From: Peter Zijlstra <peterz@infradead.org>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Nadav Amit <nadav.amit@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
ldufour@linux.vnet.ibm.com,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>,
acme@kernel.org, alexander.shishkin@linux.intel.com,
jolsa@redhat.com, namhyung@kernel.org,
"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC v2 PATCH 2/2] mm: mmap: zap pages with read mmap_sem for large mapping
Date: Tue, 26 Jun 2018 09:43:44 +0200 [thread overview]
Message-ID: <20180626074344.GZ2458@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <263935d9-d07c-ab3e-9e42-89f73f57be1e@linux.alibaba.com>
On Mon, Jun 25, 2018 at 05:06:23PM -0700, Yang Shi wrote:
> By looking this deeper, we may not be able to cover all the unmapping range
> for VM_DEAD, for example, if the start addr is in the middle of a vma. We
> can't set VM_DEAD to that vma since that would trigger SIGSEGV for still
> mapped area.
>
> splitting can't be done with read mmap_sem held, so maybe just set VM_DEAD
> to non-overlapped vmas. Access to overlapped vmas (first and last) will
> still have undefined behavior.
Acquire mmap_sem for writing, split, mark VM_DEAD, drop mmap_sem. Acquire
mmap_sem for reading, madv_free drop mmap_sem. Acquire mmap_sem for
writing, free everything left, drop mmap_sem.
?
Sure, you acquire the lock 3 times, but both write instances should be
'short', and I suppose you can do a demote between 1 and 2 if you care.
next prev parent reply other threads:[~2018-06-26 7:43 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-18 23:34 [RFC v2 0/2] mm: zap pages with read mmap_sem in munmap " Yang Shi
2018-06-18 23:34 ` [RFC v2 PATCH 1/2] uprobes: make vma_has_uprobes non-static Yang Shi
2018-06-18 23:34 ` [RFC v2 PATCH 2/2] mm: mmap: zap pages with read mmap_sem for large mapping Yang Shi
2018-06-19 10:02 ` Peter Zijlstra
2018-06-19 21:13 ` Yang Shi
2018-06-20 7:17 ` Michal Hocko
2018-06-20 16:23 ` Yang Shi
2018-06-19 22:17 ` Nadav Amit
2018-06-19 23:08 ` Yang Shi
2018-06-20 0:31 ` Nadav Amit
2018-06-20 7:18 ` Michal Hocko
2018-06-20 17:12 ` Nadav Amit
2018-06-20 18:42 ` Yang Shi
2018-06-23 1:01 ` Yang Shi
2018-06-25 9:14 ` Michal Hocko
2018-06-26 0:06 ` Yang Shi
2018-06-26 7:43 ` Peter Zijlstra [this message]
2018-06-27 1:03 ` Yang Shi
2018-06-27 7:24 ` Michal Hocko
2018-06-27 17:23 ` Yang Shi
2018-06-28 11:51 ` Michal Hocko
2018-06-28 19:10 ` Yang Shi
2018-06-29 0:59 ` Yang Shi
2018-06-29 11:39 ` Michal Hocko
2018-06-29 16:50 ` Yang Shi
2018-06-29 11:34 ` Michal Hocko
2018-06-29 16:45 ` Yang Shi
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