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

[Lin Yongting]

On 2015/9/19 0:41, Dan Williams wrote:
> On Fri, Sep 18, 2015 at 9:18 AM, Ross Zwisler
> <ross.zwisler@xxxxxxxxxxxxxxx> 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@xxxxxxxxxx>
> > > Signed-off-by: Wang xiaozhe <wangxiaozhe@xxxxxxxxxx>
> >
> > 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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