Re: [PATCH] ceph: fail the open_by_handle_at() if the dentry is being unlinked

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2022-08-04 at 16:06 +0800, xiubli@redhat.com wrote:
> From: Xiubo Li <xiubli@redhat.com>
> 
> When unlinking a file the kclient will send a unlink request to MDS
> by holding the dentry reference, and then the MDS will return 2 replies,
> which are unsafe reply and a deferred safe reply.
> 
> After the unsafe reply received the kernel will return and succeed
> the unlink request to user space apps.
> 
> Only when the safe reply received the dentry's reference will be
> released. Or the dentry will only be unhashed from dcache. But when
> the open_by_handle_at() begins to open the unlinked files it will
> succeed.
> 
> URL: https://tracker.ceph.com/issues/56524
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>  fs/ceph/export.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> index 0ebf2bd93055..7d2ae977b8c9 100644
> --- a/fs/ceph/export.c
> +++ b/fs/ceph/export.c
> @@ -182,6 +182,7 @@ struct inode *ceph_lookup_inode(struct super_block *sb, u64 ino)
>  static struct dentry *__fh_to_dentry(struct super_block *sb, u64 ino)
>  {
>  	struct inode *inode = __lookup_inode(sb, ino);
> +	struct dentry *dentry;
>  	int err;
>  
>  	if (IS_ERR(inode))
> @@ -197,7 +198,15 @@ static struct dentry *__fh_to_dentry(struct super_block *sb, u64 ino)
>  		iput(inode);
>  		return ERR_PTR(-ESTALE);
>  	}
> -	return d_obtain_alias(inode);
> +
> +	/* -ESTALE if the dentry is unhashed, which should being released */
> +	dentry = d_obtain_alias(inode);
> +	if (d_unhashed(dentry)) {
> +		dput(dentry);
> +		return ERR_PTR(-ESTALE);
> +	}
> +
> +	return dentry;
>  }
>  
>  static struct dentry *__snapfh_to_dentry(struct super_block *sb,

Reviewed-by: Jeff Layton <jlayton@kernel.org>