VOP_FSYNC() requires that it's vnode argument be locked, which nfs_link()

wasn't doing.  Rather than just lock and unlock the vnode around the call
to VOP_FSYNC(), implement rwatson's suggestion to lock the file vnode
in kern_link() before calling VOP_LINK(), since the other filesystems
also locked the file vnode right away in their link methods.  Remove the
locking and and unlocking from the leaf filesystem link methods.

Reviewed by:	rwatson, bde  (except for the unionfs_link() changes)

7 files changed, 34 insertions, 44 deletions

diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c
index 92d92ed..9d0d2a1 100644
--- a/sys/fs/unionfs/union_vnops.c
+++ b/sys/fs/unionfs/union_vnops.c
@@ -1224,8 +1224,8 @@ union_remove(ap)
 /*
  *	union_link:
  *
- *	tdvp will be locked on entry, vp will not be locked on entry.
- *	tdvp should remain locked on return and vp should remain unlocked
+ *	tdvp and vp will be locked on entry.
+ *	tdvp and vp should remain locked on return.
  *	on return.
  */
 
@@ -1250,7 +1250,6 @@ union_link(ap)
 		struct union_node *tun = VTOUNION(ap->a_vp);
 
 		if (tun->un_uppervp == NULLVP) {
-			vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY, td);
 #if 0
 			if (dun->un_uppervp == tun->un_dirvp) {
 				if (dun->un_flags & UN_ULOCK) {
@@ -1267,14 +1266,13 @@ union_link(ap)
 				dun->un_flags |= UN_ULOCK;
 			}
 #endif
-			VOP_UNLOCK(ap->a_vp, 0, td);
+			if (error)
+				return (error);
 		}
 		vp = tun->un_uppervp;
+		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
 	}
 
-	if (error)
-		return (error);
-
 	/*
 	 * Make sure upper is locked, then unlock the union directory we were 
 	 * called with to avoid a deadlock while we are calling VOP_LINK on 
@@ -1289,11 +1287,20 @@ union_link(ap)
 	error = VOP_LINK(tdvp, vp, cnp);	/* call link on upper */
 
 	/*
+	 * Unlock tun->un_uppervp if we locked it above.
+	 */
+	if (ap->a_tdvp->v_op == ap->a_vp->v_op)
+		VOP_UNLOCK(vp, 0, td);
+	/*
 	 * We have to unlock tdvp prior to relocking our calling node in
-	 * order to avoid a deadlock.
+	 * order to avoid a deadlock.  We also have to unlock ap->a_vp
+	 * before relocking the directory, but then we have to relock
+	 * ap->a_vp as our caller expects.
 	 */
+	VOP_UNLOCK(ap->a_vp, 0, td);
 	union_unlock_upper(tdvp, td);
 	vn_lock(ap->a_tdvp, LK_EXCLUSIVE | LK_RETRY, td);
+	vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY, td);
 	return (error);
 }
 
diff --git a/sys/gnu/ext2fs/ext2_vnops.c b/sys/gnu/ext2fs/ext2_vnops.c
index dd24a9d..c1fba78 100644
--- a/sys/gnu/ext2fs/ext2_vnops.c
+++ b/sys/gnu/ext2fs/ext2_vnops.c
@@ -827,7 +827,6 @@ ext2_link(ap)
 	struct vnode *vp = ap->a_vp;
 	struct vnode *tdvp = ap->a_tdvp;
 	struct componentname *cnp = ap->a_cnp;
-	struct thread *td = cnp->cn_thread;
 	struct inode *ip;
 	int error;
 
@@ -837,19 +836,16 @@ ext2_link(ap)
 #endif
 	if (tdvp->v_mount != vp->v_mount) {
 		error = EXDEV;
-		goto out2;
-	}
-	if (tdvp != vp && (error = vn_lock(vp, LK_EXCLUSIVE, td))) {
-		goto out2;
+		goto out;
 	}
 	ip = VTOI(vp);
 	if ((nlink_t)ip->i_nlink >= LINK_MAX) {
 		error = EMLINK;
-		goto out1;
+		goto out;
 	}
 	if (ip->i_flags & (IMMUTABLE | APPEND)) {
 		error = EPERM;
-		goto out1;
+		goto out;
 	}
 	ip->i_nlink++;
 	ip->i_flag |= IN_CHANGE;
@@ -860,10 +856,7 @@ ext2_link(ap)
 		ip->i_nlink--;
 		ip->i_flag |= IN_CHANGE;
 	}
-out1:
-	if (tdvp != vp)
-		VOP_UNLOCK(vp, 0, td);
-out2:
+out:
 	return (error);
 }
 
diff --git a/sys/gnu/fs/ext2fs/ext2_vnops.c b/sys/gnu/fs/ext2fs/ext2_vnops.c
index dd24a9d..c1fba78 100644
--- a/sys/gnu/fs/ext2fs/ext2_vnops.c
+++ b/sys/gnu/fs/ext2fs/ext2_vnops.c
@@ -827,7 +827,6 @@ ext2_link(ap)
 	struct vnode *vp = ap->a_vp;
 	struct vnode *tdvp = ap->a_tdvp;
 	struct componentname *cnp = ap->a_cnp;
-	struct thread *td = cnp->cn_thread;
 	struct inode *ip;
 	int error;
 
@@ -837,19 +836,16 @@ ext2_link(ap)
 #endif
 	if (tdvp->v_mount != vp->v_mount) {
 		error = EXDEV;
-		goto out2;
-	}
-	if (tdvp != vp && (error = vn_lock(vp, LK_EXCLUSIVE, td))) {
-		goto out2;
+		goto out;
 	}
 	ip = VTOI(vp);
 	if ((nlink_t)ip->i_nlink >= LINK_MAX) {
 		error = EMLINK;
-		goto out1;
+		goto out;
 	}
 	if (ip->i_flags & (IMMUTABLE | APPEND)) {
 		error = EPERM;
-		goto out1;
+		goto out;
 	}
 	ip->i_nlink++;
 	ip->i_flag |= IN_CHANGE;
@@ -860,10 +856,7 @@ ext2_link(ap)
 		ip->i_nlink--;
 		ip->i_flag |= IN_CHANGE;
 	}
-out1:
-	if (tdvp != vp)
-		VOP_UNLOCK(vp, 0, td);
-out2:
+out:
 	return (error);
 }
 
diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index e1b2d7f..5ad587c 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -1027,10 +1027,12 @@ kern_link(struct thread *td, char *path, char *link, enum uio_seg segflg)
 		if (nd.ni_vp != NULL) {
 			vrele(nd.ni_vp);
 			error = EEXIST;
-		} else {
+		} else if ((error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td))
+		    == 0) {
 			VOP_LEASE(nd.ni_dvp, td, td->td_ucred, LEASE_WRITE);
 			VOP_LEASE(vp, td, td->td_ucred, LEASE_WRITE);
 			error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
+			VOP_UNLOCK(vp, 0, td);
 		}
 		NDFREE(&nd, NDF_ONLY_PNBUF);
 		vput(nd.ni_dvp);
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index e1b2d7f..5ad587c 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -1027,10 +1027,12 @@ kern_link(struct thread *td, char *path, char *link, enum uio_seg segflg)
 		if (nd.ni_vp != NULL) {
 			vrele(nd.ni_vp);
 			error = EEXIST;
-		} else {
+		} else if ((error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td))
+		    == 0) {
 			VOP_LEASE(nd.ni_dvp, td, td->td_ucred, LEASE_WRITE);
 			VOP_LEASE(vp, td, td->td_ucred, LEASE_WRITE);
 			error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
+			VOP_UNLOCK(vp, 0, td);
 		}
 		NDFREE(&nd, NDF_ONLY_PNBUF);
 		vput(nd.ni_dvp);
diff --git a/sys/kern/vnode_if.src b/sys/kern/vnode_if.src
index 3202058..28b5d2e 100644
--- a/sys/kern/vnode_if.src
+++ b/sys/kern/vnode_if.src
@@ -261,7 +261,7 @@ vop_remove {
 
 #
 #% link		tdvp	L L L
-#% link		vp	U U U
+#% link		vp	L L L
 #
 vop_link {
 	IN struct vnode *tdvp;
diff --git a/sys/ufs/ufs/ufs_vnops.c b/sys/ufs/ufs/ufs_vnops.c
index b7d6425..5ec4b6e 100644
--- a/sys/ufs/ufs/ufs_vnops.c
+++ b/sys/ufs/ufs/ufs_vnops.c
@@ -814,7 +814,6 @@ ufs_link(ap)
 	struct vnode *vp = ap->a_vp;
 	struct vnode *tdvp = ap->a_tdvp;
 	struct componentname *cnp = ap->a_cnp;
-	struct thread *td = cnp->cn_thread;
 	struct inode *ip;
 	struct direct newdir;
 	int error;
@@ -825,19 +824,16 @@ ufs_link(ap)
 #endif
 	if (tdvp->v_mount != vp->v_mount) {
 		error = EXDEV;
-		goto out2;
-	}
-	if (tdvp != vp && (error = vn_lock(vp, LK_EXCLUSIVE, td))) {
-		goto out2;
+		goto out;
 	}
 	ip = VTOI(vp);
 	if ((nlink_t)ip->i_nlink >= LINK_MAX) {
 		error = EMLINK;
-		goto out1;
+		goto out;
 	}
 	if (ip->i_flags & (IMMUTABLE | APPEND)) {
 		error = EPERM;
-		goto out1;
+		goto out;
 	}
 	ip->i_effnlink++;
 	ip->i_nlink++;
@@ -859,10 +855,7 @@ ufs_link(ap)
 		if (DOINGSOFTDEP(vp))
 			softdep_change_linkcnt(ip);
 	}
-out1:
-	if (tdvp != vp)
-		VOP_UNLOCK(vp, 0, td);
-out2:
+out:
 	VN_KNOTE(vp, NOTE_LINK);
 	VN_KNOTE(tdvp, NOTE_WRITE);
 	return (error);