linux-kernel - Re: [PATCH v2 8/8] block: Init for CBD(CXL Block Device) module

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Message-ID: <c8a09654-f27e-766a-58f2-d36dffe34322@linux.dev>
Date: Wed, 25 Sep 2024 09:48:30 +0800
From: Dongsheng Yang <dongsheng.yang@...ux.dev>
To: Randy Dunlap <rdunlap@...radead.org>, axboe@...nel.dk,
 dan.j.williams@...el.com, gregory.price@...verge.com, John@...ves.net,
 Jonathan.Cameron@...wei.com, bbhushan2@...vell.com, chaitanyak@...dia.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-cxl@...r.kernel.org, linux-bcache@...r.kernel.org
Subject: Re: [PATCH v2 8/8] block: Init for CBD(CXL Block Device) module

Hi Randy,

在 2024/9/25 星期三 上午 12:35, Randy Dunlap 写道:
> Hi.
> 
> On 9/18/24 3:18 AM, Dongsheng Yang wrote:
>> diff --git a/drivers/block/cbd/Kconfig b/drivers/block/cbd/Kconfig
>> new file mode 100644
>> index 000000000000..16ffcca058c5
>> --- /dev/null
>> +++ b/drivers/block/cbd/Kconfig
>> @@ -0,0 +1,45 @@
>> +config BLK_DEV_CBD
>> +	tristate "CXL Block Device (Experimental)"
>> +	depends on DEV_DAX && FS_DAX
>> +	help
>> +	  CBD allows you to register a persistent memory device as a CBD transport.
>> +	  You can use this persistent memory as a data cache to improve your block
>> +	  device performance. Additionally, if you enable CBD_MULTIHOST, cbd allows
> 
> s/cbd/CBD/ for consistency. Or does 'cbd' here explicitly refer to the loadable module
> name?

I will use uppercase "CBD" in the next version for consistency.
> 
>> +	  you to access block devices on a remote host as if they were local disks.
>> +
>> +	  Select 'y' to build this module directly into the kernel.
>> +	  Select 'm' to build this module as a loadable kernel module.
>    +	  The module will be called cbd.
> 
>> +
>> +	  If unsure say 'N'.
>> +
>> +config CBD_CRC
>> +	bool "Enable CBD checksum"
>> +	default N
> 
> We usually omit 'default N' since that is the default default.

I explicitly added "default" here to make it clearer. In fact, I did a 
search:

find . -name 'Kconfig' -exec grep 'default n' {} + | wc -l

There are over 400+ of "default n" in the Kconfig files. （I will use 
'default n' in next version）
> 
>> +	depends on BLK_DEV_CBD
>> +	help
>> +	  When CBD_CRC is enabled, all data sent by CBD will include
>> +	  a checksum. This includes a data checksum, a submit entry checksum,
>> +	  and a completion entry checksum. This ensures the integrity of the
>> +	  data transmitted through the CXL memory device.
>> +
>> +config CBD_DEBUG
>> +	bool "Enable CBD debug"
>> +	default N
> 
> Ditto.
> 
>> +	depends on BLK_DEV_CBD
>> +	help
>> +	  When CBD_DEBUG is enabled, cbd module will print more messages
>> +	  for debugging. But that will affact performance, so do not use it
> 
> 	                               affect
> 
>> +	  in production case.
>> +
>> +config CBD_MULTIHOST
>> +	bool "multi-hosts CXL Dlock Device"
> 
> 	                      Block
> 
>> +	default N
> 
> drop default line.
> 
>> +	depends on BLK_DEV_CBD
>> +	help
>> +	  When CBD_MULTIHOST is enabled, cbd allows the use of a shared memory device
> 
> cbd or CBD?
> 
>> +	  as a cbd transport. In this mode, the blkdev and backends on different
> 
> ditto.
> 
>> +	  hosts can be connected through the shared memory device, enabling cross-node
>> +	  disk access.
>> +
>> +	  IMPORTANT: This Require your shared memory device support Hardware-consistency
> 
> 	                  requires                          supports
> 
>> +	  as CXL 3.0 described.
> 
> 	  as described in CXL 3.0.

agreed.

Thank you for your review.

Dongsheng
>