[dm-devel] Persistent memory interface

[Doug Dumitru]

Mikulas,

Can you send me a link to this driver.  I need to implement a "real" and
"correct" driver for a PMC Sierra card, so I need to pay attention to the
atomic issue you described.

Doug Dumitru
EasyCo LLC


On Fri, Jun 19, 2015 at 9:33 AM, Mikulas Patocka <mpatocka at redhat.com>
wrote:

> Hi
>
> I looked at the new the persistent memory block device driver
> (drivers/block/pmem.c and arch/x86/kernel/pmem.c) and it seems that the
> interface between them is incorrect.
>
> If I want to use persistent memory in another driver, for a different
> purpose, how can I make sure that that drivers/block/pmem.c doesn't attach
> to this piece of memory and export it? It seems not possible.
> drivers/block/pmem.c attaches to everything without regard that there may
> be other users of persistent memory.
>
> I think a correct solution would be to add a partition table at the
> beginning of persistent memory area and this partition table would
> describe which parts belong to which programs - so that different programs
> could use persistent memory and not step over each other's data. Is there
> some effort to standardize the partition table ongoing?
>
>
> BTW. some journaling filesystems assume that 512-byte sector is written
> atomically. drivers/block/pmem.c breaks this requirement. Persistent
> memory only gurantees 8-byte atomic writes.
>
> Mikulas
>
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>



-- 
Doug Dumitru
EasyCo LLC
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