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Wed, 1 Apr 2026 14:39:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775054391; bh=Bin3h0MVBuLpZNOozDl0N5IbBmgJsj/6z8avaWy2Ems=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Fq45RAyfqPyZhSNjubD5Vk0QTJAji108yWWmRtTHXhBeBGa6SNTNhSQfa/8ImIA5t PBbwVa0LSavhZMqUNLMp6HxVMCoN3UPaxbLk6lZn0HwvyQ2KyC95N9kTxeTLAHthg+ wVfMR2v0jA4jXxMDSar8TIz74Q8xSFRAil/h3g523HQ/JC0PhJxRGKAp3/Th2ocn7V zpWDIsOR/NH4nJhehVMK1x2osOI+N4vj4skpuO0lVLF6XOdeYs08ieKPBBA0VrfWXt YGu/Ao9/N00IOwjfDwDSTGmJNn3ZB4M7VSO6153nvheEa7+3Irz6X55p3gAO/kxNb7 VKjwk9lyc3CUg== Message-ID: <5684cab6-d5a6-4de9-9545-f8cae775d825@kernel.org> Date: Wed, 1 Apr 2026 16:39:45 +0200 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 11/13] selftests/mm: fix double increment in linked list cleanup in compaction_test To: Sayali Patil , Andrew Morton , Shuah Khan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Ritesh Harjani Cc: Zi Yan , Michal Hocko , Oscar Salvador , Lorenzo Stoakes , Dev Jain , Liam.Howlett@oracle.com, linuxppc-dev@lists.ozlabs.org, Venkat Rao Bagalkote References: <4c47a2ebbc41f90c7a0cb3f8b34106b2b64296f6.1774591179.git.sayalip@linux.ibm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 4/1/26 16:32, Sayali Patil wrote: > > On 27/03/26 12:46, Sayali Patil wrote: >> The cleanup loop of allocated memory currently uses: >> >>      for (entry = list; entry != NULL; entry = entry->next) { >>          munmap(entry->map, MAP_SIZE); >>          if (!entry->next) >>              break; >>          entry = entry->next; >>      } >> >> The inner entry = entry->next causes the loop to skip every >> other node, resulting in only half of the mapped regions being >> unmapped. >> >> Remove the redundant increment to ensure every entry is visited >> and unmapped during cleanup. >> >> Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory") >> Reviewed-by: Zi Yan >> Acked-by: David Hildenbrand (Arm) >> Tested-by: Venkat Rao Bagalkote >> Signed-off-by: Sayali Patil >> --- >>   tools/testing/selftests/mm/compaction_test.c | 3 --- >>   1 file changed, 3 deletions(-) >> >> diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/ >> testing/selftests/mm/compaction_test.c >> index 30209c40b697..f73930706bd0 100644 >> --- a/tools/testing/selftests/mm/compaction_test.c >> +++ b/tools/testing/selftests/mm/compaction_test.c >> @@ -263,9 +263,6 @@ int main(int argc, char **argv) >>         for (entry = list; entry != NULL; entry = entry->next) { >>           munmap(entry->map, MAP_SIZE); >> -        if (!entry->next) >> -            break; >> -        entry = entry->next; >>       } >>         if (check_compaction(mem_free, hugepage_size, > > Sorry, this change is not valid. > > The goal of this test is to verify the kernel’s ability to compact > unevictable (MAP_LOCKED) pages. The loop is intentionally written to > unmap every other chunk, thereby creating fragmentation with locked pages > before check_compaction() is invoked. > > With the proposed change (removing the double increment), the loop ends up > unmapping all allocated locked pages instead of leaving a fragmented > pattern. This results in memory being effectively unfragmented. Ahhh, we should really make that clearer in a comment. I missed it myself :( -- Cheers, David