Re: [PATCH] powerpc: Fix assmption of end_of_DRAM() returns end address

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 06 Jun 2012 15:30:17 +1000

On Wed, 2012-06-06 at 00:46 +0000, Bhushan Bharat-R65777 wrote:

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memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Shouldn't we instead fix it the other way around ? IE, make
memblock_end_of_DRAM() does what the name implies, which is to

return

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the last byte of DRAM, and fix the -other- callers not to make bad
assumptions ?

That was my impression too when I saw this patch.

Initially I also intended to do so. I initiated a email on linux-mm@
subject "memblock_end_of_DRAM()  return end address + 1" and the only
response I received from Andrea was:

"
It's normal that "end" means "first byte offset out of the range". End
= not ok.
end = start+size.
This is true for vm_end too. So it's better to keep it that way.
My suggestion is to just fix point 1 below and audit the rest :)
"

Oh well, I don't care enough to fight this battle in my current state so
unless Dave has more stamina than I have today, I'm ok with the patch.

I'm definitely without the samina to fight something like this right now :)