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U2FsdGVkX18iH5kvtLyEekQrqm93goecTyJV7HpqpmgC7QYjCisFMUzl6sTMdR3vIOtp4iIwVSeTd6YNy9nkiIGMV7Nb6XeMtQMJcTMvLL50s/dL5VmCb761eiw1x9sfUK7fd7LgwFg0T/msU9fBLR5JPc1B4rK54TE7nrGdMFmizuRYnWxJzDa+Hzp/6AQfip8wDPUGXzxHcAbU1lOHC2jpYIrTC6AYiWVwTM6b587olgR4YVH4zKTKzJLz2bYlw7is6cSQ5yT5g4Bcqe4i+HWxTBw9VQqvC+q9y7O3gZPpFF/OXpos3Rkl7pPp9Ry8aViBkg0HhBWfaJLiYL9s6pexiuaYgQjhGtAGyPuOXYkRtDDI0ppgu1aAsAaEWtZD8yqeoX/Vo8C8ze/fjHNvgrk34Cv/s0erkdcxqpMIQQ0mRoM6vt+eNHJ8uv/cl4FesSaj7pvi+WVGjjtLTaDHXwXII8V6Zl3G+wOyiUZbUX0rnzIvlzQmoixsaD7ZC8ghbXaVKvhnKnjMtTn2hMImStmVfcgpnR/qsnoBhy3dP4G+uAIM2bLQfZwykuf2DPXscNHLVxRSCc4LocqDWuaxgpmxftIYd7xJ3T3E9ZYe9lFlieuHFtOKUkZfgj+5MeEjEwdMk3A2ia6NtpY0c6hUdSENCqbxft0U913KByEzo4oGiHAEiCHirzVPhMekyg/Kb8eCygGb0oG8kGI842gRyAEGlwB+R1kVYS9G9eR1hJLBoZXYgrfYlRx5KC9NEz+J6mfo8Kjikqs+keiAPhYqOaY5/7YzXFlVKF2OLOtjTutwkD3e5SZ0suIX6jY0HZn9AviWvdAbB1rDaMlmEjZstrHj2oK/VHp17CpvF2V1TudXWH+6pYLKL0Ra4Su4W7DSTOA1bOTB85AlzJsnD05K77PU7zhz7GnLsXjf5d1Dw7RRI7Aqdbi+zT7Q48mHi62+Yt8c9u6lD1ILBGKzfId kg/2zOAD 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 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: List-Subscribe: List-Unsubscribe: On 1 Sep 2025, at 3:22, David Hildenbrand wrote: > On 31.08.25 04:27, Wei Yang wrote: > > Subject: "selftests/mm: verify page content after remapping PMD through= PTEs" > >> After mremap(), add a check on content to see whether mremap corrupt >> data. >> >> Signed-off-by: Wei Yang >> >> --- >> v2: add check on content instead of just test backed folio > > I'm confused, don't we have that exact check later in the function? > > Your v1 might have been better, unless I am missing something. > >> --- >> tools/testing/selftests/mm/split_huge_page_test.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools= /testing/selftests/mm/split_huge_page_test.c >> index 10ae65ea032f..229b6dcabece 100644 >> --- a/tools/testing/selftests/mm/split_huge_page_test.c >> +++ b/tools/testing/selftests/mm/split_huge_page_test.c >> @@ -423,10 +423,14 @@ static void split_pte_mapped_thp(void) >> /* smap does not show THPs after mremap, use kpageflags instead */= >> thp_size =3D 0; >> - for (i =3D 0; i < pagesize * 4; i++) >> + for (i =3D 0; i < pagesize * 4; i++) { >> + if (pte_mapped[i] !=3D (char)i) >> + ksft_exit_fail_msg("%ld byte corrupted\n", i); >> + >> if (i % pagesize =3D=3D 0 && >> is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpag= eflags_fd)) >> thp_size++; >> + } >> if (thp_size !=3D 4) >> ksft_exit_fail_msg("Some THPs are missing during mremap\n"); > > I'm a bit confused with this test in general. > > We do a > > pte_mapped =3D mremap(one_page, pagesize, pagesize, MREMAP_MAYMOVE); > > which I read as a "NOP". > > Questions > > (a) Will this actually do anything? Also, maybe it does now, but can't = the kernel just optimize that out in the future? It remaps each subpage of 4 PMD THPs into a contiguous 2MB vaddr range an= d perform split on that range. > > (b) Is it even guaranteed that we can access > pagesize afterwards? I m= ean, we specify MREMAP_MAYMOVE. > > > I would suggest to just use mprotect/madvise to pte-map a PMD-THP. If you want to test that, please add your own test case. -- Best Regards, Yan, Zi