[PATCH 1/4] mm/compaction: use "spinlock_t *" to record held lock in compact [un]lock functions

[Kemeng Shi]

Make compact_lock_irqsave and compact_unlock_should_abort use
"spinlock_t *" to record held lock.
This is a preparation to use compact_unlock_should_abort in
isolate_migratepages_block to remove repeat code.

Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
---
 mm/compaction.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 9641e2131901..dfef14d3ef78 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -523,22 +523,22 @@ static bool test_and_set_skip(struct compact_control *cc, struct page *page)
  * abort when the current block is finished regardless of success rate.
  * Sync compaction acquires the lock.
  *
- * Always returns true which makes it easier to track lock state in callers.
+ * Always returns lock which makes it easier to track lock state in callers.
  */
-static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
+static spinlock_t *compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
 						struct compact_control *cc)
 	__acquires(lock)
 {
 	/* Track if the lock is contended in async mode */
 	if (cc->mode == MIGRATE_ASYNC && !cc->contended) {
 		if (spin_trylock_irqsave(lock, *flags))
-			return true;
+			return lock;
 
 		cc->contended = true;
 	}
 
 	spin_lock_irqsave(lock, *flags);
-	return true;
+	return lock;
 }
 
 /*
@@ -553,12 +553,12 @@ static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
  * Returns true if compaction should abort due to fatal signal pending.
  * Returns false when compaction can continue.
  */
-static bool compact_unlock_should_abort(spinlock_t *lock,
-		unsigned long flags, bool *locked, struct compact_control *cc)
+static bool compact_unlock_should_abort(spinlock_t **locked,
+		unsigned long flags, struct compact_control *cc)
 {
 	if (*locked) {
-		spin_unlock_irqrestore(lock, flags);
-		*locked = false;
+		spin_unlock_irqrestore(*locked, flags);
+		*locked = NULL;
 	}
 
 	if (fatal_signal_pending(current)) {
@@ -586,7 +586,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
 	int nr_scanned = 0, total_isolated = 0;
 	struct page *cursor;
 	unsigned long flags = 0;
-	bool locked = false;
+	spinlock_t *locked = NULL;
 	unsigned long blockpfn = *start_pfn;
 	unsigned int order;
 
@@ -607,8 +607,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
 		 * pending.
 		 */
 		if (!(blockpfn % COMPACT_CLUSTER_MAX)
-		    && compact_unlock_should_abort(&cc->zone->lock, flags,
-								&locked, cc))
+		    && compact_unlock_should_abort(&locked, flags, cc))
 			break;
 
 		nr_scanned++;
@@ -673,7 +672,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
 	}
 
 	if (locked)
-		spin_unlock_irqrestore(&cc->zone->lock, flags);
+		spin_unlock_irqrestore(locked, flags);
 
 	/*
 	 * There is a tiny chance that we have read bogus compound_order(),
-- 
2.30.0