From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Fri, 2 Sep 2022 02:05:16 +0000 (-0400)
Subject: bcachefs: Fix six_lock_readers_add()
X-Git-Tag: v6.7-rc1~201^2~798
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6b81f194f345d15dd15601ee7b604a0640445895;p=thirdparty%2Fkernel%2Flinux.git

bcachefs: Fix six_lock_readers_add()

Have to be careful with bit fields - when subtracting, this was
overflowing into the write_locking bit.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---

diff --git a/fs/bcachefs/btree_locking.c b/fs/bcachefs/btree_locking.c
index 24d0ea9033802..158cb7ac64f28 100644
--- a/fs/bcachefs/btree_locking.c
+++ b/fs/bcachefs/btree_locking.c
@@ -10,10 +10,12 @@ struct lock_class_key bch2_btree_node_lock_key;
 
 static inline void six_lock_readers_add(struct six_lock *lock, int nr)
 {
-	if (!lock->readers)
+	if (lock->readers)
+		this_cpu_add(*lock->readers, nr);
+	else if (nr > 0)
 		atomic64_add(__SIX_VAL(read_lock, nr), &lock->state.counter);
 	else
-		this_cpu_add(*lock->readers, nr);
+		atomic64_sub(__SIX_VAL(read_lock, -nr), &lock->state.counter);
 }
 
 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *trans,