linux-kernel - Re: [PATCH] adjust/fix LDT handling for Xen

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Date:	Fri, 11 Jan 2008 10:08:44 +0000
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Jiri Slaby" <jirislaby@...il.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>, <linux-kernel@...r.kernel.org>,
	"Jeremy Fitzhardinge" <jeremy@...source.com>
Subject: Re: [PATCH] adjust/fix LDT handling for Xen

>> --- linux-2.6.24-rc7/arch/x86/kernel/ldt_32.c	2008-01-10 16:53:54.000000000 +0100
>> +++ 2.6.24-rc7-x86-xen-ldt/arch/x86/kernel/ldt_32.c	2008-01-09 13:59:50.000000000 +0100
>[...]
>> @@ -73,7 +72,7 @@ static int alloc_ldt(mm_context_t *pc, u
>>  		if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
>>  			vfree(oldldt);
>>  		else
>> -			kfree(oldldt);
>> +			put_page(virt_to_page(oldldt));
>>  	}
>>  	return 0;
>>  }
>> @@ -117,7 +116,7 @@ void destroy_context(struct mm_struct *m
>>  		if ((unsigned)mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
>>  			vfree(mm->context.ldt);
>>  		else
>> -			kfree(mm->context.ldt);
>> +			put_page(virt_to_page(mm->context.ldt));
>
>why not free_page() with all those checks if it is correct virt address which it 
>brings?

I followed the combination I found elsewhere - __get_free_page/put_page
or alloc_page/free_page. I admit that I'm unclear about when/why to use
one vs. the other pair.

Jan

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