From: Kent Overstreet <kent.overstreet@gmail.com>
Date: Thu, 15 Apr 2021 22:31:58 +0000 (-0400)
Subject: bcachefs: Fix an RCU splat
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3e07a7300f0684f7c77485e65a1ae97c7ab2514f;p=linux.git

bcachefs: Fix an RCU splat

Writepoints are never deallocated so the rcu_read_lock() isn't really
needed, but we are doing lockless list traversal.

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

diff --git a/fs/bcachefs/alloc_foreground.c b/fs/bcachefs/alloc_foreground.c
index 4834ac798b9e9..56b114888e49a 100644
--- a/fs/bcachefs/alloc_foreground.c
+++ b/fs/bcachefs/alloc_foreground.c
@@ -683,11 +683,14 @@ static struct write_point *__writepoint_find(struct hlist_head *head,
 {
 	struct write_point *wp;
 
+	rcu_read_lock();
 	hlist_for_each_entry_rcu(wp, head, node)
 		if (wp->write_point == write_point)
-			return wp;
-
-	return NULL;
+			goto out;
+	wp = NULL;
+out:
+	rcu_read_unlock();
+	return wp;
 }
 
 static inline bool too_many_writepoints(struct bch_fs *c, unsigned factor)