[v4,1/2] RDS: memory allocated must be align to 8

Fix issue in 'rds_ib_cong_recv' when accessing unaligned memory
allocated by 'rds_page_remainder_alloc' using uint64_t pointer.

Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
---
 net/rds/page.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

On 4/7/2016 4:57 AM, Shamir Rabinovitch wrote:
> Fix issue in 'rds_ib_cong_recv' when accessing unaligned memory
> allocated by 'rds_page_remainder_alloc' using uint64_t pointer.
>
Sorry I still didn't follow this change still. What exactly is the
problem.

> Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
> ---
>   net/rds/page.c |    4 ++--
>   1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/rds/page.c b/net/rds/page.c
> index 616f21f..e2b5a58 100644
> --- a/net/rds/page.c
> +++ b/net/rds/page.c
> @@ -135,8 +135,8 @@ int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
>   			if (rem->r_offset != 0)
>   				rds_stats_inc(s_page_remainder_hit);
>
> -			rem->r_offset += bytes;
> -			if (rem->r_offset == PAGE_SIZE) {
> +			rem->r_offset += ALIGN(bytes, 8);
> +			if (rem->r_offset >= PAGE_SIZE) {
>   				__free_page(rem->r_page);
>   				rem->r_page = NULL;
>   			}
>

From: santosh shilimkar <santosh.shilimkar@oracle.com>
Date: Fri, 8 Apr 2016 12:44:39 -0700

> On 4/7/2016 4:57 AM, Shamir Rabinovitch wrote:
>> Fix issue in 'rds_ib_cong_recv' when accessing unaligned memory
>> allocated by 'rds_page_remainder_alloc' using uint64_t pointer.
>>
> Sorry I still didn't follow this change still. What exactly is the
> problem.

You can't stop the offset at non-8byte intervals, because the chunks
being used in these arenas can have 64-bit values in it, which must be
8-byte aligned.

It looks extremely obvious to me.

On 4/8/2016 1:10 PM, David Miller wrote:
> From: santosh shilimkar <santosh.shilimkar@oracle.com>
> Date: Fri, 8 Apr 2016 12:44:39 -0700
>
>> On 4/7/2016 4:57 AM, Shamir Rabinovitch wrote:
>>> Fix issue in 'rds_ib_cong_recv' when accessing unaligned memory
>>> allocated by 'rds_page_remainder_alloc' using uint64_t pointer.
>>>
>> Sorry I still didn't follow this change still. What exactly is the
>> problem.
>
> You can't stop the offset at non-8byte intervals, because the chunks
> being used in these arenas can have 64-bit values in it, which must be
> 8-byte aligned.
>
I see. Thanks for explaining it Dave.
Its fine to apply then.
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

Regards,
Santosh