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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id o207-20020a0dccd8000000b00568c1c919d2sm29463ywd.29.2023.07.05.17.52.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Jul 2023 17:52:51 -0700 (PDT) Date: Wed, 5 Jul 2023 17:52:40 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Alexander Gordeev cc: Hugh Dickins , Gerald Schaefer , Jason Gunthorpe , Andrew Morton , Vasily Gorbik , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Russell King , "David S. Miller" , Michael Ellerman , "Aneesh Kumar K.V" , Heiko Carstens , Christian Borntraeger , Claudio Imbrenda , Jann Horn , Vishal Moola , Vlastimil Babka , linux-arm-kernel@lists.infradead.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 07/12] s390: add pte_free_defer() for pgtables sharing page In-Reply-To: Message-ID: <8c6a4a46-2d17-8cfb-50f-f89f1d44973f@google.com> References: <54cb04f-3762-987f-8294-91dafd8ebfb0@google.com> <20230628211624.531cdc58@thinkpad-T15> <20230629175645.7654d0a8@thinkpad-T15> <7bef5695-fa4a-7215-7e9d-d4a83161c7ab@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 9FC431A000D X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: z3gbirq6tqymbns31ru38imsuap6s7i8 X-HE-Tag: 1688604772-365127 X-HE-Meta: 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 POk+GGpP 7n7gLFSM28OzEbNK6SwyH5uzrjcKE4KCJjquIxdgetNWXkzdDxCzgp0dyeNEIeHVCFMrupbwBIPN7DlaF7GzHpcPSeEAKV/qm7DWX/FxUCzUFzfLxJW5qMI7pERK/RtUcAnNi5zRZjMY4fnmKdzilashHx3qq/Dfh2KYd3Iz2Aoa/EC9g7WtVc1PUAhtbJqxYJ3JF2lzjCUMxQBKhSSx88q31vnTshj+Rzph97Nrap0X2yoyKRO5lFwr+EemdLjYStX5I1qa6rUOsZ/RxKWBhdiVy5GHUJIJE5/PRz+2vt/+FjMpxoeg4NvSM9vHH856HfLvf7KGRpxrsX8bscHbf/s8tWxNA2pwIZ5P7PJGcKixMvSncGS5Rn4oBgeZbnKynXB2T2khYNRZG8l3WCL+mUC8LqG6AzIVxoWDTlgpi//ri1E//mq8rDxqGXlb9urVEuaQKSHE7dUdo4LHuqgPil5IVDvWG6P0+ovny 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, 5 Jul 2023, Alexander Gordeev wrote: > On Sat, Jul 01, 2023 at 09:32:38PM -0700, Hugh Dickins wrote: > > On Thu, 29 Jun 2023, Hugh Dickins wrote: > > Hi Hugh, > > ... > > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > +void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable) > > +{ > > + struct page *page; > > If I got your and Claudio conversation right, you were going to add > here WARN_ON_ONCE() in case of mm_alloc_pgste(mm)? Well, Claudio approved, so I would have put it in, if we had stuck with that version which had "if (mm_alloc_pgste(mm)) {" in pte_free_defer(); but once that went away, it became somewhat irrelevant... to me anyway. But I don't mind adding it here, in the v3 I'll post when -rc1 is out, if it might help you guys - there is some point, since pte_free_defer() is a route which can usefully check for such a case, without confusion from harmless traffic from immediate frees of just-in-case allocations. But don't expect it to catch all such cases (if they exist): another category of s390 page_table_free()s comes from the PageAnon zap_deposited_table() in zap_huge_pmd(): those tables might or might not have been exposed to userspace at some time in the past. I'll add the WARN_ON_ONCE in pte_free_defer() (after checking that WARN_ON_ONCE is the one we want - I get confused by all the different flavours of WARN, and have to check the header file each time to be sure of the syntax and semantics): but be aware that it won't be checking all potential cases. Hugh > > > + page = virt_to_page(pgtable); > > + SetPageActive(page); > > + page_table_free(mm, (unsigned long *)pgtable); > > +} > > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > + > > /* > > * Base infrastructure required to generate basic asces, region, segment, > > * and page tables that do not make use of enhanced features like EDAT1. > > Thanks!