> On Dec 7, 2022, at 3:43 AM, Richard Weinberger <richard@xxxxxx> wrote:
>
> 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@xxxxxx>
> ---
> fs/namei.c | 6 +++---
> fs/nfsd/vfs.c | 6 +++++-
> include/linux/namei.h | 2 +-
> 3 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 578c2110df02..a6bb6863bf0c 100644
> --- 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 157f0df0e93a..ced04fc2b947 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -63,9 +63,13 @@ 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 00fee52df842..6f96db73a70a 100644
> --- 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 *, unsigned int flags);
> extern int follow_up(struct path *);
>
> extern struct dentry *lock_rename(struct dentry *, struct dentry *);
> --
> 2.26.2
>
I plan to take this through the nfsd tree, thus this one needs
an Ack from the VFS maintainer(s).
--
Chuck Lever
