linux-kernel - Re: [Linux-nvdimm] [PATCH v2 08/20] libnd, nd_acpi: regions (block-data-window, persistent memory, volatile memory)

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Date:	Thu, 28 May 2015 12:36:16 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Neil Brown <neilb@...e.de>,
	Greg KH <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>
Subject: Re: [Linux-nvdimm] [PATCH v2 08/20] libnd, nd_acpi: regions
 (block-data-window, persistent memory, volatile memory)

On Sat, 2015-05-09 at 16:55 -0700, Dan Williams wrote:
> On Mon, May 4, 2015 at 1:26 PM, Toshi Kani <toshi.kani@...com> wrote:
> > On Tue, 2015-04-28 at 14:24 -0400, Dan Williams wrote:
 :
> >
> > The libnd does not support memdev->flags, which contains "Memory Device
> > State Flags" defined in Table 5-129 of ACPI 6.0.  In case of major
> > errors, we should only allow a failed NVDIMM be accessed with read-only
> > for possible data recovery (or not allow any access when the data is
> > completely lost), and should not let users operate normally over the
> > corrupted data until the error is dealt properly.
> 
> I agree with setting read-only access when these flags show that the
> battery is not ready to persist new writes, but I don't think we
> should block access in the case where the restore from flash failed.
> If the data is potentially corrupted we should log that fact, but
> otherwise enable access.  I.e. potentially corrupt data is better than
> unavailable data.  It's up to filesystem or application to maintain
> its own checksums to catch data corruption.
> 
> > Can you set memdev->flags to nd_region(_desc) so that the pmem driver
> > can check the status in nd_pmem_probe()?  nd_pmem_probe() can then set
> > the disk read-only or fail probing, and log errors accordingly.
> 
> Will do.

I do not see this change in v4.  Is this part of the pending changes
behind this release?

Thanks,
-Toshi

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