fs: namei: Allow follow_down() to uncover auto mounts

This function is only used by NFSD to cross mount points.
If a mount point is of type auto mount, follow_down() will
not uncover it. Add LOOKUP_AUTOMOUNT to the lookup flags
to have ->d_automount() called when NFSD walks down the
mount tree.

Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Ian Kent <raven@themaw.net>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/namei.c b/fs/namei.c
index 309ae6fc8c993b8057a560da88de4971fa004127..c06f4706606302c319a736e29e50fe30a35a7d79 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1458,11 +1458,11 @@ EXPORT_SYMBOL(follow_down_one);
  * point, the filesystem owning that dentry may be queried as to whether the
  * caller is permitted to proceed or not.
  */
-int follow_down(struct path *path)
+int follow_down(struct path *path, unsigned int flags)
 {
        struct vfsmount *mnt = path->mnt;
        bool jumped;
-       int ret = traverse_mounts(path, &jumped, NULL, 0);
+       int ret = traverse_mounts(path, &jumped, NULL, flags);
 
        if (path->mnt != mnt)
                mntput(mnt);
@@ -2864,7 +2864,7 @@ int path_pts(struct path *path)
 
        path->dentry = child;
        dput(parent);
-       follow_down(path);
+       follow_down(path, 0);
        return 0;
 }
 #endif

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 780856561bbba7d56cf2c15066433d94d5dfa4a4..21d5209f6e041b7c1a53c776c7662c853bb54396 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -126,9 +126,13 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
        struct dentry *dentry = *dpp;
        struct path path = {.mnt = mntget(exp->ex_path.mnt),
                            .dentry = dget(dentry)};
+       unsigned int follow_flags = 0;
        int err = 0;
 
-       err = follow_down(&path);
+       if (exp->ex_flags & NFSEXP_CROSSMOUNT)
+               follow_flags = LOOKUP_AUTOMOUNT;
+
+       err = follow_down(&path, follow_flags);
        if (err < 0)
                goto out;
        if (path.mnt == exp->ex_path.mnt && path.dentry == dentry &&

diff --git a/include/linux/namei.h b/include/linux/namei.h
index 00fee52df84234cfcf7a0bf8bbe327df547b07c4..c82e2ac65846401251916c5209e25f56919897e2 100644 (file)
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -77,7 +77,7 @@ struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
                                            struct dentry *base, int len);
 
 extern int follow_down_one(struct path *);
-extern int follow_down(struct path *);
+extern int follow_down(struct path *path, unsigned int flags);
 extern int follow_up(struct path *);
 
 extern struct dentry *lock_rename(struct dentry *, struct dentry *);