Move the head of byte-level advisory lock list from the

filesystem-specific vnode data to the struct vnode. Provide the
default implementation for the vop_advlock and vop_advlockasync.
Purge the locks on the vnode reclaim by using the lf_purgelocks().
The default implementation is augmented for the nfs and smbfs.
In the nfs_advlock, push the Giant inside the nfs_dolock.

Before the change, the vop_advlock and vop_advlockasync have taken the
unlocked vnode and dereferenced the fs-private inode data, racing with
with the vnode reclamation due to forced unmount. Now, the vop_getattr
under the shared vnode lock is used to obtain the inode size, and
later, in the lf_advlockasync, after locking the vnode interlock, the
VI_DOOMED flag is checked to prevent an operation on the doomed vnode.

The implementation of the lf_purgelocks() is submitted by dfr.

Reported by:	kris
Tested by:	kris, pho
Discussed with:	jeff, dfr
MFC after:	2 weeks

1 files changed, 29 insertions, 11 deletions

diff --git a/sys/nfs4client/nfs4_vnops.c b/sys/nfs4client/nfs4_vnops.c
index 633f1c3..276cb1a 100644
--- a/sys/nfs4client/nfs4_vnops.c
+++ b/sys/nfs4client/nfs4_vnops.c
@@ -2763,14 +2763,22 @@ done:
 static int
 nfs4_advlock(struct vop_advlock_args *ap)
 {
-	return (EPERM);
+	struct vnode *vp = ap->a_vp;
+	u_quad_t size;
+	int error;
 
-	if ((VFSTONFS(ap->a_vp->v_mount)->nm_flag & NFSMNT_NOLOCKD) != 0) {
-		struct nfsnode *np = VTONFS(ap->a_vp);
+	return (EPERM);
 
-		return (lf_advlock(ap, &(np->n_lockf), np->n_size));
-	}
-	return (nfs_dolock(ap));
+	error = vn_lock(vp, LK_SHARED);
+	if (error)
+		return (error);
+	if ((VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NOLOCKD) != 0) {
+		size = VTONFS(vp)->n_size;
+		VOP_UNLOCK(vp, 0);
+		error = lf_advlock(ap, &(vp->v_lockf), size);
+	} else
+		error = nfs_dolock(ap);
+	return (error);
 }
 
 /*
@@ -2779,14 +2787,24 @@ nfs4_advlock(struct vop_advlock_args *ap)
 static int
 nfs4_advlockasync(struct vop_advlockasync_args *ap)
 {
-	return (EPERM);
+	struct vnode *vp = ap->a_vp;
+	u_quad_t size;
+	int error;
 
-	if ((VFSTONFS(ap->a_vp->v_mount)->nm_flag & NFSMNT_NOLOCKD) != 0) {
-		struct nfsnode *np = VTONFS(ap->a_vp);
+	return (EPERM);
 
-		return (lf_advlockasync(ap, &(np->n_lockf), np->n_size));
+	error = vn_lock(vp, LK_SHARED);
+	if (error)
+		return (error);
+	if ((VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NOLOCKD) != 0) {
+		size = VTONFS(vp)->n_size;
+		VOP_UNLOCK(vp, 0);
+		error = lf_advlockasync(ap, &(vp->v_lockf), size);
+	} else {
+		VOP_UNLOCK(vp, 0);
+		error = EOPNOTSUPP;
 	}
-	return (EOPNOTSUPP);
+	return (error);
 }
 
 /*