Re: [PATCH 3/5] RDMA/srp: Apply the __packed attribute to members instead of structures

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, May 11, 2021 at 08:27:50PM -0700, Bart Van Assche wrote:
> @@ -107,10 +107,10 @@ struct srp_direct_buf {
>   * having the 20-byte structure padded to 24 bytes on 64-bit architectures.
>   */
>  struct srp_indirect_buf {
> -	struct srp_direct_buf	table_desc;
> +	struct srp_direct_buf	table_desc __packed;
>  	__be32			len;
> -	struct srp_direct_buf	desc_list[];
> -} __attribute__((packed));
> +	struct srp_direct_buf	desc_list[] __packed;
> +};
>  
>  /* Immediate data buffer descriptor as defined in SRP2. */
>  struct srp_imm_buf {
> @@ -175,13 +175,13 @@ struct srp_login_rsp {
>  	u8	opcode;
>  	u8	reserved1[3];
>  	__be32	req_lim_delta;
> -	u64	tag;
> +	u64	tag __packed;

What you really want is just something like this:

typedef u64 __attribute__((aligned(4))) compat_u64;

And then use that every place you have the u64 and forget about packed
entirely.

Except for a couple exceptions IBA mads are always aligned to 4 bytes,
only the 64 bit quantities are unaligned.

But really this whole thing should be replaced with the IBA_FIELD
macros like include/rdma/ibta_vol1_c12.h demos.

Then it would be sparse safe and obviously endian correct as well.

I suppose you are respinning this due to the other comments?

Jason