[PATCH 3/3] bcache: Fix the tail IO latency regression due to the use of lib min_heap

[Robert Pang <robertpang@google.com>]

In commit "lib/min_heap: introduce non-inline versions of min heap API functions"
(92a8b22), bcache migrates to the generic lib min_heap for all heap operations.
This causes sizeable the tail IO latency regression during the cache replacement.

This commit updates invalidate_buckets_lru() to use the alternative APIs that
sift down elements using the top-down approach like bcache's own original heap
implementation.

[1] https://lore.kernel.org/linux-bcache/wtfuhfntbi6yorxqtpcs4vg5w67mvyckp2a6jmxuzt2hvbw65t@gznwsae5653d/T/#me50a9ddd0386ce602b2f17415e02d33b8e29f533

Signed-off-by: Robert Pang <robertpang@google.com>
---
 drivers/md/bcache/alloc.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 8998e61efa40..547d1cd0c7c2 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -207,15 +207,15 @@ static void invalidate_buckets_lru(struct cache *ca)
 		if (!bch_can_invalidate_bucket(ca, b))
 			continue;
 
-		if (!min_heap_full(&ca->heap))
-			min_heap_push(&ca->heap, &b, &bucket_max_cmp_callback, ca);
-		else if (!new_bucket_max_cmp(&b, min_heap_peek(&ca->heap), ca)) {
+		if (!min_heap_full_inline(&ca->heap))
+			min_heap_push_inline(&ca->heap, &b, &bucket_max_cmp_callback, ca);
+		else if (!new_bucket_max_cmp(&b, min_heap_peek_inline(&ca->heap), ca)) {
 			ca->heap.data[0] = b;
-			min_heap_sift_down(&ca->heap, 0, &bucket_max_cmp_callback, ca);
+			min_heap_sift_down_top_down_inline(&ca->heap, 0, &bucket_max_cmp_callback, ca);
 		}
 	}
 
-	min_heapify_all(&ca->heap, &bucket_min_cmp_callback, ca);
+	min_heapify_all_top_down_inline(&ca->heap, &bucket_min_cmp_callback, ca);
 
 	while (!fifo_full(&ca->free_inc)) {
 		if (!ca->heap.nr) {
@@ -227,8 +227,8 @@ static void invalidate_buckets_lru(struct cache *ca)
 			wake_up_gc(ca->set);
 			return;
 		}
-		b = min_heap_peek(&ca->heap)[0];
-		min_heap_pop(&ca->heap, &bucket_min_cmp_callback, ca);
+		b = min_heap_peek_inline(&ca->heap)[0];
+		min_heap_pop_top_down_inline(&ca->heap, &bucket_min_cmp_callback, ca);
 
 		bch_invalidate_one_bucket(ca, b);
 	}
-- 
2.50.0.rc1.591.g9c95f17f64-goog