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[209.85.208.176]) by smtp.gmail.com with ESMTPSA id c5sm2174208ljj.17.2021.05.25.10.28.55 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 May 2021 10:28:55 -0700 (PDT) Received: by mail-lj1-f176.google.com with SMTP id t17so22491147ljd.9 for ; Tue, 25 May 2021 10:28:55 -0700 (PDT) X-Received: by 2002:a2e:c52:: with SMTP id o18mr21000635ljd.411.1621963735464; Tue, 25 May 2021 10:28:55 -0700 (PDT) MIME-Version: 1.0 References: <20210525083344.162377-1-aneesh.kumar@linux.ibm.com> <20210525083344.162377-2-aneesh.kumar@linux.ibm.com> In-Reply-To: <20210525083344.162377-2-aneesh.kumar@linux.ibm.com> From: Linus Torvalds Date: Tue, 25 May 2021 07:28:39 -1000 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 2/2] mm/mremap: Fix race between MOVE_PUD mremap and pageout To: "Aneesh Kumar K.V" Cc: Linux-MM , Andrew Morton , Michael Ellerman , linuxppc-dev , Kalesh Singh , Nick Piggin , Joel Fernandes , Christophe Leroy , "Kirill A . Shutemov" Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=KjhTMVML; dmarc=none; spf=pass (imf24.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.167.43 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5D9B3A0001C9 X-Stat-Signature: wncrpfni4omc1hgw5dui88jhnrh18is9 X-HE-Tag: 1621963732-418550 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, May 24, 2021 at 10:34 PM Aneesh Kumar K.V wrote: > > @@ -221,6 +222,9 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw) > spin_unlock(pvmw->pte_ptl); > if (pvmw->pmd_ptl) > spin_unlock(pvmw->pmd_ptl); > + if (pvmw->pud_ptl) > + spin_unlock(pvmw->pud_ptl); > + > } You have this habit of adding odd whitespace.. But yes, this seems to be the right way to fix the races properly. The pageout code is special, the pageout code is normally not critical, so it's the pageout code that should go the extra mile to make up for the fact that it doesn't hold the mmap_sem like good page table modification codepaths do. Linus