Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/md/bcache/journal.h b/drivers/md/bcache/journal.h
index 66f0fac..f2ea34d 100644
--- a/drivers/md/bcache/journal.h
+++ b/drivers/md/bcache/journal.h
@@ -103,6 +103,8 @@
 /* Embedded in struct cache_set */
 struct journal {
 	spinlock_t		lock;
+	spinlock_t		flush_write_lock;
+	bool			btree_flushing;
 	/* used when waiting because the journal was full */
 	struct closure_waitlist	wait;
 	struct closure		io;
@@ -154,6 +156,8 @@
 	struct bio_vec		bv[8];
 };
 
+#define BTREE_FLUSH_NR	8
+
 #define journal_pin_cmp(c, l, r)				\
 	(fifo_idx(&(c)->journal.pin, (l)) > fifo_idx(&(c)->journal.pin, (r)))