Quiet a WITNESS warning with the dirhash sx locks by setting the DUPOK

flag.  Specifically, if two threads race to create a dirhash for a
directory, then one might already have created a private dirhash
structure (and locked it) when it realizes the directory now has a
structure and tries to lock that one.

1 files changed, 10 insertions, 1 deletions

diff --git a/sys/ufs/ufs/ufs_dirhash.c b/sys/ufs/ufs/ufs_dirhash.c
index cabb09c..05bf840 100644
--- a/sys/ufs/ufs/ufs_dirhash.c
+++ b/sys/ufs/ufs/ufs_dirhash.c
@@ -181,7 +181,16 @@ ufsdirhash_create(struct inode *ip)
 			if (ndh == NULL)
 				return (NULL);
 			refcount_init(&ndh->dh_refcount, 1);
-			sx_init(&ndh->dh_lock, "dirhash");
+
+			/*
+			 * The DUPOK is to prevent warnings from the
+			 * sx_slock() a few lines down which is safe
+			 * since the duplicate lock in that case is
+			 * the one for this dirhash we are creating
+			 * now which has no external references until
+			 * after this function returns.
+			 */
+			sx_init_flags(&ndh->dh_lock, "dirhash", SX_DUPOK);
 			sx_xlock(&ndh->dh_lock);
 		}
 		/*