Revert "bcache: add "clock" cache replacement policy"

This reverts commit 55766dbc11bf6cb8516819a45a39544b967090f3.

The interim patch has been replaced by an official commit
70bc173ce06be90b026bb00ea175567c91f006e4 bcache: reduce gc latency by processing less nodes and sleep less time

BUG=b/466158659
TEST=presubmit
RELEASE_NOTE=None

cos-patch: bug
Change-Id: I6dd97afc07e365b0e9da27c7932034ec5be8723d
Signed-off-by: He Gao <hegao@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/121927
Reviewed-by: Miri Amarilio <mirilio@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/122027

Documentation/admin-guide/bcache.rst

diff --git a/Documentation/admin-guide/bcache.rst b/Documentation/admin-guide/bcache.rst
index 2be2999..6fdb495 100644
--- a/Documentation/admin-guide/bcache.rst
+++ b/Documentation/admin-guide/bcache.rst
@@ -616,7 +616,7 @@
   Size of buckets
 
 cache_replacement_policy
-  One of either lru, fifo, random or clock.
+  One of either lru, fifo or random.
 
 discard
   Boolean; if on a discard/TRIM will be issued to each bucket before it is

drivers/md/bcache/alloc.c

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index fd65431..edb9a0f 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -69,8 +69,7 @@
 #include <linux/random.h>
 #include <trace/events/bcache.h>
 
-#define MAX_OPEN_BUCKETS	128
-#define CHECK_PRIO_SLICES	16
+#define MAX_OPEN_BUCKETS 128
 
 /* Bucket heap / gen */
 
@@ -212,41 +211,19 @@ static void invalidate_buckets_lru(struct cache *ca)
 	}
 }
 
-/*
- * When check_prio is true, this FIFO policy examines the priority of the
- * buckets and invalidates only the ones below a threshold in the priority
- * ladder. As it goes, the threshold will be raised if not enough buckets are
- * invalidated. Empty buckets are also invalidated. This evaulation resembles
- * the LRU policy, and is used to approximate the classic clock-sweep cache
- * replacement algorithm.
- */
-static void invalidate_buckets_fifo(struct cache *ca, bool check_prio)
+static void invalidate_buckets_fifo(struct cache *ca)
 {
 	struct bucket *b;
 	size_t checked = 0;
-	size_t check_quota = 0;
-	uint16_t prio_threshold = ca->set->min_prio;
 
 	while (!fifo_full(&ca->free_inc)) {
 		if (ca->fifo_last_bucket <  ca->sb.first_bucket ||
 		    ca->fifo_last_bucket >= ca->sb.nbuckets)
 			ca->fifo_last_bucket = ca->sb.first_bucket;
 
-		if (check_prio && checked >= check_quota) {
-			BUG_ON(ca->set->min_prio > INITIAL_PRIO);
-			prio_threshold +=
-				DIV_ROUND_UP(INITIAL_PRIO - ca->set->min_prio,
-					     CHECK_PRIO_SLICES);
-			check_quota += DIV_ROUND_UP(ca->sb.nbuckets,
-						    CHECK_PRIO_SLICES);
-		}
-
 		b = ca->buckets + ca->fifo_last_bucket++;
 
-		if (bch_can_invalidate_bucket(ca, b) &&
-		    (!check_prio ||
-		     b->prio <= prio_threshold ||
-		     !GC_SECTORS_USED(b)))
+		if (bch_can_invalidate_bucket(ca, b))
 			bch_invalidate_one_bucket(ca, b);
 
 		if (++checked >= ca->sb.nbuckets) {
@@ -292,14 +269,11 @@ static void invalidate_buckets(struct cache *ca)
 		invalidate_buckets_lru(ca);
 		break;
 	case CACHE_REPLACEMENT_FIFO:
-		invalidate_buckets_fifo(ca, false);
+		invalidate_buckets_fifo(ca);
 		break;
 	case CACHE_REPLACEMENT_RANDOM:
 		invalidate_buckets_random(ca);
 		break;
-	case CACHE_REPLACEMENT_CLOCK:
-		invalidate_buckets_fifo(ca, true);
-		break;
 	}
 }
 

drivers/md/bcache/bcache_ondisk.h

diff --git a/drivers/md/bcache/bcache_ondisk.h b/drivers/md/bcache/bcache_ondisk.h
index d45794e..6620a7f 100644
--- a/drivers/md/bcache/bcache_ondisk.h
+++ b/drivers/md/bcache/bcache_ondisk.h
@@ -288,7 +288,6 @@ BITMASK(CACHE_REPLACEMENT,		struct cache_sb, flags, 2, 3);
 #define CACHE_REPLACEMENT_LRU		0U
 #define CACHE_REPLACEMENT_FIFO		1U
 #define CACHE_REPLACEMENT_RANDOM	2U
-#define CACHE_REPLACEMENT_CLOCK		3U
 
 BITMASK(BDEV_CACHE_MODE,		struct cache_sb, flags, 0, 4);
 #define CACHE_MODE_WRITETHROUGH		0U

drivers/md/bcache/sysfs.c

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index f2d1b2d..b3a34f3 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -45,7 +45,6 @@ static const char * const cache_replacement_policies[] = {
 	"lru",
 	"fifo",
 	"random",
-	"clock",
 	NULL
 };