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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id x7-20020a259a07000000b00b8f6ec5a955sm1266497ybn.49.2023.05.21.22.22.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 May 2023 22:22:16 -0700 (PDT) Date: Sun, 21 May 2023 22:22:13 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: 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 , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 25/31] mm/gup: remove FOLL_SPLIT_PMD use of pmd_trans_unstable() In-Reply-To: <68a97fbe-5c1e-7ac6-72c-7b9c6290b370@google.com> Message-ID: References: <68a97fbe-5c1e-7ac6-72c-7b9c6290b370@google.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" There is now no reason for follow_pmd_mask()'s FOLL_SPLIT_PMD block to distinguish huge_zero_page from a normal THP: follow_page_pte() handles any instability, and here it's a good idea to replace any pmd_none(*pmd) by a page table a.s.a.p, in the huge_zero_page case as for a normal THP. (Hmm, couldn't the normal THP case have hit an unstably refaulted THP before? But there are only two, exceptional, users of FOLL_SPLIT_PMD.) Signed-off-by: Hugh Dickins --- mm/gup.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index bb67193c5460..4ad50a59897f 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -681,21 +681,10 @@ static struct page *follow_pmd_mask(struct vm_area_st= ruct *vma, return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); } if (flags & FOLL_SPLIT_PMD) { - int ret; - page =3D pmd_page(*pmd); - if (is_huge_zero_page(page)) { - spin_unlock(ptl); - ret =3D 0; - split_huge_pmd(vma, pmd, address); - if (pmd_trans_unstable(pmd)) - ret =3D -EBUSY; - } else { - spin_unlock(ptl); - split_huge_pmd(vma, pmd, address); - ret =3D pte_alloc(mm, pmd) ? -ENOMEM : 0; - } - - return ret ? ERR_PTR(ret) : + spin_unlock(ptl); + split_huge_pmd(vma, pmd, address); + /* If pmd was left empty, stuff a page table in there quickly */ + return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) : follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); } page =3D follow_trans_huge_pmd(vma, address, pmd, flags); --=20 2.35.3