From 9904f3d96892171a40469b83d51181e130737660 Mon Sep 17 00:00:00 2001
From: mckusick <mckusick@FreeBSD.org>
Date: Wed, 20 Mar 2013 17:57:00 +0000
Subject: 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 aea71af..9eecc09 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 bc16acf..42bfb65 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 02fda9f..7068565 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);
-- 
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