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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id t202-20020a8183d3000000b005619cfb1b88sm306230ywf.52.2023.06.08.18.40.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jun 2023 18:40:03 -0700 (PDT) Date: Thu, 8 Jun 2023 18:39:59 -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 , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 25/32] mm/gup: remove FOLL_SPLIT_PMD use of pmd_trans_unstable() In-Reply-To: Message-ID: <59fd15dd-4d39-5ec-2043-1d5117f7f85@google.com> References: 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; and this removes an unnecessary possibility of -EBUSY failure. (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 Reviewed-by: Yang Shi --- 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