ret_page = pfn_to_page(pfn);
> + return ret_page;
> + }
> + spin_lock_irqsave(&zone->lock, flags);
> + }
> + pfn += nr_pages;
> + }
> + spin_unlock_irqrestore(&zone->lock, flags);
> + }
> +
> + return ret_page;
> +}
> +EXPORT_SYMBOL_GPL(find_alloc_contig_pages);
> +
> +void free_contig_pages(struct page *page, unsigned nr_pages)
> +{
> + free_contig_range(page_to_pfn(page), nr_pages);
> +}
> +EXPORT_SYMBOL_GPL(free_contig_pages);
> #endif
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> --
> 2.13.6
>
> --
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>

--
Sincerely yours,
Mike.

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