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From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <yang.shi@linux.alibaba.com>,
	willy@infradead.org, ldufour@linux.vnet.ibm.com,
	kirill@shutemov.name, akpm@linux-foundation.org,
	peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
	alexander.shishkin@linux.intel.com, jolsa@redhat.com,
	namhyung@kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC v7 PATCH 4/4] mm: unmap special vmas with regular do_munmap()
Date: Fri, 10 Aug 2018 13:59:37 +0200
Message-ID: <20180810115937.GB1644@dhcp22.suse.cz> (raw)
In-Reply-To: <521a7d54-efdb-2401-c677-3f5fcbad557b@suse.cz>

On Fri 10-08-18 11:51:54, Vlastimil Babka wrote:
> On 08/10/2018 01:36 AM, Yang Shi wrote:
> > Unmapping vmas, which have VM_HUGETLB | VM_PFNMAP flag set or
> > have uprobes set, need get done with write mmap_sem held since
> > they may update vm_flags.
> > 
> > So, it might be not safe enough to deal with these kind of special
> > mappings with read mmap_sem. Deal with such mappings with regular
> > do_munmap() call.
> > 
> > Michal suggested to make this as a separate patch for safer and more
> > bisectable sake.
> 
> Hm I believe Michal meant the opposite "evolution" though. Patch 2/4
> should be done in a way that special mappings keep using the regular
> path, and this patch would convert them to the new path. Possibly even
> each special case separately.

yes, that is what I meant. Each of the special case should have its own
patch and changelog explaining why it is safe.
-- 
Michal Hocko
SUSE Labs

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-09 23:35 [RFC v7 PATCH 0/4] mm: zap pages with read mmap_sem in munmap for large mapping Yang Shi
2018-08-09 23:36 ` [RFC v7 PATCH 1/4] mm: refactor do_munmap() to extract the common part Yang Shi
2018-08-10 10:20   ` Vlastimil Babka
2018-08-10 17:41   ` Matthew Wilcox
2018-08-10 18:23     ` Yang Shi
2018-08-09 23:36 ` [RFC v7 PATCH 2/4] mm: mmap: zap pages with read mmap_sem in munmap Yang Shi
2018-08-10 17:57   ` Matthew Wilcox
2018-08-10 18:26     ` Yang Shi
2018-08-09 23:36 ` [RFC v7 PATCH 3/4] uprobes: make vma_has_uprobes non-static Yang Shi
2018-08-09 23:36 ` [RFC v7 PATCH 4/4] mm: unmap special vmas with regular do_munmap() Yang Shi
2018-08-10  9:51   ` Vlastimil Babka
2018-08-10 11:59     ` Michal Hocko [this message]
2018-08-10 16:51     ` Yang Shi
2018-08-10 10:46   ` Vlastimil Babka
2018-08-10 17:00     ` Yang Shi

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