On Mon, 04 Jun 2012 15:43:56 +0200, Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx> wrote:
+/*
+ * Returns true if MIGRATE_UNMOVABLE pageblock can be successfully
+ * converted to MIGRATE_MOVABLE type, false otherwise.
+ */
+static bool can_rescue_unmovable_pageblock(struct page *page, bool locked)
+{
+ unsigned long pfn, start_pfn, end_pfn;
+ struct page *start_page, *end_page, *cursor_page;
+
+ pfn = page_to_pfn(page);
+ start_pfn = pfn & ~(pageblock_nr_pages - 1);
+ end_pfn = start_pfn + pageblock_nr_pages - 1;
+
+ start_page = pfn_to_page(start_pfn);
+ end_page = pfn_to_page(end_pfn);
+
+ for (cursor_page = start_page, pfn = start_pfn; cursor_page <= end_page;
+ pfn++, cursor_page++) {
+ struct zone *zone = page_zone(start_page);
+ unsigned long flags;
+
+ if (!pfn_valid_within(pfn))
+ continue;
+
+ /* Do not deal with pageblocks that overlap zones */
+ if (page_zone(cursor_page) != zone)
+ return false;
+
+ if (!locked)
+ spin_lock_irqsave(&zone->lock, flags);
+
+ if (PageBuddy(cursor_page)) {
+ int order = page_order(cursor_page);
-/* Returns true if the page is within a block suitable for migration to */
-static bool suitable_migration_target(struct page *page)
+ pfn += (1 << order) - 1;
+ cursor_page += (1 << order) - 1;
+
+ if (!locked)
+ spin_unlock_irqrestore(&zone->lock, flags);
+ continue;
+ } else if (page_count(cursor_page) == 0 ||
+ PageLRU(cursor_page)) {
+ if (!locked)
+ spin_unlock_irqrestore(&zone->lock, flags);
+ continue;
+ }
+
+ if (!locked)
+ spin_unlock_irqrestore(&zone->lock, flags);
spin_unlock in three spaces is ugly. How about adding a flag that holds the
result of the function which you use as for loop condition and you set it to
false inside an additional else clause? Eg.:
bool result = true;
for (...; result && cursor_page <= end_page; ...) {
...
if (!pfn_valid_within(pfn)) continue;
if (page_zone(cursor_page) != zone) return false;
if (!locked) spin_lock_irqsave(...);
if (PageBuddy(...)) {
...
} else if (page_count(cursor_page) == 0 ||
PageLRU(cursor_page)) {
...
} else {
result = false;
}
if (!locked) spin_unlock_irqsave(...);
}
return result;
+ return false;
+ }
+
+ return true;
+}
How do you make sure that a page is not allocated while this runs? Or you just
don't care? Not that even with zone lock, page may be allocated from pcp list
on (another) CPU.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +----<email/xmpp: mpn@xxxxxxxxxx>--------------ooO--(_)--Ooo--
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