On Tue 01-09-26 14:14:27, Christian Brauner wrote:
> struct mnt_idmap is immutable once alloc_mnt_idmap() has set it up. The
> only thing that changes afterwards is the reference count. Model
> mnt_idmap_{get,put}() after struct cred's reference count handling and
> take a const pointer.
>
> This model is forced upon us because ceph stores the idmapping in mds
> requests and need to be able to take and put references.
>
> mnt_idmap_get() keeps returning a non-const pointer for now because
> struct vfsmount still stores a non-const pointer. We can only change
> that at the end of the series once every user of mnt_idmap() has been
> ported.
>
> Signed-off-by: Christian Brauner (Amutable) <[email protected]>
Yeah, this is a bit ugly but it's convenient :) and in the great scheme of
things I think it's a win. Feel free to add:
Reviewed-by: Jan Kara <[email protected]>
Honza
> ---
> fs/internal.h | 4 ++--
> fs/mnt_idmapping.c | 16 ++++++++++------
> include/linux/mnt_idmapping.h | 4 ++--
> 3 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/fs/internal.h b/fs/internal.h
> index c658c8a5ebd5..581aaa2d6510 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -327,8 +327,8 @@ ssize_t __kernel_write_iter(struct file *file, struct
> iov_iter *from, loff_t *po
> * fs/attr.c
> */
> struct mnt_idmap *alloc_mnt_idmap(struct user_namespace *mnt_userns);
> -struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap);
> -void mnt_idmap_put(struct mnt_idmap *idmap);
> +struct mnt_idmap *mnt_idmap_get(const struct mnt_idmap *idmap);
> +void mnt_idmap_put(const struct mnt_idmap *idmap);
> struct stashed_operations {
> struct dentry *(*stash_dentry)(struct dentry **stashed,
> struct dentry *dentry);
> diff --git a/fs/mnt_idmapping.c b/fs/mnt_idmapping.c
> index cb61fbdb52e9..cc6c5f1cfba8 100644
> --- a/fs/mnt_idmapping.c
> +++ b/fs/mnt_idmapping.c
> @@ -312,12 +312,14 @@ struct mnt_idmap *alloc_mnt_idmap(struct user_namespace
> *mnt_userns)
> *
> * Return: @idmap with reference count bumped if @not_mnt_idmap isn't passed.
> */
> -struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap)
> +struct mnt_idmap *mnt_idmap_get(const struct mnt_idmap *idmap)
> {
> + struct mnt_idmap *nonconst_idmap = (struct mnt_idmap *)idmap;
> +
> if (idmap != &nop_mnt_idmap && idmap != &invalid_mnt_idmap)
> - refcount_inc(&idmap->count);
> + refcount_inc(&nonconst_idmap->count);
>
> - return idmap;
> + return nonconst_idmap;
> }
> EXPORT_SYMBOL_GPL(mnt_idmap_get);
>
> @@ -328,11 +330,13 @@ EXPORT_SYMBOL_GPL(mnt_idmap_get);
> * If this is a non-initial idmapping, put the reference count when a mount
> is
> * released and free it if we're the last user.
> */
> -void mnt_idmap_put(struct mnt_idmap *idmap)
> +void mnt_idmap_put(const struct mnt_idmap *idmap)
> {
> + struct mnt_idmap *nonconst_idmap = (struct mnt_idmap *)idmap;
> +
> if (idmap != &nop_mnt_idmap && idmap != &invalid_mnt_idmap &&
> - refcount_dec_and_test(&idmap->count))
> - free_mnt_idmap(idmap);
> + refcount_dec_and_test(&nonconst_idmap->count))
> + free_mnt_idmap(nonconst_idmap);
> }
> EXPORT_SYMBOL_GPL(mnt_idmap_put);
>
> diff --git a/include/linux/mnt_idmapping.h b/include/linux/mnt_idmapping.h
> index e71a6070a8f8..e5bee8b41094 100644
> --- a/include/linux/mnt_idmapping.h
> +++ b/include/linux/mnt_idmapping.h
> @@ -121,8 +121,8 @@ static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t
> kgid)
>
> int vfsgid_in_group_p(vfsgid_t vfsgid);
>
> -struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap);
> -void mnt_idmap_put(struct mnt_idmap *idmap);
> +struct mnt_idmap *mnt_idmap_get(const struct mnt_idmap *idmap);
> +void mnt_idmap_put(const struct mnt_idmap *idmap);
>
> vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
> struct user_namespace *fs_userns, kuid_t kuid);
>
> --
> 2.53.0
>
--
Jan Kara <[email protected]>
SUSE Labs, CR
