Commit 62448afe authored by Kent Overstreet's avatar Kent Overstreet Committed by Kent Overstreet
Browse files

bcachefs: Fix bch2_btree_node_upgrade() 



Previously, if we were trying to upgrade from a read to an intent lock
but we held an additional read lock via another btree_path,
bch2_btree_node_upgrade() would always fail, in six_lock_tryupgrade().

This patch factors out the code that __bch2_btree_node_lock_write() uses
to temporarily drop extra read locks, so that six_lock_tryupgrade() can
succeed.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@gmail.com>
parent 845cffed

fs/bcachefs/btree_locking.c

+18 −4
Original line number Diff line number Diff line
@@ -230,6 +230,7 @@ bool bch2_btree_node_upgrade(struct btree_trans *trans, 
			     struct btree_path *path, unsigned level)

{

	struct btree *b = path->l[level].b;

	struct six_lock_count count = bch2_btree_node_lock_counts(trans, path, &b->c, level);



	if (!is_btree_node(path, level))

		return false;
@@ -253,11 +254,24 @@ bool bch2_btree_node_upgrade(struct btree_trans *trans, 
	if (race_fault())

		return false;



	if (btree_node_locked(path, level)

	    ? six_lock_tryupgrade(&b->c.lock)

	    : six_relock_type(&b->c.lock, SIX_LOCK_intent, path->l[level].lock_seq))

	if (btree_node_locked(path, level)) {

		bool ret;



		six_lock_readers_add(&b->c.lock, -count.n[SIX_LOCK_read]);

		ret = six_lock_tryupgrade(&b->c.lock);

		six_lock_readers_add(&b->c.lock, count.n[SIX_LOCK_read]);



		if (ret)

			goto success;

	} else {

		if (six_relock_type(&b->c.lock, SIX_LOCK_intent, path->l[level].lock_seq))

			goto success;

	}



	/*

	 * Do we already have an intent lock via another path? If so, just bump

	 * lock count:

	 */

	if (btree_node_lock_seq_matches(path, b, level) &&

	    btree_node_lock_increment(trans, &b->c, level, BTREE_NODE_INTENT_LOCKED)) {

		btree_node_unlock(trans, path, level);