Re: [PATCH] ovl: set i_ino to the value of st_ino for NFS export

[Amir Goldstein <amir73il@gmail.com>]

Miklos,

Ping. for rc7?
If you are going to queue this patch for next, please remember to add a
cc: stable tag on it.

Thanks,
Amir.

On Fri, Mar 16, 2018 at 9:39 AM, Amir Goldstein <amir73il@gmail.com> wrote:
> Eddie Horng reported that readdir of an overlayfs directory that
> was exported via NFSv3 returns entries with d_type set to DT_UNKNOWN.
> The reason is that while preparing the response for readdirplus, nfsd
> checks inside encode_entryplus_baggage() that a child dentry's inode
> number matches the value of d_ino returns by overlayfs readdir iterator.
>
> Because the overlayfs inodes use arbitrary inode numbers that are not
> correlated with the values of st_ino/d_ino, NFSv3 falls back to not
> encoding d_type. Although this is an allowed behavior, we can fix it for
> the case of all overlayfs layers on the same underlying filesystem.
>
> When NFS export is enabled and d_ino is consistent with st_ino
> (samefs), set the same value also to i_ino in ovl_fill_inode() for all
> overlayfs inodes, nfsd readdirplus sanity checks will pass.
> ovl_fill_inode() may be called from ovl_new_inode(), before real inode
> was created with ino arg 0. In that case, i_ino will be updated to real
> upper inode i_ino on ovl_inode_init() or ovl_inode_update().
>
> Reported-by: Eddie Horng <eddiehorng.tw@gmail.com>
> Tested-by: Eddie Horng <eddiehorng.tw@gmail.com>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/overlayfs/inode.c | 21 +++++++++++++++++----
>  fs/overlayfs/util.c  |  8 +++++++-
>  2 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 3b1bd469accd..4689716f23d8 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -459,9 +459,20 @@ static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
>  #endif
>  }
>
> -static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
> +static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev,
> +                          unsigned long ino)
>  {
> -       inode->i_ino = get_next_ino();
> +       /*
> +        * When NFS export is enabled and d_ino is consistent with st_ino
> +        * (samefs), set the same value to i_ino, because nfsd readdirplus
> +        * compares d_ino values to i_ino values of child entries. When called
> +        * from ovl_new_inode(), ino arg is 0, so i_ino will be updated to real
> +        * upper inode i_ino on ovl_inode_init() or ovl_inode_update().
> +        */
> +       if (inode->i_sb->s_export_op && ovl_same_sb(inode->i_sb))
> +               inode->i_ino = ino;
> +       else
> +               inode->i_ino = get_next_ino();
>         inode->i_mode = mode;
>         inode->i_flags |= S_NOCMTIME;
>  #ifdef CONFIG_FS_POSIX_ACL
> @@ -597,7 +608,7 @@ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
>
>         inode = new_inode(sb);
>         if (inode)
> -               ovl_fill_inode(inode, mode, rdev);
> +               ovl_fill_inode(inode, mode, rdev, 0);
>
>         return inode;
>  }
> @@ -710,6 +721,7 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
>         struct inode *inode;
>         bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry, index);
>         bool is_dir;
> +       unsigned long ino = 0;
>
>         if (!realinode)
>                 realinode = d_inode(lowerdentry);
> @@ -748,13 +760,14 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
>                 if (!is_dir)
>                         nlink = ovl_get_nlink(lowerdentry, upperdentry, nlink);
>                 set_nlink(inode, nlink);
> +               ino = key->i_ino;
>         } else {
>                 /* Lower hardlink that will be broken on copy up */
>                 inode = new_inode(sb);
>                 if (!inode)
>                         goto out_nomem;
>         }
> -       ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
> +       ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev, ino);
>         ovl_inode_init(inode, upperdentry, lowerdentry);
>
>         if (upperdentry && ovl_is_impuredir(upperdentry))
> diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
> index 930784a26623..493f9b76fbf6 100644
> --- a/fs/overlayfs/util.c
> +++ b/fs/overlayfs/util.c
> @@ -279,12 +279,16 @@ void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
>  void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
>                     struct dentry *lowerdentry)
>  {
> +       struct inode *realinode = d_inode(upperdentry ?: lowerdentry);
> +
>         if (upperdentry)
>                 OVL_I(inode)->__upperdentry = upperdentry;
>         if (lowerdentry)
>                 OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
>
> -       ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
> +       ovl_copyattr(realinode, inode);
> +       if (!inode->i_ino)
> +               inode->i_ino = realinode->i_ino;
>  }
>
>  void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
> @@ -299,6 +303,8 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
>         smp_wmb();
>         OVL_I(inode)->__upperdentry = upperdentry;
>         if (inode_unhashed(inode)) {
> +               if (!inode->i_ino)
> +                       inode->i_ino = upperinode->i_ino;
>                 inode->i_private = upperinode;
>                 __insert_inode_hash(inode, (unsigned long) upperinode);
>         }
> --
> 2.7.4
>