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Tue, 30 Jun 2026 20:20:48 +0000 (GMT) Received: from [9.124.209.216] (unknown [9.124.209.216]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 30 Jun 2026 20:20:48 +0000 (GMT) Message-ID: <968b496a-a83e-491a-950c-3f6f975fa5f5@linux.ibm.com> Date: Wed, 1 Jul 2026 01:50:46 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Sayali Patil Subject: Re: [PATCH v2 1/3] selftests/mm: handle EINVAL when configuring gigantic hugepages To: "David Hildenbrand (Arm)" , 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, Miaohe Lin , Venkat Rao Bagalkote References: <3d394c8cd59fe380d4e2d13b051544f241918f07.1782811071.git.sayalip@linux.ibm.com> Content-Language: en-IN In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: xyESTlO6dMLM7YcVtcvMAvaTwyluwrzX X-Proofpoint-Spam-Info: AW1haW4tMjYwNjMwMDE5NiBTYWx0ZWRfXwYC8CEf3+t4o KiyjGor5a04mKsKTRf7jX4eo4mzRJu2/C7NwJEzG02V/mIlZGyLO4Qi7Kj5lxnkISK5P++UhwT+ ImE/iurNuaTVuSm4F8y1I58k5E1Kufg= X-Authority-Analysis: v=2.4 cv=edsNubEH c=1 sm=1 tr=0 ts=6a442528 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=m02x96YjSDSQiHbJXYIA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjMwMDE5NiBTYWx0ZWRfX5RrnGuMnjta0 gdd5dAniw1EU9+cmYHg8yNafFjUwPFREIMD0JCAkW8PXv6mivlwxvxmMIx0RBLpUgYzMGWL8fa3 3xvHbVtDMhYVr3AaEaow9hRPgC90b4Sub4ohZ7NmV7aLdh6SPuGLvPXVZ2j/JOJ5hBWx584AtIm nbfJoWdjjU/NFStaOj6WTxrfaHpvFa/H6M6EEB1x25vfBvgclmS/LNObzZilaf6wM4yv69gUSgA p5CZwQmyK52eUx0bRylexxEzEflIKRVz5fPBj5hr6j2uQifJfzk54/zlgyI6ORs5nkU8YJ9ZylN hsjti6jc1NtOX3jcbezDJEz2UylY+u/RXOifrm66ykPMy4htd8MwAp4ZLr/j5reiLCLhDYA0n12 TRTphxp5I71/EYRWBtWYLSd9kBmmLmpe6NvMwFI/r5ZZUZlxgXgJBWbn7YbXYct2CIGpwBrtnod VLh+aHeglV0Cij6yYcQ== X-Proofpoint-ORIG-GUID: PqQIfZCw_cvbMYTbclLmQsh_ECd9ocEH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-30_05,2026-06-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 adultscore=0 impostorscore=0 bulkscore=0 spamscore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606300196 On 30/06/26 16:15, David Hildenbrand (Arm) wrote: > On 6/30/26 11:32, Sayali Patil wrote: >> Some MM selftests attempt to configure the amount of >> HugeTLB pages of different sizes by writing to nr_hugepages. >> >> PowerPC hash MMU pSeries systems advertise gigantic hugepage sizes >> but do not support runtime allocation of such pages, writes >> to the corresponding nr_hugepages file fail with -EINVAL. >> This causes the test to bail out even though the failure is due >> to a platform limitation rather than the >> functionality being tested. >> >> Treat -EINVAL from the sysfs write as a skipped configuration request >> and continue running the test instead of failing. >> >> Before patch: >> ------------------------- >> running ./hugetlb-madvise >> ------------------------- >> TAP version 13 >> 1..1 >> [INFO] detected hugetlb page size: 16777216 KiB >> [INFO] detected hugetlb page size: 16384 KiB >> ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb >> Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 >> Bail out! /sys/kernel/mm/hugepages/hugepages-16777216kB/nr_hugepages >> write(0) failed: Invalid argument >> Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 >> [FAIL] >> >> After patch: >> ------------------------- >> running ./hugetlb-madvise >> ------------------------- >> TAP version 13 >> 1..1 >> [INFO] detected hugetlb page size: 16777216 KiB >> [INFO] detected hugetlb page size: 16384 KiB >> ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb >> Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 >> /sys/kernel/mm/hugepages/hugepages-16777216kB/nr_hugepages >> write(0) failed: Invalid argument >> [PASS] >> >> Fixes: 27477b28b74f ("selftests/mm: hugepage_settings: add APIs to get and set nr_hugepages") >> Signed-off-by: Sayali Patil >> --- >> .../testing/selftests/mm/hugepage_settings.c | 32 ++++++++++++++++++- >> .../testing/selftests/mm/hugepage_settings.h | 1 + >> 2 files changed, 32 insertions(+), 1 deletion(-) >> >> diff --git a/tools/testing/selftests/mm/hugepage_settings.c b/tools/testing/selftests/mm/hugepage_settings.c >> index 2eab2110ac6a..ce38ae3da01a 100644 >> --- a/tools/testing/selftests/mm/hugepage_settings.c >> +++ b/tools/testing/selftests/mm/hugepage_settings.c >> @@ -422,6 +422,36 @@ static void hugetlb_sysfs_path(char *buf, size_t buflen, >> size / 1024, attr); >> } >> >> +void hugetlb_write_num(const char *path, unsigned long num) >> +{ >> + int fd, saved_errno; >> + ssize_t numwritten; >> + char buf[21]; >> + >> + sprintf(buf, "%lu", num); >> + >> + fd = open(path, O_WRONLY); >> + if (fd == -1) >> + ksft_exit_fail_msg("%s open failed: %s\n", path, strerror(errno)); >> + >> + numwritten = write(fd, buf, strlen(buf)); >> + saved_errno = errno; >> + close(fd); >> + errno = saved_errno; >> + >> + /* Treat EINVAL as a skipped configuration (e.g., unsupported gigantic pages) */ >> + if (numwritten < 0 && errno == EINVAL) { >> + ksft_print_msg("%s write(%s) failed: %s\n", path, buf, strerror(errno)); > > Should we even print anything here? Rather confusing. It's just like we cannot > allocate anything (no memory). > > In general, you are copy-pasting a lot of write_num()+write_file() content, > which is really suboptimal. > > All you want is an option for write_num -> write_file to skip on -EINVAL, correct? > > There are not that many write_num / write_file users ... > Hi David, Yes, all I need is to ignore the expected -EINVAL when attempting to configure gigantic hugepages via nr_hugepages. I looked at extending write_num()/write_file() for this as in v1 (https://lore.kernel.org/all/8bfa921e30eb94072685103f6496784aa23bb166.1782365671.git.sayalip@linux.ibm.com/), but these helpers are shared by several other selftests. For example, write_file() is used by split_huge_page_test setup and by khugepaged tests for drop_caches, and is also used for various THP and khugepaged settings where -EINVAL would indicate a genuine setup failure. This concern was also raised during the v1 review. Because the expected -EINVAL is specific to gigantic hugepage runtime allocation, I kept the handling local to the hugetlb setup path rather than changing the semantics of the common helpers. I also agree that printing a message is not particularly useful in this case, and we can simply return without emitting any output. Please let me know if you would prefer a different approach. Thanks, Sayali