Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 954dad2..013e35a 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -627,6 +627,20 @@
 	struct bkey		gc_done;
 
 	/*
+	 * For automatical garbage collection after writeback completed, this
+	 * varialbe is used as bit fields,
+	 * - 0000 0001b (BCH_ENABLE_AUTO_GC): enable gc after writeback
+	 * - 0000 0010b (BCH_DO_AUTO_GC):     do gc after writeback
+	 * This is an optimization for following write request after writeback
+	 * finished, but read hit rate dropped due to clean data on cache is
+	 * discarded. Unless user explicitly sets it via sysfs, it won't be
+	 * enabled.
+	 */
+#define BCH_ENABLE_AUTO_GC	1
+#define BCH_DO_AUTO_GC		2
+	uint8_t			gc_after_writeback;
+
+	/*
 	 * The allocation code needs gc_mark in struct bucket to be correct, but
 	 * it's not while a gc is in progress. Protected by bucket_lock.
 	 */
@@ -658,7 +672,11 @@
 
 	/*
 	 * A btree node on disk could have too many bsets for an iterator to fit
-	 * on the stack - have to dynamically allocate them
+	 * on the stack - have to dynamically allocate them.
+	 * bch_cache_set_alloc() will make sure the pool can allocate iterators
+	 * equipped with enough room that can host
+	 *     (sb.bucket_size / sb.block_size)
+	 * btree_iter_sets, which is more than static MAX_BSETS.
 	 */
 	mempool_t		fill_iter;
 
@@ -687,8 +705,8 @@
 	atomic_long_t		writeback_keys_failed;
 
 	atomic_long_t		reclaim;
+	atomic_long_t		reclaimed_journal_buckets;
 	atomic_long_t		flush_write;
-	atomic_long_t		retry_flush_write;
 
 	enum			{
 		ON_ERROR_UNREGISTER,
@@ -708,8 +726,6 @@
 
 #define BUCKET_HASH_BITS	12
 	struct hlist_head	bucket_hash[1 << BUCKET_HASH_BITS];
-
-	DECLARE_HEAP(struct btree *, flush_btree);
 };
 
 struct bbio {
@@ -988,7 +1004,7 @@
 int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
 			  uint8_t *set_uuid);
 void bch_cached_dev_detach(struct cached_dev *dc);
-void bch_cached_dev_run(struct cached_dev *dc);
+int bch_cached_dev_run(struct cached_dev *dc);
 void bcache_device_stop(struct bcache_device *d);
 
 void bch_cache_set_unregister(struct cache_set *c);
@@ -1004,7 +1020,7 @@
 int bch_cache_allocator_start(struct cache *ca);
 
 void bch_debug_exit(void);
-void bch_debug_init(struct kobject *kobj);
+void bch_debug_init(void);
 void bch_request_exit(void);
 int bch_request_init(void);