linux-kernel - Re: [PATCH] mm: dont call mmu_notifier_invalidate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALYGNiN4v4b_AJW10wVyy1XnapzwLk8Pod89sb3E-b3c81SoVw@mail.gmail.com>
Date:	Thu, 29 May 2014 11:19:27 +0400
From:	Konstantin Khlebnikov <koct9i@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: dont call mmu_notifier_invalidate_page during munlock

On Thu, May 29, 2014 at 3:09 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Wed, 28 May 2014 11:59:55 +0400 Konstantin Khlebnikov <koct9i@...il.com> wrote:
>
>> try_to_munlock() searches other mlocked vmas, it never unmaps pages.
>> There is no reason for invalidation because ptes are left unchanged.
>>
>> ...
>>
>> --- a/mm/rmap.c
>> +++ b/mm/rmap.c
>> @@ -1225,7 +1225,7 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
>>
>>  out_unmap:
>>       pte_unmap_unlock(pte, ptl);
>> -     if (ret != SWAP_FAIL)
>> +     if (ret != SWAP_FAIL && TTU_ACTION(flags) != TTU_MUNLOCK)
>>               mmu_notifier_invalidate_page(mm, address);
>>  out:
>>       return ret;
>
> The patch itself looks reasonable but there is no such thing as
> try_to_munlock().  I rewrote the changelog thusly:

Wait, what? I do have function with this name in my sources. It calls rmap_walk
with callback try_to_unmap_one and action TTU_MUNLOCK. This is the place
where TTU_MUNLOCK is used, I've mentioned it as entry point of this logic.

>
> : In its munmap mode, try_to_unmap_one() searches other mlocked vmas, it
> : never unmaps pages.  There is no reason for invalidation because ptes are
> : left unchanged.
>
> Also, the name try_to_unmap_one() is now pretty inaccurate/incomplete.
> Perhaps if someone is feeling enthusiastic they might think up a better
> name for the various try_to_unmap functions and see if we can
> appropriately document try_to_unmap_one().

I thought about moving mlock part out of try_to_unmap_one() into
separate function,
but normal unmap needs this part too...
Anyway I want to make try_to_unmap_one() static, this is internal function now.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/