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I'm attempting to mount a partition from a NAS and the block size is 65536 bytes, this is above my distribution's precompiled kernel memory paging size of 4KiB, so I cannot mount it normally.

Which kernel compilation parameters would I need to change to get a memory paging size large enough? Would it be possible under the x86-64 architecture?

EDIT: There doesn't seem to be an option for it in make xconfig unless I'm just missing it.

From page_types.h under arch\x86\include\asm

/* PAGE_SHIFT determines the page size */
#define PAGE_SHIFT  12
#define PAGE_SIZE   (_AC(1,UL) << PAGE_SHIFT)
#define PAGE_MASK   (~(PAGE_SIZE-1))`

It doesn't look to be configurable. I could change this number directly to 16 and it would probably make pretty explosions and destroy Tokyo. I shall probably try it later this evening.

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2 Answers 2

You need to change your kernel page size. Not recommending it, but possible I suppose.

It has nothing to do with your architecture though. (i.e. if its possible, it can be done with your architecture, and if it can't its not because of your architecture)

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superuser.com/questions/242055/… ;) I also definitely have an ext4 partition with 64k block size. –  OmnipotentEntity May 31 '11 at 20:25
    
Didn't see that :) but it seems that the upvoted answer agrees with me. I guess that means that you need to change the kernel page size to get it to work. –  soandos May 31 '11 at 20:27
    
Yes, and my specific question was is it possible with the x86_64 arch and if so, which parameters do I need to change. :D –  OmnipotentEntity May 31 '11 at 20:32
    
So yes, it is, you need to change the kernel page size in the kernel. It not some option lying around, but probably (speculation) will require a recompilation of the kernel (or have someone do it for you). Why does it matter btw? –  soandos May 31 '11 at 20:36
    
Yes, it will require recompiling the kernel, this is not that big of a deal to me, I just need to know which parameter I need to change in the kernel's configuration wizard. All of this I mentioned in the original question btw. ;) It matters because my NAS died and I need the information off of it. –  OmnipotentEntity May 31 '11 at 20:38
up vote 0 down vote accepted

From page_types.h under arch\x86\include\asm

/* PAGE_SHIFT determines the page size */
#define PAGE_SHIFT  12
#define PAGE_SIZE   (_AC(1,UL) << PAGE_SHIFT)
#define PAGE_MASK   (~(PAGE_SIZE-1))

changing the 12 into a 16 results in

arch/x86/kernel/head64.c: In function ‘x86_64_start_kernel’:
arch/x86/kernel/head64.c:71: error: negative width in bit-field ‘<anonymous>’
make[2]: *** [arch/x86/kernel/head64.o] Error 1

Because this is just sanity checking code for modules offsets it seems that changing the memory paging size has a lot of unintended side effects which will make this far from simple. I guess I'm stuck with finding another arch to run on. :(

Here is a list of the archs that support 64KiB or greater page sizes: ia64, mips, pa-risc, powerpc, sh, sparc64. So it looks like my best bet it to find an old-PPC Mac.

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