From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7151E3F7878; Wed, 1 Jul 2026 08:49:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782895744; cv=none; b=dZzl8d+4ey1ahmy+Dk9yUPb8zo2/CBl3GXk5/oMiU3BwBIrSqbrqnMHZt5peLTY/DPOHdGkDOfOmR4GylX1WVCrbDIWQe+HvOyU+Rn49GfOiAtBAnzL016s1VGSMvRG8k3Z8Q1hHvhQW7g6lfiNeOxbhTTSvRawLBxDeKmz9csc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782895744; c=relaxed/simple; bh=LkAKnTOMehIMvtVkOh1qG3ojzRP5Y8KOGW+kP0hrKKQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KzbKw7Dn04S2ZDY1vcOfF41+9zfNy3Y2BWE4j+ooDtOCyrmE1uIxTZjRufb2ZKdt7228Ous/1bDQu337VKc73AjYTxRib9zi4KamH4a4elFmg3uI6MGFRe6CUERnDbFVhOjUk11AW1iGiX9JHPoo/xey0qLgGAZSP8dak7jieu0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UHHaODqK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UHHaODqK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C93CD1F00A3E; Wed, 1 Jul 2026 08:48:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782895741; bh=Qwh3iCvPoscNvLdWAClhJFPVit/GjXCDqMIF/PB2xCY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=UHHaODqKt/7I9kXLn5TRk/fGFrTWSf+1LZEkQYk+MTXMVHcxP82H+QCE1Q4eJRcV4 ASOoFiFBROJEEEqNF1rVfK9VdTGcwlgUdmZzWiXZoCqoEu1Wi6o36I5lzUkAywYgot t7axQEnnKW2HBT98BSGCa89fsvXVNaBwyuYW4znYMpISemm7MRb90bgvv1TxrRKBbM em+fjdvJ7SYMrdhRnFWhGQDCzNP3ZH5nLCIEXNtwn3N+65hIlCfXa9NmJc4GrCbl4K rGiwqMy6MYajD0EfCPwhZ+tNtN7YzoBE76wpWB6b+3JfTckZTOnz6L2ti/RA/UmALH mIoCtChly3Liw== Message-ID: <32a42e83-3e5e-4b00-b78c-d762094b9d76@kernel.org> Date: Wed, 1 Jul 2026 10:48:55 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] selftests/mm: handle EINVAL when configuring gigantic hugepages 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, Miaohe Lin , Venkat Rao Bagalkote References: <3d394c8cd59fe380d4e2d13b051544f241918f07.1782811071.git.sayalip@linux.ibm.com> <968b496a-a83e-491a-950c-3f6f975fa5f5@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 6/30/26 22:20, Sayali Patil wrote: > > > 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. We can either convert the functions to use flags, or hide it in some internal helpers, like the following: >From 1b1b8ad51f1f0be469cb191736300254b9521fe4 Mon Sep 17 00:00:00 2001 From: "David Hildenbrand (Arm)" Date: Wed, 1 Jul 2026 10:45:16 +0200 Subject: [PATCH] tmp Signed-off-by: David Hildenbrand (Arm) --- tools/testing/selftests/mm/vm_util.c | 28 ++++++++++++++++++++++++---- tools/testing/selftests/mm/vm_util.h | 1 + 2 files changed, 25 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c index 311fc5b4513eb..362070f817e9b 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -719,7 +719,8 @@ int read_file(const char *path, char *buf, size_t buflen) return (unsigned int) numread; } -void write_file(const char *path, const char *buf, size_t buflen) +static int __write_file(const char *path, const char *buf, size_t buflen, + bool ignore_einval) { int fd, saved_errno; ssize_t numwritten; @@ -735,14 +736,23 @@ void write_file(const char *path, const char *buf, size_t buflen) saved_errno = errno; close(fd); errno = saved_errno; - if (numwritten < 0) + + if (numwritten < 0) { + if (ignore_einval && errno == EINVAL) + return; ksft_exit_fail_msg("%s write(%.*s) failed: %s\n", path, (int)(buflen - 1), buf, strerror(errno)); + } if (numwritten != buflen - 1) ksft_exit_fail_msg("%s write(%.*s) is truncated, expected %zu bytes, got %zd bytes\n", path, (int)(buflen - 1), buf, buflen - 1, numwritten); } +static void write_file(const char *path, const char *buf, size_t buflen) +{ + __write_file(path, bug, buflen, /* ignore_einval = */ false); +} + unsigned long read_num(const char *path) { char buf[21]; @@ -753,12 +763,22 @@ unsigned long read_num(const char *path) return strtoul(buf, NULL, 10); } -void write_num(const char *path, unsigned long num) +static void __write_num(const char *path, unsigned long num, bool ignore_einval) { char buf[21]; sprintf(buf, "%lu", num); - write_file(path, buf, strlen(buf) + 1); + write_file(path, buf, strlen(buf) + 1, ignore_einval); +} + +void write_num(const char *path, unsigned long num) +{ + return __write_num(path, num, /* ignore_einval = */ false); +} + +void write_num_ignore_einval(const char *path, unsigned long num) +{ + return __write_num(path, num, /* ignore_einval = */ true); } static unsigned long shmall, shmmax; diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h index ea8fc8fdf0eb0..7799154b67eed 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -168,6 +168,7 @@ void write_file(const char *path, const char *buf, size_t buflen); int read_file(const char *path, char *buf, size_t buflen); unsigned long read_num(const char *path); void write_num(const char *path, unsigned long num); +void write_num_ignore_einval(const char *path, unsigned long num); void shm_limits_prepare(unsigned long length); void __shm_limits_restore(void); -- 2.43.0 -- Cheers, David