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

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Date:	Mon, 21 Sep 2015 17:35:49 +0800
From:	Lin Yongting <linyongting@...wei.com>
To:	Dan Williams <dan.j.williams@...el.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
CC:	Jens Axboe <axboe@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Richard Weinberger <richard@....at>,
	Matthew Wilcox <willy@...ux.intel.com>,
	<wangxiaozhe@...wei.com>, Ingo Molnar <mingo@...nel.org>,
	Greg KH <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 0:41, Dan Williams wrote:
> On Fri, Sep 18, 2015 at 9:18 AM, Ross Zwisler
> <ross.zwisler@...ux.intel.com> 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?
>
> Moreover, if your embedded firmware publishes persistent memory ranges
> you can reuse the drivers/nvdimm/e820.c driver.  As long as your
> platform code in the kernel names those iomem_resource(s) as
> ""Persistent Memory (legacy)" they will be auto discovered and
> surfaced by the libnvidmm sub-system.
>

Thanks Dan!

Seems nvdimm sub-system can figure out my requirement.

Actually, my system is ARM arch, there is no any firmware but just a DDR memory. We reserved a memory region
which is out of OS-memory to store data Persistently, this memory region will not clear in rebooting or panic
as long as the power is not cut off.
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