[PATCH 1/2] vfs - rename user_path_umountat() to user_path_mntpointat()

[Ian Kent <raven@themaw.net>]

The function user_path_umountat() not only avoids revalidation but
avoids the managed dentry code as well.

This function has other uses, such as the case where autofs is
reconnecting to a tree of mounts and needs to avoid the managed
dentry call since that would incorrectly cause a callback to the
daemon.

So give the function a more descriptive name.

Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
---
 fs/namei.c            |   34 +++++++++++++++++++---------------
 fs/namespace.c        |    2 +-
 include/linux/namei.h |    2 +-
 3 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index f415c66..24f7562 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2250,7 +2250,7 @@ user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
  *         to the link, and nd->path will *not* be put.
  */
 static int
-umount_lookup_last(struct nameidata *nd, struct path *path)
+mntpoint_lookup_last(struct nameidata *nd, struct path *path)
 {
 	int error = 0;
 	struct dentry *dentry;
@@ -2309,17 +2309,19 @@ error_check:
 }
 
 /**
- * path_umountat - look up a path to be umounted
+ * path_mntpointat - look up a path to a mount point
  * @dfd:	directory file descriptor to start walk from
  * @name:	full pathname to walk
  * @flags:	lookup flags
  * @nd:		pathwalk nameidata
  *
- * Look up the given name, but don't attempt to revalidate the last component.
+ * Look up the given name, but don't attempt to revalidate the last component
+ * or call the managed dentry code.
  * Returns 0 and "path" will be valid on success; Retuns error otherwise.
  */
 static int
-path_umountat(int dfd, const char *name, struct path *path, unsigned int flags)
+path_mntpointat(int dfd, const char *name,
+		struct path *path, unsigned int flags)
 {
 	struct file *base = NULL;
 	struct nameidata nd;
@@ -2343,7 +2345,7 @@ path_umountat(int dfd, const char *name, struct path *path, unsigned int flags)
 		}
 	}
 
-	err = umount_lookup_last(&nd, path);
+	err = mntpoint_lookup_last(&nd, path);
 	while (err > 0) {
 		void *cookie;
 		struct path link = *path;
@@ -2354,7 +2356,7 @@ path_umountat(int dfd, const char *name, struct path *path, unsigned int flags)
 		err = follow_link(&link, &nd, &cookie);
 		if (err)
 			break;
-		err = umount_lookup_last(&nd, path);
+		err = mntpoint_lookup_last(&nd, path);
 		put_link(&nd, &link, cookie);
 	}
 out:
@@ -2368,21 +2370,23 @@ out:
 }
 
 /**
- * user_path_umountat - lookup a path from userland in order to umount it
+ * user_path_mntpointat - lookup a mountpoint path from userland without
+ *      revalidating it or calling the managed dentry code
  * @dfd:	directory file descriptor
  * @name:	pathname from userland
  * @flags:	lookup flags
  * @path:	pointer to container to hold result
  *
- * A umount is a special case for path walking. We're not actually interested
- * in the inode in this situation, and ESTALE errors can be a problem. We
- * simply want track down the dentry and vfsmount attached at the mountpoint
- * and avoid revalidating the last component.
+ * A mount point (when being umounted for example) is a special case for path
+ * walking. We're not actually interested in the inode in this situation, and
+ * ESTALE errors can be a problem. We simply want track down the dentry and
+ * vfsmount attached at the mountpoint and avoid revalidating or calling the
+ * managed dentry code for the last component.
  *
  * Returns 0 and populates "path" on success.
  */
 int
-user_path_umountat(int dfd, const char __user *name, unsigned int flags,
+user_path_mntpointat(int dfd, const char __user *name, unsigned int flags,
 			struct path *path)
 {
 	struct filename *s = getname(name);
@@ -2391,11 +2395,11 @@ user_path_umountat(int dfd, const char __user *name, unsigned int flags,
 	if (IS_ERR(s))
 		return PTR_ERR(s);
 
-	error = path_umountat(dfd, s->name, path, flags | LOOKUP_RCU);
+	error = path_mntpointat(dfd, s->name, path, flags | LOOKUP_RCU);
 	if (unlikely(error == -ECHILD))
-		error = path_umountat(dfd, s->name, path, flags);
+		error = path_mntpointat(dfd, s->name, path, flags);
 	if (unlikely(error == -ESTALE))
-		error = path_umountat(dfd, s->name, path, flags | LOOKUP_REVAL);
+		error = path_mntpointat(dfd, s->name, path, flags|LOOKUP_REVAL);
 
 	if (likely(!error))
 		audit_inode(s, path->dentry, 0);
diff --git a/fs/namespace.c b/fs/namespace.c
index fc2b522..c48ad96 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1321,7 +1321,7 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
 	if (!(flags & UMOUNT_NOFOLLOW))
 		lookup_flags |= LOOKUP_FOLLOW;
 
-	retval = user_path_umountat(AT_FDCWD, name, lookup_flags, &path);
+	retval = user_path_mntpointat(AT_FDCWD, name, lookup_flags, &path);
 	if (retval)
 		goto out;
 	mnt = real_mount(path.mnt);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index cd09751..7908abf 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -58,7 +58,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
 
 extern int user_path_at(int, const char __user *, unsigned, struct path *);
 extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
-extern int user_path_umountat(int, const char __user *, unsigned int, struct path *);
+extern int user_path_mntpointat(int, const char __user *, unsigned int, struct path *);
 
 #define user_path(name, path) user_path_at(AT_FDCWD, name, LOOKUP_FOLLOW, path)
 #define user_lpath(name, path) user_path_at(AT_FDCWD, name, 0, path)