linux-kernel - Re: [RFC PATCH 2/4] mm: Change the interface for __tlb_remove

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Message-ID: <87h9de201i.fsf@skywalker.in.ibm.com>
Date:	Tue, 31 May 2016 12:20:49 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Hillf Danton <hillf.zj@...baba-inc.com>
Cc:	"'linux-kernel'" <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [RFC PATCH 2/4] mm: Change the interface for __tlb_remove_page

Hillf Danton <hillf.zj@...baba-inc.com> writes:

>> >> @@ -1202,7 +1205,12 @@ again:
>> >>  	if (force_flush) {
>> >>  		force_flush = 0;
>> >>  		tlb_flush_mmu_free(tlb);
>> >> -
>> >> +		if (pending_page) {
>> >> +			/* remove the page with new size */
>> >> +			__tlb_adjust_range(tlb, tlb->addr);
>> >
>> > Would you please specify why tlb->addr is used here?
>> >
>> 
>> That is needed because tlb_flush_mmu_tlbonly() does a __tlb_reset_range().
>> 
> If ->addr is updated in resetting, then it is a noop here to deliver tlb->addr to
> __tlb_adjust_range().
> On the other hand, if ->addr is not updated in resetting, then it is also a noop here.
>
> Do you want to update ->addr here?
>

I don't get that question. We wanted to track the alst adjusted addr in
tlb->addr because when we do a tlb_flush_mmu_tlbonly() we does a
__tlb_reset_range(), which clears tlb->start and tlb->end. Now we need
to update the range again with the last adjusted addr before we can call
__tlb_remove_page(). Look for VM_BUG_ON(!tlb->end); in
__tlb_remove_page().

-aneesh