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From: Andrew Morton <>
To: Matthew Wilcox <>
Cc: "Aneesh Kumar K.V" <>,
	Mike Kravetz <>,,
Subject: Re: [RFC PATCH] mm/hugetlb: make hugetlb_lock irq safe
Date: Wed, 5 Sep 2018 12:58:46 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, 5 Sep 2018 06:48:48 -0700 Matthew Wilcox <> wrote:

> > I didn't. The reason I looked at current patch is to enable the usage of
> > put_page() from irq context. We do allow that for non hugetlb pages. So was
> > not sure adding that additional restriction for hugetlb
> > is really needed. Further the conversion to irqsave/irqrestore was
> > straightforward.
> straightforward, sure.  but is it the right thing to do?  do we want to
> be able to put_page() a hugetlb page from hardirq context?

Calling put_page() against a huge page from hardirq seems like the
right thing to do - even if it's rare now, it will presumably become
more common as the hugepage virus spreads further across the kernel. 
And the present asymmetry is quite a wart.

That being said, arch/powerpc/mm/mmu_context_iommu.c:mm_iommu_free() is
the only known site which does this (yes?) so perhaps we could put some
stopgap workaround into that site and add a runtime warning into the
put_page() code somewhere to detect puttage of huge pages from hardirq
and softirq contexts.

And attention will need to be paid to -stable backporting.  How long
has mm_iommu_free() existed, and been doing this?

  reply	other threads:[~2018-09-05 19:58 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-05 11:23 [RFC PATCH] mm/hugetlb: make hugetlb_lock irq safe Aneesh Kumar K.V
2018-09-05 13:04 ` Matthew Wilcox
2018-09-05 13:26   ` Aneesh Kumar K.V
2018-09-05 13:48     ` Matthew Wilcox
2018-09-05 19:58       ` Andrew Morton [this message]
2018-09-05 21:35         ` Mike Kravetz
2018-09-05 22:00           ` Andrew Morton
2018-09-05 23:07             ` Matthew Wilcox
2018-09-05 23:51               ` Mike Kravetz
2018-09-06  4:03                 ` Aneesh Kumar K.V
2018-09-06 11:19                 ` Michal Hocko
2018-09-06  3:58           ` Aneesh Kumar K.V
2018-09-06  3:54         ` Aneesh Kumar K.V
2018-09-06  4:00       ` Aneesh Kumar K.V

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