Simply shared vnode locking and extend it to also include fsync.

Also, in vop_write, no longer assert for exclusive locks on the
vnode.

Reviewed by:	jhb, kmacy, jeffr

1 files changed, 8 insertions, 2 deletions

diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 72a53f8f7058..1cc6d2d31264 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -3476,7 +3476,7 @@ fsync(td, uap)
 	struct mount *mp;
 	struct file *fp;
 	int vfslocked;
-	int error;
+	int error, lock_flags;
 
 	AUDIT_ARG(fd, uap->fd);
 	if ((error = getvnode(td->td_proc->p_fd, uap->fd, &fp)) != 0)
@@ -3485,7 +3485,13 @@ fsync(td, uap)
 	vfslocked = VFS_LOCK_GIANT(vp->v_mount);
 	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
 		goto drop;
-	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+	if (MNT_SHARED_WRITES(mp) ||
+	    ((mp == NULL) && MNT_SHARED_WRITES(vp->v_mount))) {
+		lock_flags = LK_SHARED;
+	} else {
+		lock_flags = LK_EXCLUSIVE;
+	}
+	vn_lock(vp, lock_flags | LK_RETRY);
 	AUDIT_ARG(vnode, vp, ARG_VNODE1);
 	if (vp->v_object != NULL) {
 		VM_OBJECT_LOCK(vp->v_object);