From: Michal Nazarewicz mina86@mina86.com
Signed-off-by: Michal Nazarewicz mina86@mina86.com
--- include/linux/page-isolation.h | 4 ++- mm/page_alloc.c | 66 ++++++++++++++++++++++++++++++++++----- 2 files changed, 60 insertions(+), 10 deletions(-)
On Fri, 2011-08-19 at 16:27 +0200, Marek Szyprowski wrote:
+unsigned long alloc_contig_freed_pages(unsigned long start, unsigned long end,
gfp_t flag)+{
- unsigned long pfn = start, count;
- struct page *page;
- struct zone *zone;
- int order;
- VM_BUG_ON(!pfn_valid(start));
- zone = page_zone(pfn_to_page(start));
On Thu, 08 Sep 2011 20:05:52 +0200, Dave Hansen dave@linux.vnet.ibm.com wrote:
This implies that start->end are entirely contained in a single zone. What enforces that? If some higher layer enforces that, I think we probably need at least a VM_BUG_ON() in here and a comment about who enforces it.
- spin_lock_irq(&zone->lock);
- page = pfn_to_page(pfn);
- for (;;) {
VM_BUG_ON(page_count(page) || !PageBuddy(page));list_del(&page->lru);order = page_order(page);zone->free_area[order].nr_free--;rmv_page_order(page);__mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));pfn += 1 << order;if (pfn >= end)break;VM_BUG_ON(!pfn_valid(pfn));page += 1 << order;- }
This 'struct page *'++ stuff is OK, but only for small, aligned areas. For at least some of the sparsemem modes (non-VMEMMAP), you could walk off of the end of the section_mem_map[] when you cross a MAX_ORDER boundary. I'd feel a little bit more comfortable if pfn_to_page() was being done each time, or only occasionally when you cross a section boundary.
Do the attached changes seem to make sense?
I wanted to avoid calling pfn_to_page() each time as it seem fairly expensive in sparsemem and disctontig modes. At the same time, the macro trickery is so that users of sparsemem-vmemmap and flatmem won't have to pay the price.
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h index b2a81fd..003c52f 100644 --- a/include/linux/page-isolation.h +++ b/include/linux/page-isolation.h @@ -46,11 +46,13 @@ static inline void unset_migratetype_isolate(struct page *page) { __unset_migratetype_isolate(page, MIGRATE_MOVABLE); } + +/* The below functions must be run on a range from a single zone. */ extern unsigned long alloc_contig_freed_pages(unsigned long start, unsigned long end, gfp_t flag); extern int alloc_contig_range(unsigned long start, unsigned long end, gfp_t flags, unsigned migratetype); -extern void free_contig_pages(struct page *page, int nr_pages); +extern void free_contig_pages(unsigned long pfn, unsigned nr_pages);
/* * For migration. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 46e78d4..32fda5d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5716,9 +5716,41 @@ out: spin_unlock_irqrestore(&zone->lock, flags); }
+#if defined(CONFIG_FLATMEM) || defined(CONFIG_SPARSEMEM_VMEMMAP) + +/* + * In FLATMEM and CONFIG_SPARSEMEM_VMEMMAP we can safely increment the page + * pointer and get the same value as if we were to get by calling + * pfn_to_page() on incremented pfn counter. + */ +#define __contig_next_page(page, pageblock_left, pfn, increment) \ + ((page) + (increment)) + +#define __contig_first_page(pageblock_left, pfn) pfn_to_page(pfn) + +#else + +/* + * If we cross pageblock boundary, make sure we get a valid page pointer. If + * we are within pageblock, incrementing the pointer is good enough, and is + * a bit of an optimisation. + */ +#define __contig_next_page(page, pageblock_left, pfn, increment) \ + (likely((pageblock_left) -= (increment)) ? (page) + (increment) \ + : (((pageblock_left) = pageblock_nr_pages), pfn_to_page(pfn))) + +#define __contig_first_page(pageblock_left, pfn) ( \ + ((pageblock_left) = pageblock_nr_pages - \ + ((pfn) & (pageblock_nr_pages - 1))), \ + pfn_to_page(pfn)) + + +#endif + unsigned long alloc_contig_freed_pages(unsigned long start, unsigned long end, gfp_t flag) { + unsigned long pageblock_left __unused; unsigned long pfn = start, count; struct page *page; struct zone *zone; @@ -5729,27 +5761,37 @@ unsigned long alloc_contig_freed_pages(unsigned long start, unsigned long end,
spin_lock_irq(&zone->lock);
- page = pfn_to_page(pfn); + page = __contig_first_page(pageblock_left, pfn); for (;;) { - VM_BUG_ON(page_count(page) || !PageBuddy(page)); + VM_BUG_ON(!page_count(page) || !PageBuddy(page) || + page_zone(page) != zone); + list_del(&page->lru); order = page_order(page); + count = 1UL << order; zone->free_area[order].nr_free--; rmv_page_order(page); - __mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order)); - pfn += 1 << order; + __mod_zone_page_state(zone, NR_FREE_PAGES, -(long)count); + + pfn += count; if (pfn >= end) break; VM_BUG_ON(!pfn_valid(pfn)); - page += 1 << order; + + page = __contig_next_page(page, pageblock_left, pfn, count); }
spin_unlock_irq(&zone->lock);
/* After this, pages in the range can be freed one be one */ - page = pfn_to_page(start); - for (count = pfn - start; count; --count, ++page) + count = pfn - start; + pfn = start; + page = __contig_first_page(pageblock_left, pfn); + for (; count; --count) { prep_new_page(page, 0, flag); + ++pfn; + page = __contig_next_page(page, pageblock_left, pfn, 1); + }
return pfn; } @@ -5903,10 +5945,16 @@ done: return ret; }
-void free_contig_pages(struct page *page, int nr_pages) +void free_contig_pages(unsigned long pfn, unsigned nr_pages) { - for (; nr_pages; --nr_pages, ++page) + unsigned long pageblock_left __unused; + struct page *page = __contig_first_page(pageblock_left, pfn); + + while (nr_pages--) { __free_page(page); + ++pfn; + page = __contig_next_page(page, pageblock_left, pfn, 1); + } }
#ifdef CONFIG_MEMORY_HOTREMOVE