linux-kernel - [PATCH] bcache: kill macro MAX_CACHES_PER

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Message-Id: <20211029125958.95298-1-linf@wangsu.com>
Date:   Fri, 29 Oct 2021 20:59:58 +0800
From:   Lin Feng <linf@...gsu.com>
To:     colyli@...e.de, kent.overstreet@...il.com
Cc:     linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
        linf@...gsu.com
Subject: [PATCH] bcache: kill macro MAX_CACHES_PER_SET

Commit 697e23495c94f0380c1ed8b11f830b92b64c99ea
("bcache: explicitly make cache_set only have single cache")
explicitly makes a cache_set only have single cache and based on the
fact that historily only one cache is ever used in the cache set, so
macro defination for MAX_CACHES_PER_SET as 8 is misleading now.

In fact it should be redefined to 1 and valid number fo sb.nr_in_set
should be 1 and sb.nr_this_dev should always be 0.

But jset's disk layout replies on MAX_CACHES_PER_SET(8), so replace it
with a hardcoded number 8.

Signed-off-by: Lin Feng <linf@...gsu.com>
---
 drivers/md/bcache/bcache.h  | 2 +-
 drivers/md/bcache/super.c   | 4 +---
 include/uapi/linux/bcache.h | 4 ++--
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 5fc989a6d452..a4a410a178c0 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -833,7 +833,7 @@ static inline uint8_t ptr_stale(struct cache_set *c, const struct bkey *k,
 static inline bool ptr_available(struct cache_set *c, const struct bkey *k,
 				 unsigned int i)
 {
-	return (PTR_DEV(k, i) < MAX_CACHES_PER_SET) && c->cache;
+	return (PTR_DEV(k, i) == 0) && c->cache;
 }
 
 /* Btree key macros */
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index f2874c77ff79..2253044c9289 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -140,9 +140,7 @@ static const char *read_super_common(struct cache_sb *sb,  struct block_device *
 		goto err;
 
 	err = "Bad cache device number in set";
-	if (!sb->nr_in_set ||
-	    sb->nr_in_set <= sb->nr_this_dev ||
-	    sb->nr_in_set > MAX_CACHES_PER_SET)
+	if (sb->nr_in_set != 1 || sb->nr_this_dev != 0)
 		goto err;
 
 	err = "Journal buckets not sequential";
diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h
index cf7399f03b71..4beb3e7826ca 100644
--- a/include/uapi/linux/bcache.h
+++ b/include/uapi/linux/bcache.h
@@ -155,7 +155,6 @@ static inline struct bkey *bkey_idx(const struct bkey *k, unsigned int nr_keys)
 #define SB_LABEL_SIZE			32
 #define SB_JOURNAL_BUCKETS		256U
 /* SB_JOURNAL_BUCKETS must be divisible by BITS_PER_LONG */
-#define MAX_CACHES_PER_SET		8
 
 #define BDEV_DATA_START_DEFAULT		16	/* sectors */
 
@@ -356,7 +355,8 @@ struct jset {
 	__u16			btree_level;
 	__u16			pad[3];
 
-	__u64			prio_bucket[MAX_CACHES_PER_SET];
+	/* only a single cache is available */
+	__u64			prio_bucket[8];
 
 	union {
 		struct bkey	start[0];
-- 
2.31.1