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Subject[PATCH 02/15] mm: compaction: introduce isolate_migratepages_range().
From: Michal Nazarewicz <mina86@mina86.com>

This commit introduces isolate_migratepages_range() function which
extracts functionality from isolate_migratepages() so that it can be
used on arbitrary PFN ranges.

isolate_migratepages() function is implemented as a simple wrapper
around isolate_migratepages_range().

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
---
mm/compaction.c | 75 +++++++++++++++++++++++++++++++++++++++---------------
1 files changed, 54 insertions(+), 21 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 71a58f6..62902b6 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -250,31 +250,34 @@ typedef enum {
ISOLATE_SUCCESS, /* Pages isolated, migrate */
} isolate_migrate_t;

-/*
- * Isolate all pages that can be migrated from the block pointed to by
- * the migrate scanner within compact_control.
+/**
+ * isolate_migratepages_range() - isolate all migrate-able pages in range.
+ * @zone: Zone pages are in.
+ * @cc: Compaction control structure.
+ * @low_pfn: The first PFN of the range.
+ * @end_pfn: The one-past-the-last PFN of the range.
+ *
+ * Isolate all pages that can be migrated from the range specified by
+ * [low_pfn, end_pfn). Returns zero if there is a fatal signal
+ * pending), otherwise PFN of the first page that was not scanned
+ * (which may be both less, equal to or more then end_pfn).
+ *
+ * Assumes that cc->migratepages is empty and cc->nr_migratepages is
+ * zero.
+ *
+ * Apart from cc->migratepages and cc->nr_migratetypes this function
+ * does not modify any cc's fields, in particular it does not modify
+ * (or read for that matter) cc->migrate_pfn.
*/
-static isolate_migrate_t isolate_migratepages(struct zone *zone,
- struct compact_control *cc)
+static unsigned long
+isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
+ unsigned long low_pfn, unsigned long end_pfn)
{
- unsigned long low_pfn, end_pfn;
unsigned long last_pageblock_nr = 0, pageblock_nr;
unsigned long nr_scanned = 0, nr_isolated = 0;
struct list_head *migratelist = &cc->migratepages;
isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;

- /* Do not scan outside zone boundaries */
- low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
-
- /* Only scan within a pageblock boundary */
- end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
-
- /* Do not cross the free scanner or scan within a memory hole */
- if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
- cc->migrate_pfn = end_pfn;
- return ISOLATE_NONE;
- }
-
/*
* Ensure that there are not too many pages isolated from the LRU
* list by either parallel reclaimers or compaction. If there are,
@@ -283,12 +286,12 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
while (unlikely(too_many_isolated(zone))) {
/* async migration should just abort */
if (!cc->sync)
- return ISOLATE_ABORT;
+ return 0;

congestion_wait(BLK_RW_ASYNC, HZ/10);

if (fatal_signal_pending(current))
- return ISOLATE_ABORT;
+ return 0;
}

/* Time to isolate some pages for migration */
@@ -374,10 +377,40 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
acct_isolated(zone, cc);

spin_unlock_irq(&zone->lru_lock);
- cc->migrate_pfn = low_pfn;

trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);

+ return low_pfn;
+}
+
+/*
+ * Isolate all pages that can be migrated from the block pointed to by
+ * the migrate scanner within compact_control.
+ */
+static isolate_migrate_t isolate_migratepages(struct zone *zone,
+ struct compact_control *cc)
+{
+ unsigned long low_pfn, end_pfn;
+
+ /* Do not scan outside zone boundaries */
+ low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
+
+ /* Only scan within a pageblock boundary */
+ end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
+
+ /* Do not cross the free scanner or scan within a memory hole */
+ if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
+ cc->migrate_pfn = end_pfn;
+ return ISOLATE_NONE;
+ }
+
+ /* Perform the isolation */
+ low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn);
+ if (!low_pfn)
+ return ISOLATE_ABORT;
+
+ cc->migrate_pfn = low_pfn;
+
return ISOLATE_SUCCESS;
}

--
1.7.1.569.g6f426


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