From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Sat, 10 Jun 2023 14:57:23 +0000 (-0400)
Subject: six locks: Disable percpu read lock mode in userspace
X-Git-Tag: io_uring-6.7-2023-11-10~119^2~299
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=aab5e0972a32790c0dbfac64929529820114c674;p=linux-2.6-block.git

six locks: Disable percpu read lock mode in userspace

When running in userspace, we currently don't have a real percpu
implementation available - at least in bcachefs-tools, which is where
this code is currently used in userspace.

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

diff --git a/fs/bcachefs/six.c b/fs/bcachefs/six.c
index 00580f8ff1c5..7ce45aeaee8d 100644
--- a/fs/bcachefs/six.c
+++ b/fs/bcachefs/six.c
@@ -870,6 +870,11 @@ void __six_lock_init(struct six_lock *lock, const char *name,
 	lockdep_init_map(&lock->dep_map, name, key, 0);
 #endif
 
+	/*
+	 * Don't assume that we have real percpu variables available in
+	 * userspace:
+	 */
+#ifdef __KERNEL__
 	if (flags & SIX_LOCK_INIT_PCPU) {
 		/*
 		 * We don't return an error here on memory allocation failure
@@ -880,5 +885,6 @@ void __six_lock_init(struct six_lock *lock, const char *name,
 		 */
 		lock->readers = alloc_percpu(unsigned);
 	}
+#endif
 }
 EXPORT_SYMBOL_GPL(__six_lock_init);