Re: [PATCH v2 2/2] ovl: make consistent use of OVL_FS()

[Amir Goldstein]

On Sat, May 20, 2023 at 9:41 PM Andrea Righi <andrea.righi@xxxxxxxxxxxxx> wrote:
>
> Always use OVL_FS() to retrieve the corresponding struct ovl_fs from a
> struct super_block.
>
> Moreover, make sure that it is exclusively used with an overlayfs
> superblock when CONFIG_OVERLAY_FS_DEBUG is enabled (otherwise trigger a
> WARN_ON_ONCE).

Seems that you do not mind learning how we usually do things...
so "Moreover", "Also" is usually an indication that this change needs to be
in a separate patch.
I think this is one of those cases.

>
> Signed-off-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx>
> ---
>  fs/overlayfs/copy_up.c   |  2 +-
>  fs/overlayfs/export.c    | 10 +++++-----
>  fs/overlayfs/inode.c     |  8 ++++----
>  fs/overlayfs/namei.c     |  2 +-
>  fs/overlayfs/ovl_entry.h | 16 ++++++++++++++++
>  fs/overlayfs/super.c     | 12 ++++++------
>  fs/overlayfs/util.c      | 18 +++++++++---------
>  7 files changed, 42 insertions(+), 26 deletions(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index f658cc8ea492..60aa615820e7 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -905,7 +905,7 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
>  static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
>                                   int flags)
>  {
> -       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
>
>         if (!ofs->config.metacopy)
>                 return false;
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index defd4e231ad2..f5f0ef8e3ce8 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -182,7 +182,7 @@ static int ovl_connect_layer(struct dentry *dentry)
>   */
>  static int ovl_check_encode_origin(struct dentry *dentry)
>  {
> -       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
>
>         /* Upper file handle for pure upper */
>         if (!ovl_dentry_lower(dentry))
> @@ -434,7 +434,7 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
>                                             struct dentry *real,
>                                             const struct ovl_layer *layer)
>  {
> -       struct ovl_fs *ofs = sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(sb);
>         struct dentry *index = NULL;
>         struct dentry *this = NULL;
>         struct inode *inode;
> @@ -655,7 +655,7 @@ static struct dentry *ovl_get_dentry(struct super_block *sb,
>                                      struct ovl_path *lowerpath,
>                                      struct dentry *index)
>  {
> -       struct ovl_fs *ofs = sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(sb);
>         const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
>         struct dentry *real = upper ?: (index ?: lowerpath->dentry);
>
> @@ -680,7 +680,7 @@ static struct dentry *ovl_get_dentry(struct super_block *sb,
>  static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
>                                         struct ovl_fh *fh)
>  {
> -       struct ovl_fs *ofs = sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(sb);
>         struct dentry *dentry;
>         struct dentry *upper;
>
> @@ -700,7 +700,7 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
>  static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
>                                         struct ovl_fh *fh)
>  {
> -       struct ovl_fs *ofs = sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(sb);
>         struct ovl_path origin = { };
>         struct ovl_path *stack = &origin;
>         struct dentry *dentry = NULL;
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 541cf3717fc2..c27823f6e7aa 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -334,7 +334,7 @@ static const char *ovl_get_link(struct dentry *dentry,
>
>  bool ovl_is_private_xattr(struct super_block *sb, const char *name)
>  {
> -       struct ovl_fs *ofs = sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(sb);
>
>         if (ofs->config.userxattr)
>                 return strncmp(name, OVL_XATTR_USER_PREFIX,
> @@ -689,7 +689,7 @@ int ovl_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
>  int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
>  {
>         if (flags & S_ATIME) {
> -               struct ovl_fs *ofs = inode->i_sb->s_fs_info;
> +               struct ovl_fs *ofs = OVL_FS(inode->i_sb);
>                 struct path upperpath = {
>                         .mnt = ovl_upper_mnt(ofs),
>                         .dentry = ovl_upperdentry_dereference(OVL_I(inode)),
> @@ -952,7 +952,7 @@ static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
>
>  static void ovl_next_ino(struct inode *inode)
>  {
> -       struct ovl_fs *ofs = inode->i_sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(inode->i_sb);
>
>         inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
>         if (unlikely(!inode->i_ino))
> @@ -1284,7 +1284,7 @@ struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
>  static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
>                              struct dentry *lower, bool index)
>  {
> -       struct ovl_fs *ofs = sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(sb);
>
>         /* No, if pure upper */
>         if (!lower)
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index cfb3420b7df0..d0f196b85541 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -832,7 +832,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
>  {
>         struct ovl_entry *oe;
>         const struct cred *old_cred;
> -       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
> +       struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
>         struct ovl_entry *poe = dentry->d_parent->d_fsdata;
>         struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
>         struct ovl_path *stack = NULL, *origin_path = NULL;
> diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
> index fd11fe6d6d45..0b93b1d9ad79 100644
> --- a/fs/overlayfs/ovl_entry.h
> +++ b/fs/overlayfs/ovl_entry.h
> @@ -95,8 +95,24 @@ static inline struct mnt_idmap *ovl_upper_mnt_idmap(struct ovl_fs *ofs)
>         return mnt_idmap(ovl_upper_mnt(ofs));
>  }
>
> +extern struct file_system_type ovl_fs_type;
> +
> +#ifdef CONFIG_OVERLAY_FS_DEBUG
> +static inline bool is_ovl_fs_sb(struct super_block *sb)
> +{
> +       return sb->s_type == &ovl_fs_type;
> +}
> +#else
> +static inline bool is_ovl_fs_sb(struct super_block *sb)
> +{
> +       return true;
> +}
> +#endif
> +
>  static inline struct ovl_fs *OVL_FS(struct super_block *sb)
>  {
> +       WARN_ON_ONCE(!is_ovl_fs_sb(sb));
> +
>         return (struct ovl_fs *)sb->s_fs_info;
>  }
>

IMO, is_ovl_fs_sb() is useful and no reason to hide it under
CONFIG_OVERLAY_FS_DEBUG.
IMO, only the fortification of OVL_FS() needs to be hidden inside
CONFIG_OVERLAY_FS_DEBUG.

With those minor comments fixed you may add:

Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>

Thanks,
Amir.