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

[Lin Yongting <linyongting@huawei.com>]

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@2050M pmem=20M@2150M
>>    mkfs.ext3 /dev/pram1
>>    mkdir /tmp/test1
>>    mount -t ext3 /dev/pram1 /tmp/test1
>>
>> Signed-off-by: Lin Yongting <linyongting@huawei.com>
>> Signed-off-by: Wang xiaozhe <wangxiaozhe@huawei.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