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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id em15sm471056pjb.43.2021.06.09.14.12.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 14:12:13 -0700 (PDT) Date: Wed, 9 Jun 2021 14:11:19 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.anvils To: Yang Shi cc: Hugh Dickins , Andrew Morton , "Kirill A. Shutemov" , Wang Yugui , Matthew Wilcox , Naoya Horiguchi , Alistair Popple , Ralph Campbell , Zi Yan , Miaohe Lin , Minchan Kim , Jue Wang , Peter Xu , Jan Kara , Shakeel Butt , Oscar Salvador , Linux MM , Linux Kernel Mailing List Subject: Re: [PATCH v2 06/10] mm/thp: unmap_mapping_page() to fix THP truncate_cleanup_page() In-Reply-To: Message-ID: <50eb41a-e6f8-e566-20ef-22fb63b0a529@google.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b="WUOI/Ifg"; spf=pass (imf18.hostedemail.com: domain of hughd@google.com designates 209.85.214.177 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DFAEC200109C X-Stat-Signature: e6jenjct4dd6axz7cd5bugyqp5osspry X-HE-Tag: 1623273131-491305 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 Wed, 9 Jun 2021, Yang Shi wrote: > On Tue, Jun 8, 2021 at 9:19 PM Hugh Dickins wrote: > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -1361,7 +1361,17 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb, > > else if (zap_huge_pmd(tlb, vma, pmd, addr)) > > goto next; > > /* fall through */ > > + } else if (details && details->single_page && > > + PageTransCompound(details->single_page) && > > + next - addr == HPAGE_PMD_SIZE && pmd_none(*pmd)) { > > + /* > > + * Take and drop THP pmd lock so that we cannot return > > + * prematurely, while zap_huge_pmd() has cleared *pmd, > > + * but not yet decremented compound_mapcount(). > > + */ > > + spin_unlock(pmd_lock(tlb->mm, pmd)); > > Just a nit, why not follow the style of patch #3 to have lock and > unlock with separate lines? Good point. Doing it on one line is my own preferred style (particularly with the "take and drop lock" comment just above), carried forward from before. I simply didn't think to change this one when I agreed to change the other. You're right to question it: v3 of just this 06/10 follows. And thank you to Kirill and to you for these rapid further reviews (and for silently forgiving my screwup in omitting to Cc linux-mm and lkml on those early ones). Hugh