Re: [PATCH v2 04/17] IB/core: Add umem function to read data from user-space

[Yann Droneaud <ydroneaud-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org>]

Hi,

Le mardi 11 novembre 2014 à 18:36 +0200, Haggai Eran a écrit :
> In some drivers there's a need to read data from a user space area that
> was pinned using ib_umem, when running from a different process context.
> 
> The ib_umem_copy_from function allows reading data from the physical pages
> pinned in the ib_umem struct.
> 
> Signed-off-by: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> ---
>  drivers/infiniband/core/umem.c | 26 ++++++++++++++++++++++++++
>  include/rdma/ib_umem.h         |  2 ++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
> index e0f883292374..77bec75963e7 100644
> --- a/drivers/infiniband/core/umem.c
> +++ b/drivers/infiniband/core/umem.c
> @@ -292,3 +292,29 @@ int ib_umem_page_count(struct ib_umem *umem)
>  	return n;
>  }
>  EXPORT_SYMBOL(ib_umem_page_count);
> +
> +/*
> + * Copy from the given ib_umem's pages to the given buffer.
> + *
> + * umem - the umem to copy from
> + * offset - offset to start copying from
> + * dst - destination buffer
> + * length - buffer length
> + *
> + * Returns the number of copied bytes, or an error code.
> + */
> +int ib_umem_copy_from(struct ib_umem *umem, size_t offset, void *dst,
> +		      size_t length)

I would prefer the arguments in the same order as ib_copy_from_udata()

int ib_umem_copy_from(void *dst,
                      struct ib_umem *umem, size_t umem_offset,
                      size_t length);
 

> +{
> +	size_t end = offset + length;
> +
> +	if (offset > umem->length || end > umem->length || end < offset) {
> +		pr_err("ib_umem_copy_from not in range. offset: %zd umem length: %zd end: %zd\n",
> +		       offset, umem->length, end);
> +		return -EINVAL;
> +	}
> +
> +	return sg_pcopy_to_buffer(umem->sg_head.sgl, umem->nmap, dst, length,
> +			offset + ib_umem_offset(umem));
> +}
> +EXPORT_SYMBOL(ib_umem_copy_from);

As the function return a "int", no more than INT_MAX bytes (likely 2^31
- 1) can be copied. Perhaps changing the return type to to ssize_t would
be better (and a check to enfore ssize_t maximum value). Or change the
function could return 0 in case of success or a error code, just like
ib_copy_from_udata().

> diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h
> index 7ed6d4ff58dc..ee897724cbf8 100644
> --- a/include/rdma/ib_umem.h
> +++ b/include/rdma/ib_umem.h
> @@ -84,6 +84,8 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
>  			    size_t size, int access, int dmasync);
>  void ib_umem_release(struct ib_umem *umem);
>  int ib_umem_page_count(struct ib_umem *umem);
> +int ib_umem_copy_from(struct ib_umem *umem, size_t start, void *dst,
> +		      size_t length);
>  
>  #else /* CONFIG_INFINIBAND_USER_MEM */
>  


--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html