linux-kernel - Re: [PATCH] pramdisk: new block disk driver to perform persistent storage

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Date:	Mon, 21 Sep 2015 17:30:07 +0800
From:	Lin Yongting <linyongting@...wei.com>
To:	Ross Zwisler <ross.zwisler@...ux.intel.com>
CC:	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"axboe@...com" <axboe@...com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"richard@....at" <richard@....at>,
	"willy@...ux.intel.com" <willy@...ux.intel.com>,
	Wangxiaozhe <wangxiaozhe@...wei.com>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pramdisk: new block disk driver to perform persistent
 storage


On 2015/9/19 0:18, Ross Zwisler wrote:
> On Fri, Sep 18, 2015 at 03:46:30PM +0800, Lin Yongting wrote:
>> In embed devices, user space applications will use reserved memory
>> (i.e. persistent memory) to store business data, the data is kept
>> in this memory region after system rebooting or panic.
>>
>> pramdisk is a block disk driver based on Persistent memory, it provide
>> file system interface for application to read/write data in persistent
>> memory. Application can use pramdisk to store log file or business data
>> in persistent memory in the way of file system operation, avoid operating
>> or managing memory directly.
>>
>> pramdisk support multiple Persistent menory regions and each one is a
>> block device named as /dev/pram<N>.
>>
>> Usage:
>> modprobe pramdisk.ko pmem=<size1>@<addr2> [ pmem=<size2>@<addr2> ... ]
>>
>> For example:
>>    modprobe pramdisk.ko pmem=20M@...0M pmem=20M@...0M
>>    mkfs.ext3 /dev/pram1
>>    mkdir /tmp/test1
>>    mount -t ext3 /dev/pram1 /tmp/test1
>>
>> Signed-off-by: Lin Yongting <linyongting@...wei.com>
>> Signed-off-by: Wang xiaozhe <wangxiaozhe@...wei.com>
>
> I think you already have this functionality with the PMEM driver and the
> memmap=nn[KMG]!ss[KMG] command line parameter?  What are you trying to
> accomplish with this driver that you can't do with PMEM?

Hi Ross, thanks!

I dig into nvdimm sub-system these two day and found that PMEM can make Reserved Memory as
block disk to mount file system on it.

But I am curious about two things:
1. seems memmap command line parameter is not available at ARM arch. Can we use module
    parameter rather than kernel command parameter?
2. If I specified two memmap regions(which they are Adjacent to each other), Can we get
    tow block device?

Thanks Again.

Best Regards!

-- Lin Yongting


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