Re: [PATCH 3/3] pmem: Allow request_mem to fail, (CONFIG_BLK_DEV_PMEM_IGNORE_REQUEST_MEM_RET)

From: Boaz Harrosh
Date: Wed Feb 18 2015 - 04:58:17 EST

On 02/17/2015 10:52 PM, Ross Zwisler wrote:
> On Mon, 2015-02-16 at 13:24 +0200, Boaz Harrosh wrote:
>> With old Kernels there was a bug in x86 where any unknown
>> memory chip type would come up BUSY when calling
>> request_mem_region_exclusive().
>> So for pmem to work with old Kernels and real NvDIMM chips
>> we have a new Kconfig option CONFIG_BLK_DEV_PMEM_IGNORE_REQUEST_MEM_RET.
>> People have been running with hacked up pmem that will ignore
>> the return code from request_mem_region_exclusive. So here it is
>> official
>> Signed-off-by: Boaz Harrosh <boaz@xxxxxxxxxxxxx>

Hi Ross, good morning

> I'm confused - I thought that this behavior was fixed by patch 1/3?
> With that patch this memory reservation should not fail, correct?

Yes, I have tested it extensively and PATCH-1/3 fixes this problem
for sure.

> If so, why do we need this patch?

I put in this patch for people that do-not-want/cannot compile their
own Kernel but have a need for pmem.c regardless. I will not include
this patch in the final submitted Kernel. Given that patch-1 gets
accepted before the merge of pmem.

Lets say that patch-1 and patch-3 are either or. A tree
that has 1/3 does not need 3/3, a tree that does not have 1/3 needs



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