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From: "Huang, Ying" <ying.huang@intel.com>
To: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Yang Shi <shy828301@gmail.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Miaohe Lin <linmiaohe@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@suse.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Minchan Kim <minchan@kernel.org>
Subject: Re: [PATCH] mm,shmem: Fix a typo in shmem_swapin_page()
Date: Wed, 04 Aug 2021 17:04:20 +0800	[thread overview]
Message-ID: <875ywl4m3v.fsf@yhuang6-desk2.ccr.corp.intel.com> (raw)
In-Reply-To: <704d597-443b-32f-84eb-524a58dd8ef@google.com> (Hugh Dickins's message of "Tue, 3 Aug 2021 22:34:52 -0700 (PDT)")

Hugh Dickins <hughd@google.com> writes:

> On Tue, 3 Aug 2021, Matthew Wilcox wrote:
>> On Tue, Aug 03, 2021 at 04:14:38PM +0800, Huang, Ying wrote:
>> > Matthew Wilcox <willy@infradead.org> writes:
>> > > But I REALLY REALLY REALLY want a reproducer.  Right now, I have a hard
>> > > time believing this, or any of the other races can really happen.
>> > 
>> > I think the race is only theoretical too.  Firstly, swapoff is a rare
>> > operations in practice; secondly, the race window is really small.
>> 
>> So do something to provoke it.  Widen the window.  Put an msleep(1000)
>> between *pagep = NULL and the call to get_swap_device().  That's assuming
>> that the swapon/swapoff loop that I proposed doesn't work.  Did you
>> try it?
>
> I've been doing that swapon/swapoff loop for years, while running kernel
> builds on tmpfs going out to swap; for better or worse on baremetal not VM.
>
> You're right that few will ever need that level of reliability; but it
> has caught problems from time to time, and I do insist on fixing them.
>
> I'm not as insistent as you on wanting a reproducer; and we all take pride
> sometimes in fixing ever more inconceivable bugs.  I'm not against that,
> but it's easy to end up with a fix more dangerous than what it claims to
> fix, rather like with random newbie cleanups.

Yes.  I totally agree, bug fixing is hard.

Best Regards,
Huang, Ying

  reply	other threads:[~2021-08-04  9:04 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-23  8:00 Huang Ying
2021-07-23 11:10 ` David Hildenbrand
2021-07-23 20:23 ` Hugh Dickins
2021-07-23 21:53   ` Matthew Wilcox
2021-08-03  8:14     ` Huang, Ying
2021-08-03 12:01       ` Matthew Wilcox
2021-08-04  5:34         ` Hugh Dickins
2021-08-04  9:04           ` Huang, Ying [this message]
2021-08-05 23:08           ` Yang Shi
2021-08-06  6:01             ` Hugh Dickins
2021-08-06 20:37               ` Yang Shi
2021-08-09 21:26                 ` Yang Shi
2021-08-09 23:43                   ` Huang, Ying
2021-08-10  1:11                     ` Yang Shi
2021-08-04  9:01         ` Huang, Ying
2021-07-28 13:03   ` huang ying
2021-08-03  8:06     ` Huang, Ying
2021-08-03 11:59       ` Matthew Wilcox
2021-08-04  4:28       ` Hugh Dickins
2021-08-04  6:42     ` Hugh Dickins
2021-08-04  8:59       ` Huang, Ying

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