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smtpav03.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 8 Jul 2026 07:01:31 +0000 (GMT) Message-ID: <198eac9f-3b77-4376-8ae6-9c0ae13d60cd@linux.ibm.com> Date: Wed, 8 Jul 2026 12:31:30 +0530 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> <968b496a-a83e-491a-950c-3f6f975fa5f5@linux.ibm.com> <32a42e83-3e5e-4b00-b78c-d762094b9d76@kernel.org> Content-Language: en-IN In-Reply-To: <32a42e83-3e5e-4b00-b78c-d762094b9d76@kernel.org> Content-Type: text/plain; charset=UTF-8; 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X-HE-Meta: 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 NLlJz6Bz +7rsO0epPk2r5aDVcCkjQUy46pteSTEuKwGD2faTAGmAbCD9dyObMuyIZm3Tsfze5HWk9sr84LOx54/1/a2aknD89IuFKe/MN0HhGk59sNYojRcShPH8YBuGlRvYJv8pn84afylA/sbiEdLx1xoDfhhJqYN7+zgKLcGcpzIjwHlx6aWsh3+GUO6USl36mlI2huoAlb/WI07kd2+ckZ4qpZ47wNNwAIg2nHCvwUrvwdah/Jf4YBPSuMHdW+eH7GwAMwxd6CnksSmVjxxCK5nq7qr/4BF8siSIHErlIs+8dj+P8lmQuxBZyvJgl3nqljEpr+6uxCV0uV+nlFxc1GVqwYPUxGSBuwF+3D4zyZ1iZgS7oB+kHZpVcfLIPIsCqdDwb9rS3/EHIeQ1ld7NUVKnmipeaGn+ct213Ppy3XnQfpjbAWENdrYvj4yqgD2HH1fDEoI6yOn5HZpZd0mjguqcb/N+egw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 01/07/26 14:18, David Hildenbrand (Arm) wrote: > 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); Thanks, David. I've sent out v3 incorporating the suggested changes. V3:https://lore.kernel.org/all/cover.1783446924.git.sayalip@linux.ibm.com/