2 files changed, 67 insertions, 22 deletions

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index a1e3e1fcea6e..8bcd8f1bf8cb 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -419,47 +419,87 @@ err:
 
 static void btree_flush_write(struct cache_set *c)
 {
-	/*
-	 * Try to find the btree node with that references the oldest journal
-	 * entry, best is our current candidate and is locked if non NULL:
-	 */
-	struct btree *b, *best;
-	unsigned int i;
+	struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
+	unsigned int i, n;
+
+	if (c->journal.btree_flushing)
+		return;
+
+	spin_lock(&c->journal.flush_write_lock);
+	if (c->journal.btree_flushing) {
+		spin_unlock(&c->journal.flush_write_lock);
+		return;
+	}
+	c->journal.btree_flushing = true;
+	spin_unlock(&c->journal.flush_write_lock);
 
 	atomic_long_inc(&c->flush_write);
-retry:
-	best = NULL;
+	memset(btree_nodes, 0, sizeof(btree_nodes));
+	n = 0;
 
 	mutex_lock(&c->bucket_lock);
-	for_each_cached_btree(b, c, i)
-		if (btree_current_write(b)->journal) {
-			if (!best)
-				best = b;
-			else if (journal_pin_cmp(c,
-					btree_current_write(best)->journal,
-					btree_current_write(b)->journal)) {
-				best = b;
-			}
+	list_for_each_entry_safe_reverse(b, t, &c->btree_cache, list) {
+		if (btree_node_journal_flush(b))
+			pr_err("BUG: flush_write bit should not be set here!");
+
+		mutex_lock(&b->write_lock);
+
+		if (!btree_node_dirty(b)) {
+			mutex_unlock(&b->write_lock);
+			continue;
+		}
+
+		if (!btree_current_write(b)->journal) {
+			mutex_unlock(&b->write_lock);
+			continue;
 		}
 
-	b = best;
-	if (b)
 		set_btree_node_journal_flush(b);
+
+		mutex_unlock(&b->write_lock);
+
+		btree_nodes[n++] = b;
+		if (n == BTREE_FLUSH_NR)
+			break;
+	}
 	mutex_unlock(&c->bucket_lock);
 
-	if (b) {
+	for (i = 0; i < n; i++) {
+		b = btree_nodes[i];
+		if (!b) {
+			pr_err("BUG: btree_nodes[%d] is NULL", i);
+			continue;
+		}
+
+		/* safe to check without holding b->write_lock */
+		if (!btree_node_journal_flush(b)) {
+			pr_err("BUG: bnode %p: journal_flush bit cleaned", b);
+			continue;
+		}
+
 		mutex_lock(&b->write_lock);
 		if (!btree_current_write(b)->journal) {
 			clear_bit(BTREE_NODE_journal_flush, &b->flags);
 			mutex_unlock(&b->write_lock);
-			/* We raced */
-			goto retry;
+			pr_debug("bnode %p: written by others", b);
+			continue;
+		}
+
+		if (!btree_node_dirty(b)) {
+			clear_bit(BTREE_NODE_journal_flush, &b->flags);
+			mutex_unlock(&b->write_lock);
+			pr_debug("bnode %p: dirty bit cleaned by others", b);
+			continue;
 		}
 
 		__bch_btree_node_write(b, NULL);
 		clear_bit(BTREE_NODE_journal_flush, &b->flags);
 		mutex_unlock(&b->write_lock);
 	}
+
+	spin_lock(&c->journal.flush_write_lock);
+	c->journal.btree_flushing = false;
+	spin_unlock(&c->journal.flush_write_lock);
 }
 
 #define last_seq(j)	((j)->seq - fifo_used(&(j)->pin) + 1)
@@ -881,6 +921,7 @@ int bch_journal_alloc(struct cache_set *c)
 	struct journal *j = &c->journal;
 
 	spin_lock_init(&j->lock);
+	spin_lock_init(&j->flush_write_lock);
 	INIT_DELAYED_WORK(&j->work, journal_write_work);
 
 	c->journal_delay_ms = 100;
diff --git a/drivers/md/bcache/journal.h b/drivers/md/bcache/journal.h
index 66f0facff84b..f2ea34d5f431 100644
--- a/drivers/md/bcache/journal.h
+++ b/drivers/md/bcache/journal.h
@@ -103,6 +103,8 @@ struct journal_write {
 /* 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 journal_device {
 	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)))