When renaming a directory from one parent directory to another,

we need to call ufs_checkpath() to walk from our new location to
the root of the filesystem to ensure that we do not encounter
ourselves along the way. Until now, we accomplished this by reading
the ".." entries of each directory in our path until we reached
the root (or encountered an error). This change tries to avoid the
I/O of reading the ".." entries by first looking them up in the
name cache and only doing the I/O when the name cache lookup fails.

Reviewed by: kib
Tested by:   Peter Holm
MFC after:   4 weeks

3 files changed, 54 insertions, 17 deletions

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index aea71af52107..9eecc0992408 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -1359,6 +1359,28 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 	return (0);
 }
 
+struct vnode *
+vn_dir_dd_ino(struct vnode *vp)
+{
+	struct namecache *ncp;
+	struct vnode *ddvp;
+
+	ASSERT_VOP_LOCKED(vp, "vn_dir_dd_ino");
+	CACHE_RLOCK();
+	TAILQ_FOREACH(ncp, &(vp->v_cache_dst), nc_dst) {
+		if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
+			continue;
+		ddvp = ncp->nc_dvp;
+		VI_LOCK(ddvp);
+		CACHE_RUNLOCK();
+		if (vget(ddvp, LK_INTERLOCK | LK_SHARED | LK_NOWAIT, curthread))
+			return (NULL);
+		return (ddvp);
+	}
+	CACHE_RUNLOCK();
+	return (NULL);
+}
+
 int
 vn_commname(struct vnode *vp, char *buf, u_int buflen)
 {
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index bc16acff9007..42bfb65092a0 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -622,6 +622,8 @@ int	vn_fullpath(struct thread *td, struct vnode *vn,
 	    char **retbuf, char **freebuf);
 int	vn_fullpath_global(struct thread *td, struct vnode *vn,
 	    char **retbuf, char **freebuf);
+struct vnode *
+	vn_dir_dd_ino(struct vnode *vp);
 int	vn_commname(struct vnode *vn, char *buf, u_int buflen);
 int	vn_path_to_global_path(struct thread *td, struct vnode *vp,
 	    char *path, u_int pathlen);
diff --git a/sys/ufs/ufs/ufs_lookup.c b/sys/ufs/ufs/ufs_lookup.c
index 02fda9f18642..70685659633f 100644
--- a/sys/ufs/ufs/ufs_lookup.c
+++ b/sys/ufs/ufs/ufs_lookup.c
@@ -1387,13 +1387,29 @@ ufs_dirempty(ip, parentino, cred)
 }
 
 static int
-ufs_dir_dd_ino(struct vnode *vp, struct ucred *cred, ino_t *dd_ino)
+ufs_dir_dd_ino(struct vnode *vp, struct ucred *cred, ino_t *dd_ino,
+    struct vnode **dd_vp)
 {
 	struct dirtemplate dirbuf;
+	struct vnode *ddvp;
 	int error, namlen;
 
+	ASSERT_VOP_LOCKED(vp, "ufs_dir_dd_ino");
 	if (vp->v_type != VDIR)
 		return (ENOTDIR);
+	/*
+	 * First check to see if we have it in the name cache.
+	 */
+	if ((ddvp = vn_dir_dd_ino(vp)) != NULL) {
+		KASSERT(ddvp->v_mount == vp->v_mount,
+		    ("ufs_dir_dd_ino: Unexpected mount point crossing"));
+		*dd_ino = VTOI(ddvp)->i_number;
+		*dd_vp = ddvp;
+		return (0);
+	}
+	/*
+	 * Have to read the directory.
+	 */
 	error = vn_rdwr(UIO_READ, vp, (caddr_t)&dirbuf,
 	    sizeof (struct dirtemplate), (off_t)0, UIO_SYSSPACE,
 	    IO_NODELOCKED | IO_NOMACCHECK, cred, NOCRED, NULL, NULL);
@@ -1411,6 +1427,7 @@ ufs_dir_dd_ino(struct vnode *vp, struct ucred *cred, ino_t *dd_ino)
 	    dirbuf.dotdot_name[1] != '.')
 		return (ENOTDIR);
 	*dd_ino = dirbuf.dotdot_ino;
+	*dd_vp = NULL;
 	return (0);
 }
 
@@ -1435,7 +1452,7 @@ ufs_checkpath(ino_t source_ino, ino_t parent_ino, struct inode *target, struct u
 	if (target->i_number == ROOTINO)
 		return (0);
 	for (;;) {
-		error = ufs_dir_dd_ino(vp, cred, &dd_ino);
+		error = ufs_dir_dd_ino(vp, cred, &dd_ino, &vp1);
 		if (error != 0)
 			break;
 		if (dd_ino == source_ino) {
@@ -1446,22 +1463,16 @@ ufs_checkpath(ino_t source_ino, ino_t parent_ino, struct inode *target, struct u
 			break;
 		if (dd_ino == parent_ino)
 			break;
-		error = VFS_VGET(mp, dd_ino, LK_SHARED | LK_NOWAIT, &vp1);
-		if (error != 0) {
-			*wait_ino = dd_ino;
-			break;
-		}
-		/* Recheck that ".." still points to vp1 after relock of vp */
-		error = ufs_dir_dd_ino(vp, cred, &dd_ino);
-		if (error != 0) {
-			vput(vp1);
-			break;
-		}
-		/* Redo the check of ".." if directory was reparented */
-		if (dd_ino != VTOI(vp1)->i_number) {
-			vput(vp1);
-			continue;
+		if (vp1 == NULL) {
+			error = VFS_VGET(mp, dd_ino, LK_SHARED | LK_NOWAIT,
+			    &vp1);
+			if (error != 0) {
+				*wait_ino = dd_ino;
+				break;
+			}
 		}
+		KASSERT(dd_ino == VTOI(vp1)->i_number,
+		    ("directory %d reparented\n", VTOI(vp1)->i_number));
 		if (vp != tvp)
 			vput(vp);
 		vp = vp1;
@@ -1469,6 +1480,8 @@ ufs_checkpath(ino_t source_ino, ino_t parent_ino, struct inode *target, struct u
 
 	if (error == ENOTDIR)
 		panic("checkpath: .. not a directory\n");
+	if (vp1 != NULL)
+		vput(vp1);
 	if (vp != tvp)
 		vput(vp);
 	return (error);