linux-kernel - Re: [PATCH 09/12] rdma: use __anon_inode

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Date:   Fri, 8 May 2020 16:52:56 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Christoph Hellwig <hch@....de>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-rdma@...r.kernel.org, kvm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, io-uring@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH 09/12] rdma: use __anon_inode_getfd

On Fri, May 08, 2020 at 05:36:31PM +0200, Christoph Hellwig wrote:
> Use __anon_inode_getfd instead of opencoding the logic using
> get_unused_fd_flags + anon_inode_getfile.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  drivers/infiniband/core/rdma_core.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)

 
> diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c
> index 5128cb16bb485..541e5e06347f6 100644
> --- a/drivers/infiniband/core/rdma_core.c
> +++ b/drivers/infiniband/core/rdma_core.c
> @@ -462,30 +462,21 @@ alloc_begin_fd_uobject(const struct uverbs_api_object *obj,
>  	if (WARN_ON(fd_type->fops->release != &uverbs_uobject_fd_release))
>  		return ERR_PTR(-EINVAL);
>  
> -	new_fd = get_unused_fd_flags(O_CLOEXEC);
> -	if (new_fd < 0)
> -		return ERR_PTR(new_fd);
> -
>  	uobj = alloc_uobj(attrs, obj);
>  	if (IS_ERR(uobj))
> -		goto err_fd;
> +		return uobj;
>  
>  	/* Note that uverbs_uobject_fd_release() is called during abort */
> -	filp = anon_inode_getfile(fd_type->name, fd_type->fops, NULL,
> -				  fd_type->flags);
> -	if (IS_ERR(filp)) {
> -		uobj = ERR_CAST(filp);
> +	new_fd = __anon_inode_getfd(fd_type->name, fd_type->fops, NULL,
> +			fd_type->flags | O_CLOEXEC, &filp);
> +	if (new_fd < 0)
>  		goto err_uobj;

This will conflict with a fix (83a267021221 'RDMA/core: Fix
overwriting of uobj in case of error') that is going to go to -rc
soon.

Also the above misses returning an ERR_PTR if __anon_inode_getfd fails, it
returns a uobj that had been freed.. I suppose it should be something
like

if (new_fd < 0) {
   uverbs_uobject_put(uobj);
   return ERR_PTR(new_fd)
}

?

Jason