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Subject[PATCH 1/3] fixup! mm: alloc_contig_freed_pages() added
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From: Michal Nazarewicz <mina86@mina86.com>

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>

---
include/asm-generic/memory_model.h | 17 ++++++++++++++
include/linux/page-isolation.h | 4 ++-
mm/page_alloc.c | 43 +++++++++++++++++++++++++++--------
3 files changed, 53 insertions(+), 11 deletions(-)
> On Wed, 2011-09-21 at 17:19 +0200, Michal Nazarewicz wrote:
>> 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.

On Wed, 21 Sep 2011 17:45:59 +0200, Dave Hansen <dave@linux.vnet.ibm.com> wrote:
> Personally, I'd say the (incredibly minuscule) runtime cost is worth the
> cost of making folks' eyes bleed when they see those macros. I think
> there are some nicer ways to do it.

Yeah. I wasn't amazed by them either.

> Is there a reason you can't logically do?
> page = pfn_to_page(pfn);
> for (;;) {
> if (pfn_to_section_nr(pfn) == pfn_to_section_nr(pfn+1))
> page++;
> else
> page = pfn_to_page(pfn+1);
> }

Done. Thanks for the suggestions!

>> +#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

> For the love of Pete, please make those in to functions if you're going
> to keep them.

That was tricky because they modify pageblock_left. Not relevant now
anyways though.

diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
index fb2d63f..900da88 100644
--- a/include/asm-generic/memory_model.h
+++ b/include/asm-generic/memory_model.h
@@ -69,6 +69,23 @@
})
#endif /* CONFIG_FLATMEM/DISCONTIGMEM/SPARSEMEM */

+#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
+
+/*
+ * Both PFNs must be from the same zone! If this function returns
+ * true, pfn_to_page(pfn1) + (pfn2 - pfn1) == pfn_to_page(pfn2).
+ */
+static inline bool zone_pfn_same_memmap(unsigned long pfn1, unsigned long pfn2)
+{
+ return pfn_to_section_nr(pfn1) == pfn_to_section_nr(pfn2);
+}
+
+#else
+
+#define zone_pfn_same_memmap(pfn1, pfn2) (true)
+
+#endif
+
#define page_to_pfn __page_to_pfn
#define pfn_to_page __pfn_to_page

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..bc200a9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5725,31 +5725,46 @@ unsigned long alloc_contig_freed_pages(unsigned long start, unsigned long end,
int order;

VM_BUG_ON(!pfn_valid(start));
- zone = page_zone(pfn_to_page(start));
+ page = pfn_to_page(start);
+ zone = page_zone(page);

spin_lock_irq(&zone->lock);

- page = pfn_to_page(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;
+
+ if (zone_pfn_same_memmap(pfn - count, pfn))
+ page += count;
+ else
+ page = pfn_to_page(pfn);
}

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;
+ for (page = pfn_to_page(pfn); count; --count) {
prep_new_page(page, 0, flag);
+ ++pfn;
+ if (likely(zone_pfn_same_memmap(pfn - 1, pfn)))
+ ++page;
+ else
+ page = pfn_to_page(pfn);
+ }

return pfn;
}
@@ -5903,10 +5918,18 @@ 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)
+ struct page *page = pfn_to_page(pfn);
+
+ while (nr_pages--) {
__free_page(page);
+ ++pfn;
+ if (likely(zone_pfn_same_memmap(pfn - 1, pfn)))
+ ++page;
+ else
+ page = pfn_to_page(pfn);
+ }
}

#ifdef CONFIG_MEMORY_HOTREMOVE
--
1.7.3.1


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