simplify pstore-blk

[廖威雄]

hi Christoph,

On Fri, Oct 16, 2020 at 9:27 PM Christoph Hellwig <hch at lst.de> wrote:
>
> Hi all,
>
> this series cleans up and massively simplifies the pstore-blk code,
> please take a look.

Thanks for your code. I am going to redesign pstore/blk referred to
your idea.

I want to split pstore/blk into two parts, pstore/dev and pstore/blk.
pstore/dev is a common layer that handles all configurations
for users. All devices including block devices, ram devices and
mtd devices register to pstore/dev with operations and some flags.

Besides that, we can delete the codes for the block device to
register a panic_wirte() interface since there is no block device
needed. But it should be easy to implement registering if necessary.