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From: Jann Horn <jannh@google.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Hugh Dickins <hughd@google.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	Linux-MM <linux-mm@kvack.org>,
	Kalesh Singh <kaleshsingh@google.com>,
	"Joel Fernandes \(Google\)" <joel@joelfernandes.org>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Andrew Morton <akpm@linux-foundation.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 6/6] mm/mremap: hold the rmap lock in write mode when moving page table entries.
Date: Fri, 11 Jun 2021 10:11:19 +0200	[thread overview]
Message-ID: <CAG48ez3=gDRSB02aL84-A54jmPTja3BS0imje-PQywgidRuPxA@mail.gmail.com> (raw)
In-Reply-To: <20210610083549.386085-7-aneesh.kumar@linux.ibm.com>

On Thu, Jun 10, 2021 at 10:35 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
> To avoid a race between rmap walk and mremap, mremap does take_rmap_locks().
> The lock was taken to ensure that rmap walk don't miss a page table entry due to
> PTE moves via move_pagetables(). The kernel does further optimization of
> this lock such that if we are going to find the newly added vma after the
> old vma, the rmap lock is not taken. This is because rmap walk would find the
> vmas in the same order and if we don't find the page table attached to
> older vma we would find it with the new vma which we would iterate later.
[...]
> Fixes: 2c91bd4a4e2e ("mm: speed up mremap by 20x on large regions")
> Fixes: c49dd3401802 ("mm: speedup mremap on 1GB or larger regions")

probably also "Cc: stable@vger.kernel.org"?

      reply	other threads:[~2021-06-11  8:12 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-10  8:35 [PATCH 0/6] mremap fixes Aneesh Kumar K.V
2021-06-10  8:35 ` [PATCH 1/6] selftest/mremap_test: Update the test to handle pagesize other than 4K Aneesh Kumar K.V
2021-06-10  8:35 ` [PATCH 2/6] selftest/mremap_test: Avoid crash with static build Aneesh Kumar K.V
2021-06-10  8:35 ` [PATCH 3/6] mm/mremap: Convert huge PUD move to separate helper Aneesh Kumar K.V
2021-06-10 22:03   ` Hugh Dickins
2021-06-10  8:35 ` [PATCH 4/6] mm/mremap: Don't enable optimized PUD move if page table levels is 2 Aneesh Kumar K.V
2021-06-10  8:35 ` [PATCH 5/6] mm/mremap: Use pmd/pud_poplulate to update page table entries Aneesh Kumar K.V
2021-06-10 18:16   ` Linus Torvalds
2021-06-13  9:06     ` Aneesh Kumar K.V
2021-06-13 10:50       ` Matthew Wilcox
2021-06-13 11:13         ` Aneesh Kumar K.V
2021-06-14  5:27           ` Christophe Leroy
2021-06-13 18:53       ` Linus Torvalds
2021-06-10  8:35 ` [PATCH 6/6] mm/mremap: hold the rmap lock in write mode when moving " Aneesh Kumar K.V
2021-06-11  8:11   ` Jann Horn [this message]

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