diff --git a/sys/fs/msdosfs/msdosfs_vfsops.c b/sys/fs/msdosfs/msdosfs_vfsops.c
index 213dd00..d4abf8b 100644
--- a/sys/fs/msdosfs/msdosfs_vfsops.c
+++ b/sys/fs/msdosfs/msdosfs_vfsops.c
@@ -471,7 +471,7 @@ mountmsdosfs(struct vnode *devvp, struct mount *mp)
 	pmp->pm_cp = cp;
 	pmp->pm_bo = bo;
 
-	lockinit(&pmp->pm_fatlock, 0, msdosfs_lock_msg, 0, 0);
+	sx_init(&pmp->pm_fatlock, msdosfs_lock_msg);
 
 	/*
 	 * Initialize ownerships and permissions, since nothing else will
@@ -777,7 +777,7 @@ error_exit:
 		PICKUP_GIANT();
 	}
 	if (pmp) {
-		lockdestroy(&pmp->pm_fatlock);
+		sx_destroy(&pmp->pm_fatlock);
 		if (pmp->pm_inusemap)
 			free(pmp->pm_inusemap, M_MSDOSFSFAT);
 		free(pmp, M_MSDOSFSMNT);
@@ -854,7 +854,7 @@ msdosfs_unmount(struct mount *mp, int mntflags)
 	free(pmp->pm_inusemap, M_MSDOSFSFAT);
 	if (pmp->pm_flags & MSDOSFS_LARGEFS)
 		msdosfs_fileno_free(mp);
-	lockdestroy(&pmp->pm_fatlock);
+	sx_destroy(&pmp->pm_fatlock);
 	free(pmp, M_MSDOSFSMNT);
 	mp->mnt_data = NULL;
 	MNT_ILOCK(mp);
diff --git a/sys/fs/msdosfs/msdosfsmount.h b/sys/fs/msdosfs/msdosfsmount.h
index 10ed95b..1dcffbd 100644
--- a/sys/fs/msdosfs/msdosfsmount.h
+++ b/sys/fs/msdosfs/msdosfsmount.h
@@ -55,7 +55,7 @@
 
 #include <sys/types.h>
 #include <sys/lock.h>
-#include <sys/lockmgr.h>
+#include <sys/sx.h>
 #include <sys/tree.h>
 
 #ifdef MALLOC_DECLARE
@@ -111,7 +111,7 @@ struct msdosfsmount {
 	u_int32_t pm_nfileno;	/* next 32-bit fileno */
 	RB_HEAD(msdosfs_filenotree, msdosfs_fileno)
 	    pm_filenos; /* 64<->32-bit fileno mapping */
-	struct lock pm_fatlock;	/* lockmgr protecting allocations and rb tree */
+	struct sx pm_fatlock;	/* sx protecting allocations and rb tree */
 };
 
 /*
@@ -220,12 +220,9 @@ void msdosfs_fileno_init(struct mount *);
 void msdosfs_fileno_free(struct mount *);
 uint32_t msdosfs_fileno_map(struct mount *, uint64_t);
 
-#define	MSDOSFS_LOCK_MP(pmp) \
-	lockmgr(&(pmp)->pm_fatlock, LK_EXCLUSIVE, NULL)
-#define	MSDOSFS_UNLOCK_MP(pmp) \
-	lockmgr(&(pmp)->pm_fatlock, LK_RELEASE, NULL)
-#define	MSDOSFS_ASSERT_MP_LOCKED(pmp) \
-	lockmgr_assert(&(pmp)->pm_fatlock, KA_XLOCKED)
+#define	MSDOSFS_LOCK_MP(pmp) sx_xlock(&(pmp)->pm_fatlock)
+#define	MSDOSFS_UNLOCK_MP(pmp) sx_xunlock(&(pmp)->pm_fatlock)
+#define	MSDOSFS_ASSERT_MP_LOCKED(pmp) sx_assert(&(pmp)->pm_fatlock, SA_XLOCKED)
 
 #endif /* _KERNEL */