3 files changed, 39 insertions, 18 deletions

diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index f3403b45bc28..4478ff1e5036 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -825,12 +825,22 @@ unsigned bch_btree_insert_key(struct btree_keys *b, struct bkey *k,
 	struct bset *i = bset_tree_last(b)->data;
 	struct bkey *m, *prev = NULL;
 	struct btree_iter iter;
+	struct bkey preceding_key_on_stack = ZERO_KEY;
+	struct bkey *preceding_key_p = &preceding_key_on_stack;
 
 	BUG_ON(b->ops->is_extents && !KEY_SIZE(k));
 
-	m = bch_btree_iter_init(b, &iter, b->ops->is_extents
-				? PRECEDING_KEY(&START_KEY(k))
-				: PRECEDING_KEY(k));
+	/*
+	 * If k has preceding key, preceding_key_p will be set to address
+	 *  of k's preceding key; otherwise preceding_key_p will be set
+	 * to NULL inside preceding_key().
+	 */
+	if (b->ops->is_extents)
+		preceding_key(&START_KEY(k), &preceding_key_p);
+	else
+		preceding_key(k, &preceding_key_p);
+
+	m = bch_btree_iter_init(b, &iter, preceding_key_p);
 
 	if (b->ops->insert_fixup(b, k, &iter, replace_key))
 		return status;
diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
index b867f2200495..7e21a2087477 100644
--- a/drivers/md/bcache/bset.h
+++ b/drivers/md/bcache/bset.h
@@ -418,20 +418,26 @@ static inline bool bch_cut_back(const struct bkey *where, struct bkey *k)
 	return __bch_cut_back(where, k);
 }
 
-#define PRECEDING_KEY(_k)					\
-({								\
-	struct bkey *_ret = NULL;				\
-								\
-	if (KEY_INODE(_k) || KEY_OFFSET(_k)) {			\
-		_ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0);	\
-								\
-		if (!_ret->low)					\
-			_ret->high--;				\
-		_ret->low--;					\
-	}							\
-								\
-	_ret;							\
-})
+/*
+ * Pointer '*preceding_key_p' points to a memory object to store preceding
+ * key of k. If the preceding key does not exist, set '*preceding_key_p' to
+ * NULL. So the caller of preceding_key() needs to take care of memory
+ * which '*preceding_key_p' pointed to before calling preceding_key().
+ * Currently the only caller of preceding_key() is bch_btree_insert_key(),
+ * and it points to an on-stack variable, so the memory release is handled
+ * by stackframe itself.
+ */
+static inline void preceding_key(struct bkey *k, struct bkey **preceding_key_p)
+{
+	if (KEY_INODE(k) || KEY_OFFSET(k)) {
+		(**preceding_key_p) = KEY(KEY_INODE(k), KEY_OFFSET(k), 0);
+		if (!(*preceding_key_p)->low)
+			(*preceding_key_p)->high--;
+		(*preceding_key_p)->low--;
+	} else {
+		(*preceding_key_p) = NULL;
+	}
+}
 
 static inline bool bch_ptr_invalid(struct btree_keys *b, const struct bkey *k)
 {
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index c591347150d6..22cfc976c12a 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -372,8 +372,13 @@ STORE(bch_cached_dev)
 	if (attr == &sysfs_writeback_running)
 		bch_writeback_queue(dc);
 
+	/*
+	 * Only set BCACHE_DEV_WB_RUNNING when cached device attached to
+	 * a cache set, otherwise it doesn't make sense.
+	 */
 	if (attr == &sysfs_writeback_percent)
-		if (!test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
+		if ((dc->disk.c != NULL) &&
+		    (!test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)))
 			schedule_delayed_work(&dc->writeback_rate_update,
 				      dc->writeback_rate_update_seconds * HZ);