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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 From: "zhangpeng (AS)" Subject: Re: [PATCH v2 0/3] userfaultfd: convert userfaultfd functions to use folios To: Matthew Wilcox CC: , , , , , , , References: <20230314131350.924377-1-zhangpeng362@huawei.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.160] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm600020.china.huawei.com (7.193.23.147) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 6421640009 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: yh6woxrk6x58sfer9i81memkgunmnkmq X-HE-Tag: 1679543094-210533 X-HE-Meta: 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 /KkQz1Z7 JGDWkdAv9kH/ToHNE/s5XhenCLNVaA1Ghx6zt28zBSXb/U8ni+tlZL7D8Ma4qoEbR73BiymRjF1POyXN1uf6SzvT6yLPGJgRyiaF9valVRW6rADPQDPUH5yDQk8ujJeoBHihghOCNqmCGVpxTs4uDCakbWeT59dkgrIlSA41oeuobsU8TFjFGoDc6V/FB06WIcx7vwtFevZgubNI9av4DHN5AOJTNU1HKIptX1nULTvTAbyln7/TKZowxhpbzQFweYeXywY0AmLQfTbv2bjPdD6+3Jc5einQS0GITgF4aH+rDEMM= 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 2023/3/14 21:23, Matthew Wilcox wrote: > On Tue, Mar 14, 2023 at 01:13:47PM +0000, Peng Zhang wrote: >> From: ZhangPeng >> >> This patch series converts several userfaultfd functions to use folios. >> And this series pass the userfaultfd selftests and the LTP userfaultfd >> test cases. > That's what you said about the earlier patchset too. Assuming you > ran the tests, they need to be improved to fid the bug that was in the > earlier version of the patches. I did run the tests both times before sending the patches. However, the bug in the earlier version patches[1] is a hard corner case[2] to trigger. To trigger it, we need to call copy_large_folio_from_user() with allow_pagefault == true, which requires hugetlb_mcopy_atomic_pte() to return -ENOENT. This means that calling copy_large_folio_from_user() with allow_pagefault == false failed, i.e. copy_from_user() failed. Building a self-test that copy_from_user() fails could be difficult. __mcopy_atomic() __mcopy_atomic_hugetlb() hugetlb_mcopy_atomic_pte() copy_large_folio_from_user(..., ..., false); // if ret_val > 0, return -ENOENT copy_from_user() // copy_from_user() needs to fail if (err == -ENOENT) copy_large_folio_from_user(..., ..., true); [1] https://lore.kernel.org/all/20230314033734.481904-3-zhangpeng362@huawei.com/ > -long copy_huge_page_from_user(struct page *dst_page, > +long copy_large_folio_from_user(struct folio *dst_folio, > const void __user *usr_src, > - unsigned int pages_per_huge_page, > bool allow_pagefault) > { > void *page_kaddr; > unsigned long i, rc = 0; > - unsigned long ret_val = pages_per_huge_page * PAGE_SIZE; > + unsigned int nr_pages = folio_nr_pages(dst_folio); > + unsigned long ret_val = nr_pages * PAGE_SIZE; > struct page *subpage; > + struct folio *inner_folio; > > - for (i = 0; i < pages_per_huge_page; i++) { > - subpage = nth_page(dst_page, i); > + for (i = 0; i < nr_pages; i++) { > + subpage = folio_page(dst_folio, i); > + inner_folio = page_folio(subpage); > if (allow_pagefault) > - page_kaddr = kmap(subpage); > + page_kaddr = kmap_local_folio(inner_folio, 0); > else > page_kaddr = kmap_atomic(subpage); > rc = copy_from_user(page_kaddr, > usr_src + i * PAGE_SIZE, PAGE_SIZE); > if (allow_pagefault) > - kunmap(subpage); > + kunmap_local(page_kaddr); > else > kunmap_atomic(page_kaddr); Thanks, Peng.