From: Andrew Morton <akpm@linux-foundation.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] mm/hugetlb: make hugetlb_lock irq safe
Date: Wed, 5 Sep 2018 12:58:46 -0700 [thread overview]
Message-ID: <20180905125846.eb0a9ed907b293c1b4c23c23@linux-foundation.org> (raw)
In-Reply-To: <20180905134848.GB3729@bombadil.infradead.org>
On Wed, 5 Sep 2018 06:48:48 -0700 Matthew Wilcox <willy@infradead.org> 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?
next prev parent 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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