linux-kernel - Re: [PATCH 0/2] shmem: fix faulting into a hole while it's punched, take 3

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Date:	Sat, 19 Jul 2014 16:44:15 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Sasha Levin <sasha.levin@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
cc:	Vlastimil Babka <vbabka@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michel Lespinasse <walken@...gle.com>,
	Lukas Czerner <lczerner@...hat.com>,
	Dave Jones <davej@...hat.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] shmem: fix faulting into a hole while it's punched,
 take 3

On Fri, 18 Jul 2014, Sasha Levin wrote:
> On 07/17/2014 12:12 PM, Sasha Levin wrote:
> > On 07/17/2014 12:10 PM, Vlastimil Babka wrote:
> >> > On 07/15/2014 12:28 PM, Hugh Dickins wrote:
> >>> >> In the end I decided that we had better look at it as two problems,
> >>> >> the trinity faulting starvation, and the indefinite punching loop,
> >>> >> so 1/2 and 2/2 present both solutions: belt and braces.
> >> > 
> >> > I tested that with my reproducer and it was OK, but as I already said, it's not trinity so I didn't observe the new problems in the first place.
> > I've started seeing a new hang in the lru code, but I'm not sure if
> > it's related to this patch or not (the locks are the same ones, but
> > the location is very different).
> > 
> > I'm looking into that.
> 
> Hi Hugh,
> 
> The new hang I'm seeing is much simpler to analyse (compared to shmem_fallocate) and
> doesn't seem to be related. I'll send a separate mail and Cc you just in case, but
> I don't think that this patchset has anything to do with it.

Thanks for testing and following up, Sasha.  I agree, that one is
unrelated.  I've just sent a suggestion in your lru_add_drain_all thread.

> 
> Otherwise, I've been unable to reproduce the shmem_fallocate hang.

Great.  Andrew, I think we can say that it's now safe to send
1/2 shmem: fix faulting into a hole, not taking i_mutex
2/2 shmem: fix splicing from a hole while it's punched
on to Linus whenever suits you.

(You have some other patches in the mainline-later section of the
mmotm/series file: they're okay too, but not in doubt as these two were.)

Thanks,
Hugh
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