netdev - Re: [RFC net-next 04/17] net/smc: Decouple sf and attached send_buf in smc

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Message-ID: <96d21746-e374-4235-a567-2a7343060fe4@linux.ibm.com>
Date: Mon, 11 Aug 2025 14:03:53 +0200
From: Alexandra Winter <wintera@...ux.ibm.com>
To: dust.li@...ux.alibaba.com, David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Andrew Lunn <andrew+netdev@...n.ch>,
        "D. Wythe" <alibuda@...ux.alibaba.com>,
        Sidraya Jayagond <sidraya@...ux.ibm.com>,
        Wenjia Zhang
 <wenjia@...ux.ibm.com>,
        Julian Ruess <julianr@...ux.ibm.com>
Cc: netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thorsten Winkler <twinkler@...ux.ibm.com>,
        Simon Horman <horms@...nel.org>,
        Mahanta Jambigi <mjambigi@...ux.ibm.com>,
        Tony Lu
 <tonylu@...ux.alibaba.com>, Wen Gu <guwen@...ux.alibaba.com>,
        Halil Pasic <pasic@...ux.ibm.com>, linux-rdma@...r.kernel.org
Subject: Re: [RFC net-next 04/17] net/smc: Decouple sf and attached send_buf
 in smc_loopback



On 11.08.25 13:35, Alexandra Winter wrote:
> 
> 
> On 10.08.25 16:00, Dust Li wrote:
>> On 2025-08-06 17:41:09, Alexandra Winter wrote:
> [...]
>>>
>>> diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
>>> index 48a1b1dcb576..fe5f48d14323 100644
>>> --- a/net/smc/smc_core.h
>>> +++ b/net/smc/smc_core.h
>>> @@ -13,6 +13,7 @@
>>> #define _SMC_CORE_H
>>>
>>> #include <linux/atomic.h>
>>> +#include <linux/types.h>
>>> #include <linux/smc.h>
>>> #include <linux/pci.h>
>>> #include <rdma/ib_verbs.h>
>>> @@ -221,12 +222,16 @@ struct smc_buf_desc {
>>> 					/* virtually contiguous */
>>> 		};
>>> 		struct { /* SMC-D */
>>> +			 /* SMC-D rx buffer: */
>>> 			unsigned short	sba_idx;
>>> 					/* SBA index number */
>>> 			u64		token;
>>> 					/* DMB token number */
>>> 			dma_addr_t	dma_addr;
>>> 					/* DMA address */
>>> +			/* SMC-D tx buffer */
>>> +			bool		is_attached;
>>> +					/* no need for explicit writes */
>>
>> Reviewed-by: Dust Li <dust.li@...ux.alibaba.com>
>>
>> A small sugguestion: there is a hole between sba_idx and token, we can
>> put is_attached in that hole.
>> Not a big deal because this is a union and SMC-R use a much large space.
>>
>> Best regards,
>> Dust
>>
> 
> Thank you very much for your throrough reviews of this series, Dust.
> 
> I put 'bool is_attached' in this place, so I could add the comments about which members
> are used for rx-buffers and which for tx-buffers.
> I find the struct smc_buf_desc a bit confusing and thought these comments would be helpful.
> Is it ok for you to leave it that way?


I hit send too fast. Obviously I can put it above sba_idx. That will reduce the hole  by 1 byte.
Changed for next version.