linux-kernel - Re: [PATCH v9 11/17] mm: replace vm_lock and detached flag with a reference count

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: <20250116091021.nm3nmmk2b2sd6hjj@master>
Date: Thu, 16 Jan 2025 09:10:21 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Wei Yang <richard.weiyang@...il.com>, akpm@...ux-foundation.org,
	peterz@...radead.org, willy@...radead.org, liam.howlett@...cle.com,
	lorenzo.stoakes@...cle.com, david.laight.linux@...il.com,
	mhocko@...e.com, vbabka@...e.cz, hannes@...xchg.org,
	mjguzik@...il.com, oliver.sang@...el.com,
	mgorman@...hsingularity.net, david@...hat.com, peterx@...hat.com,
	oleg@...hat.com, dave@...olabs.net, paulmck@...nel.org,
	brauner@...nel.org, dhowells@...hat.com, hdanton@...a.com,
	hughd@...gle.com, lokeshgidra@...gle.com, minchan@...gle.com,
	jannh@...gle.com, shakeel.butt@...ux.dev, souravpanda@...gle.com,
	pasha.tatashin@...een.com, klarasmodin@...il.com, corbet@....net,
	linux-doc@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v9 11/17] mm: replace vm_lock and detached flag with a
 reference count

On Wed, Jan 15, 2025 at 05:41:27PM -0800, Suren Baghdasaryan wrote:
[...]
>> >> >the case of EAGAIN.
>> >> >
>> >>
>> >> Looks good to me.
>> >>
>> >> >>
>> >> >> Maybe we can compare the event VMA_LOCK_MISS and VMA_LOCK_ABORT
>> >> >> to see the percentage of this case. If it shows this is a too rare
>> >> >> case to impact performance, we can ignore it.
>> >> >>
>> >> >> Also the event VMA_LOCK_MISS recording is removed, but the definition is
>> >> >> there. We may record it in the vma_start_read() when oldcnt is 0.
>> >> >>
>> >> >> BTW, the name of VMA_LOCK_SUCCESS confuse me a little. I thought it indicates
>> >> >> lock_vma_under_rcu() successfully get a valid vma. But seems not. Sounds we
>> >> >> don't have an overall success/failure statistic in vmstat.
>> >> >
>> >> >Are you referring to the fact that we do not increment
>> >> >VMA_LOCK_SUCCESS if we successfully locked a vma but have to retry the
>> >>
>> >> Something like this. I thought we would increase VMA_LOCK_SUCCESS on success.
>> >>
>> >> >page fault (in which we increment VMA_LOCK_RETRY instead)?
>> >> >
>> >>
>> >> I don't follow this.
>> >
>> >Sorry, I meant to say "in which case we increment VMA_LOCK_RETRY
>> >instead". IOW, when we successfully lock the vma but have to retry the
>> >pagefault, we increment VMA_LOCK_RETRY without incrementing
>> >VMA_LOCK_SUCCESS.
>> >
>>
>> Yes, this makes me confused about what VMA_LOCK_SUCCESS represents.
>
>I'll need to look into the history of why we account it this way but
>this is out of scope for this patchset.
>

Agree.


-- 
Wei Yang
Help you, Help me