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Subject[PATCH 04/25] mm, compaction: Remove unnecessary zone parameter in some instances
Date
A zone parameter is passed into a number of top-level compaction functions
despite the fact that it's already in cache_control. This is harmless but
it did need an audit to check if zone actually ever changes meaningfully.
This patches removes the parameter in a number of top-level functions. The
change could be much deeper but this was enough to briefly clarify the
flow.

No functional change.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/compaction.c | 54 ++++++++++++++++++++++++++----------------------------
1 file changed, 26 insertions(+), 28 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index fb4d9f52ed56..7acb43f07303 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1300,8 +1300,7 @@ static inline bool is_via_compact_memory(int order)
return order == -1;
}

-static enum compact_result __compact_finished(struct zone *zone,
- struct compact_control *cc)
+static enum compact_result __compact_finished(struct compact_control *cc)
{
unsigned int order;
const int migratetype = cc->migratetype;
@@ -1312,7 +1311,7 @@ static enum compact_result __compact_finished(struct zone *zone,
/* Compaction run completes if the migrate and free scanner meet */
if (compact_scanners_met(cc)) {
/* Let the next compaction start anew. */
- reset_cached_positions(zone);
+ reset_cached_positions(cc->zone);

/*
* Mark that the PG_migrate_skip information should be cleared
@@ -1321,7 +1320,7 @@ static enum compact_result __compact_finished(struct zone *zone,
* based on an allocation request.
*/
if (cc->direct_compaction)
- zone->compact_blockskip_flush = true;
+ cc->zone->compact_blockskip_flush = true;

if (cc->whole_zone)
return COMPACT_COMPLETE;
@@ -1345,7 +1344,7 @@ static enum compact_result __compact_finished(struct zone *zone,

/* Direct compactor: Is a suitable page free? */
for (order = cc->order; order < MAX_ORDER; order++) {
- struct free_area *area = &zone->free_area[order];
+ struct free_area *area = &cc->zone->free_area[order];
bool can_steal;

/* Job done if page is free of the right migratetype */
@@ -1391,13 +1390,12 @@ static enum compact_result __compact_finished(struct zone *zone,
return COMPACT_NO_SUITABLE_PAGE;
}

-static enum compact_result compact_finished(struct zone *zone,
- struct compact_control *cc)
+static enum compact_result compact_finished(struct compact_control *cc)
{
int ret;

- ret = __compact_finished(zone, cc);
- trace_mm_compaction_finished(zone, cc->order, ret);
+ ret = __compact_finished(cc);
+ trace_mm_compaction_finished(cc->zone, cc->order, ret);
if (ret == COMPACT_NO_SUITABLE_PAGE)
ret = COMPACT_CONTINUE;

@@ -1524,16 +1522,16 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
return false;
}

-static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc)
+static enum compact_result compact_zone(struct compact_control *cc)
{
enum compact_result ret;
- unsigned long start_pfn = zone->zone_start_pfn;
- unsigned long end_pfn = zone_end_pfn(zone);
+ unsigned long start_pfn = cc->zone->zone_start_pfn;
+ unsigned long end_pfn = zone_end_pfn(cc->zone);
unsigned long last_migrated_pfn;
const bool sync = cc->mode != MIGRATE_ASYNC;

cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
- ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
+ ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
cc->classzone_idx);
/* Compaction is likely to fail */
if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
@@ -1546,8 +1544,8 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
* Clear pageblock skip if there were failures recently and compaction
* is about to be retried after being deferred.
*/
- if (compaction_restarting(zone, cc->order))
- __reset_isolation_suitable(zone);
+ if (compaction_restarting(cc->zone, cc->order))
+ __reset_isolation_suitable(cc->zone);

/*
* Setup to move all movable pages to the end of the zone. Used cached
@@ -1559,16 +1557,16 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
cc->migrate_pfn = start_pfn;
cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
} else {
- cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
- cc->free_pfn = zone->compact_cached_free_pfn;
+ cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync];
+ cc->free_pfn = cc->zone->compact_cached_free_pfn;
if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
- zone->compact_cached_free_pfn = cc->free_pfn;
+ cc->zone->compact_cached_free_pfn = cc->free_pfn;
}
if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
cc->migrate_pfn = start_pfn;
- zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
- zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
+ cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
+ cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
}

if (cc->migrate_pfn == start_pfn)
@@ -1582,11 +1580,11 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro

migrate_prep_local();

- while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
+ while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
int err;
unsigned long start_pfn = cc->migrate_pfn;

- switch (isolate_migratepages(zone, cc)) {
+ switch (isolate_migratepages(cc->zone, cc)) {
case ISOLATE_ABORT:
ret = COMPACT_CONTENDED;
putback_movable_pages(&cc->migratepages);
@@ -1653,7 +1651,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
if (last_migrated_pfn < current_block_start) {
cpu = get_cpu();
lru_add_drain_cpu(cpu);
- drain_local_pages(zone);
+ drain_local_pages(cc->zone);
put_cpu();
/* No more flushing until we migrate again */
last_migrated_pfn = 0;
@@ -1678,8 +1676,8 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
* Only go back, not forward. The cached pfn might have been
* already reset to zone end in compact_finished()
*/
- if (free_pfn > zone->compact_cached_free_pfn)
- zone->compact_cached_free_pfn = free_pfn;
+ if (free_pfn > cc->zone->compact_cached_free_pfn)
+ cc->zone->compact_cached_free_pfn = free_pfn;
}

count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
@@ -1716,7 +1714,7 @@ static enum compact_result compact_zone_order(struct zone *zone, int order,
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);

- ret = compact_zone(zone, &cc);
+ ret = compact_zone(&cc);

VM_BUG_ON(!list_empty(&cc.freepages));
VM_BUG_ON(!list_empty(&cc.migratepages));
@@ -1834,7 +1832,7 @@ static void compact_node(int nid)
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);

- compact_zone(zone, &cc);
+ compact_zone(&cc);

VM_BUG_ON(!list_empty(&cc.freepages));
VM_BUG_ON(!list_empty(&cc.migratepages));
@@ -1976,7 +1974,7 @@ static void kcompactd_do_work(pg_data_t *pgdat)

if (kthread_should_stop())
return;
- status = compact_zone(zone, &cc);
+ status = compact_zone(&cc);

if (status == COMPACT_SUCCESS) {
compaction_defer_reset(zone, cc.order, false);
--
2.16.4
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