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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93c2474fbb3sm319077785a.6.2026.09.23.14.31.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 14:32:00 -0700 (PDT) Date: Wed, 23 Sep 2026 17:31:58 -0400 From: Gregory Price To: Yeoreum Yun Cc: Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , Shuah Khan Subject: Re: [PATCH v3 1/2] kselftest: mm: return fail when child test result is fail in khugepaged Message-ID: References: <20260923-fix_khugepagd_fail-v3-0-b387e92fe1a9@arm.com> <20260923-fix_khugepagd_fail-v3-1-b387e92fe1a9@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260923-fix_khugepagd_fail-v3-1-b387e92fe1a9@arm.com> X-Stat-Signature: 1goafxrdf64sdcoswta9skzn3dbd1wjo X-Rspamd-Queue-Id: 8A1608000A X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1790199121-767672 X-HE-Meta: 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 howDuQN+ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 23, 2026 at 04:29:51PM +0100, Yeoreum Yun wrote: > Although the child process in collapse_fork*() or collapse_max_ptes_shared() > reports `KSFT_FAIL`, the result is ignored because the test only checks > whether the parent’s page was collapsed into a huge page. > > As a result, the test is considered successful whenever the parent’s page > is a huge page, even if the child test fails, as shown below: > > # > # Run test: collapse_max_ptes_shared (khugepaged:anon) > # Allocate huge page... OK > # Share huge page over fork()... OK > # Trigger CoW on page 1023 of 2048... OK > # Maybe collapse with max_ptes_shared exceeded.... OK > # Trigger CoW on page 1024 of 2048... Fail > Bail out! Unexpected huge page > # Planned tests != run tests (26 != 23) > # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 // child failed. > # Check if parent still has huge page... OK // parent hpage success > ok 24 collapse_max_ptes_shared // considered as success > ... > # Totals: pass:26 fail:0 xfail:0 xpass:0 skip:0 error:0 > > To address this, propagate the child’s failure and skip the subsequent > check in the parent. > > Reviewed-by: Baolin Wang > Signed-off-by: Yeoreum Yun Reviewed-by: Gregory Price (Meta)