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[70.52.229.124]) by smtp.gmail.com with ESMTPSA id f17-20020a05620a281100b00748676d89e7sm1253297qkp.8.2023.04.14.07.10.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Apr 2023 07:10:01 -0700 (PDT) Date: Fri, 14 Apr 2023 10:09:59 -0400 From: Peter Xu To: Mika =?utf-8?B?UGVudHRpbMOk?= Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Axel Rasmussen , Andrew Morton , David Hildenbrand , Mike Kravetz , Nadav Amit , Andrea Arcangeli , linux-stable Subject: Re: [PATCH 1/6] mm/hugetlb: Fix uffd-wp during fork() Message-ID: References: <20230413231120.544685-1-peterx@redhat.com> <20230413231120.544685-2-peterx@redhat.com> <9cb84b60-6b51-3117-27cb-a29b3bd9e741@mbosol.com> MIME-Version: 1.0 In-Reply-To: <9cb84b60-6b51-3117-27cb-a29b3bd9e741@mbosol.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 48f9w93ako11opazn9smyjr8kfuijfcs X-Rspamd-Queue-Id: 9C6A980039 X-HE-Tag: 1681481406-461979 X-HE-Meta: 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 ciOXilo1 TXl5PjcLABHMbq54prjH0b5OXWRPihtbhbBtptK53usnshmtL2rH0Z3T6/HNWcmYcDFTZ+j7mJoksdnADhoFqbf9MLEeGoObEidUruif/LRRV6vDqQQ6ePjjp5Fyox7FRxyvxGnvdjNmibx5skuDddFuymQPVPQAV1gv8Qvxji3wLqdRzEatqQ3o35l0/XuMxhe9d2fOVmpvM+hwgwRHVtmB8IzqKrICctTGVeEt8yv5PafDZFw6D4UK+H6uwI2i2UPpy3YeCAZvsxPiAQnyaYSfyb1E3ODTghnSXvbqoqxS3lsms6mG+hTZGz+m64ieUedHBhPgAKi+vEg1AEOKDMSwDJMfj/3Gw0Rpm8k4CbzBBM/HfFJqIJxr256SLeHt/t0UVPGSjrjLPk2yKh/0djIK/zIyRQeE2eZfX0Fuq5Jx50YwjX2l6qzwu6COo+vYKzeIcrF9/gYlPXHk= 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 Fri, Apr 14, 2023 at 12:45:29PM +0300, Mika Penttilä wrote: > > } else if (unlikely(is_hugetlb_entry_migration(entry))) { > > swp_entry_t swp_entry = pte_to_swp_entry(entry); > > - bool uffd_wp = huge_pte_uffd_wp(entry); [1] > > if (!is_readable_migration_entry(swp_entry) && cow) { > > /* > > @@ -5049,11 +5050,12 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, > > swp_entry = make_readable_migration_entry( > > swp_offset(swp_entry)); > > entry = swp_entry_to_pte(swp_entry); [2] > > - if (userfaultfd_wp(src_vma) && uffd_wp) > > - entry = huge_pte_mkuffd_wp(entry); > > + if (userfaultfd_wp(src_vma) && > > + pte_swp_uffd_wp(entry)) > > + entry = pte_swp_mkuffd_wp(entry); > > > This looks interesting with pte_swp_uffd_wp and pte_swp_mkuffd_wp ? Could you explain what do you mean? I think these helpers are the right ones to use, as afaict hugetlb migration should follow the same pte format with !hugetlb. However, I noticed I did it wrong when dropping the temp var - when at [1], "entry" still points to the src entry, but at [2] it's already pointing to the newly created one.. so I think I can't drop the var, a fixup should like: ===8<=== diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 083aae35bff8..cd3a9d8f4b70 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5041,6 +5041,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, set_huge_pte_at(dst, addr, dst_pte, entry); } else if (unlikely(is_hugetlb_entry_migration(entry))) { swp_entry_t swp_entry = pte_to_swp_entry(entry); + bool uffd_wp = pte_swp_uffd_wp(entry); if (!is_readable_migration_entry(swp_entry) && cow) { /* @@ -5050,8 +5051,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, swp_entry = make_readable_migration_entry( swp_offset(swp_entry)); entry = swp_entry_to_pte(swp_entry); - if (userfaultfd_wp(src_vma) && - pte_swp_uffd_wp(entry)) + if (userfaultfd_wp(src_vma) && uffd_wp) entry = pte_swp_mkuffd_wp(entry); set_huge_pte_at(src, addr, src_pte, entry); ===8<=== Besides, did I miss something else? Thanks, -- Peter Xu