Re: [PATCH -mm] swsusp: support creating bigger images

[Nick Piggin <nickpiggin@yahoo.com.au>]

Hugh Dickins wrote:

>On Tue, 9 May 2006, Rafael J. Wysocki wrote:
>
>>On Tuesday 09 May 2006 09:33, Andrew Morton wrote:
>>    
>>
>>>task_struct.mm can sometimes be NULL.  This function assumes that it will
>>>never be NULL.  That makes it a somewhat risky interface.  Are we sure it
>>>can never be NULL?
>>>
>>Well, now it's only called for task == current, but I can add a check.
>>
>
>Better fold it into the (renamed and recommented) page_to_copy,
>applying only to current.
>
>The "use" of page_table_lock there is totally bogus.  Normally you
>need down_read(&current->mm->mmap_sem) to walk that vma chain; but
>I'm guessing you have everything sufficiently frozen here that you
>don't need that.
>

I have to admit that I suggested making this change, because the
function was sufficently generic looking. I guess the mm == NULL
case should logically return 0... unless you did that, making
page_mapped_by_task use current still leaves the burden of ensuring
->mm != NULL on the caller.

But I don't much mind which way the consensus goes.

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