From 3289d5877a321a6e073875da5a1ab374f50fbbff Mon Sep 17 00:00:00 2001
From: Kirk McKusick <mckusick@FreeBSD.org>
Date: Wed, 20 Mar 2013 17:57:00 +0000
Subject: [PATCH] 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
---
 sys/kern/vfs_cache.c     | 22 +++++++++++++++++++
 sys/sys/vnode.h          |  2 ++
 sys/ufs/ufs/ufs_lookup.c | 47 +++++++++++++++++++++++++---------------
 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);