Why the region area don't decrease 1 in function sanity_check_meminfo?

Dear all,

If system has defined CONFIG_SPARSEMEM, that va() and pa() have been
redefiend, like this,

 "
 #define __phys_to_virt(phys)						\
 	((phys) >= 0x80000000 ?	(phys) - 0x80000000 + PAGE_OFFSET2 :	\
 	 (phys) >= 0x20000000 ?	(phys) - 0x20000000 + PAGE_OFFSET1 :	\
 	 (phys) + PAGE_OFFSET)

 #define __virt_to_phys(virt)						\
 	 ((virt) >= PAGE_OFFSET2 ? (virt) - PAGE_OFFSET2 + 0x80000000 :	\
 	  (virt) >= PAGE_OFFSET1 ? (virt) - PAGE_OFFSET1 + 0x20000000 :	\
 	  (virt) - PAGE_OFFSET)

"
But this line "__va(bank->start + bank->size) < __va(bank->start)"
always assume that the next bank's vaddr is bigger than it.
Yes, we can defined these two MACROS carefully to avoid this problem.
How do you think it. Can you shed some light on what the correct
solution might be?

steve

quoted

Date: Tue, 24 Jul 2012 18:54:30 +0800
From: ??? <redacted>
To: will.deacon at arm.com, catalin.marinas at arm.com
Cc: linux-arm-kernel at lists.infradead.org
Subject: Why the region area don't decrease 1 in function
	sanity_check_meminfo?
Message-ID:
	[ref]
Content-Type: text/plain; charset=ISO-8859-1

In this function, have these codes:

/*
		 * Check whether this memory bank would partially overlap
		 * the vmalloc area.
		 */
		if (__va(bank->start + bank->size) > vmalloc_min ||
		    __va(bank->start + bank->size) < __va(bank->start)) {
			unsigned long newsize = vmalloc_min - __va(bank->start);
			printk(KERN_NOTICE "Truncating RAM at %.8llx-%.8llx "
			       "to -%.8llx (vmalloc region overlap).\n",
			       (unsigned long long)bank->start,
			       (unsigned long long)bank->start + bank->size - 1,
			       (unsigned long long)bank->start + newsize - 1);
			bank->size = newsize;
		}

Dear all,


I don't known why the memory region have not decrease 1, i think it
should be decreased(like this , (__va(bank->start + bank->size
-1))because in sparse memory system,  this address bank->start +
bank->size is belong to another bank, so this method is not correctly.

Please indicate whether my understanding is correct.

Thanks.


Steve



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End of linux-arm-kernel Digest, Vol 36, Issue 687
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--
Steve Zhan

-- 
Steve Zhan