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b=Mojc1X2e2BKYS5x6as8pQ1NzXmlundxvuGcBb5WPkaE7dvY7/dEEGUKy/DPS9i95v UIJesHTcAlIJTjtw/Oyk9SMcyAu9quYuxtqUg2e3bcSRFPkxa27VTOGMKge/ni2P5V jWFk9wmBeHYwcu4pjSffNF+67ayFWIYsEAcg9aL1Vll9RW+5laPjhtGkphDbsYoxWQ HLefio5ZpWeUHpBqFDJanj6jK9AY1G4+Ci4BwjEgiVLquuoFoGn/D9l9dMMXnW8pKk na+ra7w5ODe3CkjBBXKvkCNQm11V8ndON9dKEZzD5YFdhlUDCUsAVgRuUMkgEHyO3Q blAaGAUvPdDng== Message-ID: <226ec797-ff8c-4465-a682-21c684a25021@kernel.org> Date: Fri, 25 Sep 2026 09:41:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] selftests/mm: add a test for UFFDIO_MOVE of a write-protected swap entry To: Donggeun Yoo , akpm@linux-foundation.org, rppt@kernel.org Cc: peterx@redhat.com, surenb@google.com, aarcange@redhat.com, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, mhocko@suse.com, shuah@kernel.org, kirill@shutemov.name, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260925042907.2330519-1-donggeunyoo.kernel@gmail.com> <20260925042907.2330519-3-donggeunyoo.kernel@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: ihet83tuonnqexeswzo3ngmwsqt5zo55 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 3409420004 X-HE-Tag: 1790322092-563201 X-HE-Meta: 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 Z1gOPoRf qQQ1uDMn7lNzTdXxVQZs9ZGkQmKOTfvDFw+7YNT3Rkld2b69NtOnhCHZuu0jJ8Z4OYYRpWhMD39XebArggpHptSRerIq2lPEQiuAiw0/E+QlL2CFSABdxSzghLUa6dVhs70oYcKhByluEvVeyYgQKuUJzzM6rlg5k5gccyoUQngQC7AYTCvCY9dOifxRtSt5oq5f0oqJOXC7ti4v0egtjN6dxBvCt+gyGxIcka0cOtatmSuNbFaH2oONx/VMCKY9is4wXWk1/C+xDr4kqyqoq/VULJzetO+BM446nHRY+vxKpP+jcU/lVv30Ajf3xoseswQ9BJh7tReLipAM18tc/oHfnlFDXj5NMhuHUZ0hZN1Hk6cumPz7UOXF2CizpFO7e0YBhR1y/yJiBNPYHOoiLMg8IWbimddmAzB4WLX/WozVw1/3YcWQ2aDDGVw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/25/26 06:29, Donggeun Yoo wrote: > Move a swapped-out page out of a write-protected area into a destination > registered for missing faults only, and read pagemap bit 57 at the > destination. The destination was never write-protected, so the bit must > be clear. > > Assisted-by: LLM > Signed-off-by: Donggeun Yoo > --- > tools/testing/selftests/mm/uffd-unit-tests.c | 61 ++++++++++++++++++++ > 1 file changed, 61 insertions(+) > > diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c > index ef9b3956bdcfd..ae8b718f0a278 100644 > --- a/tools/testing/selftests/mm/uffd-unit-tests.c > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c > @@ -2037,6 +2037,59 @@ static void uffd_move_pmd_split_test(uffd_global_test_opts_t *gopts, uffd_test_a > uffd_move_pmd_handle_fault); > } > > +/* > + * Moving a swapped-out page out of a write-protected area must not carry the > + * uffd-wp bit into a destination that is not write-protect registered: such a > + * bit is never cleared afterwards, so pagemap keeps reporting the page as > + * uffd-tracked. > + * > + * Needs a swap device; skipped if MADV_PAGEOUT cannot evict the page. > + */ > +static void uffd_move_swap_wp_test(uffd_global_test_opts_t *gopts, > + uffd_test_args_t *targs) > +{ > + unsigned long page_size = gopts->page_size; > + struct uffdio_move move = { }; > + int pagemap_fd, i; > + > + if (uffd_register(gopts->uffd, gopts->area_src, page_size, > + false, true, false)) > + err("register src failure"); > + if (uffd_register(gopts->uffd, gopts->area_dst, page_size, > + true, false, false)) Side note: this binary encoding of features is horrible. > + err("register dst failure"); > + > + wp_range(gopts->uffd, (unsigned long)gopts->area_src, page_size, true); > + > + pagemap_fd = pagemap_open(); > + for (i = 0; i < 100; i++) { > + if (madvise(gopts->area_src, page_size, MADV_PAGEOUT)) > + err("MADV_PAGEOUT"); > + if (pagemap_is_swapped(pagemap_fd, gopts->area_src)) > + break; > + usleep(10000); > + } Is this loop really required? I thought the page should just be unmapped from the page table. It might still be in the swapcache and under writeback, but that's irrelevant. > + if (!pagemap_is_swapped(pagemap_fd, gopts->area_src)) { > + uffd_test_skip("MADV_PAGEOUT did not swap the page; is swap enabled?"); > + goto out; > + } > + > + move.dst = (unsigned long)gopts->area_dst; > + move.src = (unsigned long)gopts->area_src; > + move.len = page_size; > + if (ioctl(gopts->uffd, UFFDIO_MOVE, &move)) > + err("UFFDIO_MOVE"); > + > + if (pagemap_get_entry(pagemap_fd, gopts->area_dst) & PM_UFFD_WP) > + uffd_test_fail("uffd-wp bit moved into an area that is not write-protected"); > + else > + uffd_test_pass(); > +out: > + close(pagemap_fd); > + uffd_unregister(gopts->uffd, gopts->area_src, page_size); > + uffd_unregister(gopts->uffd, gopts->area_dst, page_size); > +} > + > static bool > uffdio_verify_results(const char *name, int ret, int error, long result) > { > @@ -2359,6 +2412,14 @@ uffd_test_case_t uffd_tests[] = { > .uffd_feature_required = UFFD_FEATURE_MOVE, > .test_case_ops = &uffd_move_test_pmd_case_ops, > }, > + { > + .name = "move-swap-wp", > + .uffd_fn = uffd_move_swap_wp_test, > + .mem_targets = MEM_ANON, > + .uffd_feature_required = UFFD_FEATURE_MOVE | > + UFFD_FEATURE_PAGEFAULT_FLAG_WP, > + .test_case_ops = &uffd_move_test_case_ops, > + }, Do we also want to check wrp? I'd assume it suffers from the same problem (did not check carefully though) -- Cheers, David