linux-kernel - Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge pages to any order.

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Message-ID: <C18F1F9F-A4FC-4F37-9414-A7ED5233E913@nvidia.com>
Date: Mon, 04 Mar 2024 13:31:19 -0500
From: Zi Yan <ziy@...dia.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: "\"Pankaj Raghav (Samsung)\"" <kernel@...kajraghav.com>,
 linux-mm@...ck.org, "\"Matthew Wilcox (Oracle)\"" <willy@...radead.org>,
 David Hildenbrand <david@...hat.com>, Yang Shi <shy828301@...il.com>,
 Yu Zhao <yuzhao@...gle.com>,
 "\"Kirill A . Shutemov\"" <kirill.shutemov@...ux.intel.com>,
 Ryan Roberts <ryan.roberts@....com>,
 "Michal Koutný" <mkoutny@...e.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 "\"Zach O'Keefe\"" <zokeefe@...gle.com>, Hugh Dickins <hughd@...gle.com>,
 Luis Chamberlain <mcgrof@...nel.org>, linux-kernel@...r.kernel.org,
 cgroups@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Mark Brown <broonie@...nel.org>,
 Aishwarya TCV <aishwarya.tcv@....com>
Subject: Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge
 pages to any order.

On 4 Mar 2024, at 10:57, Zi Yan wrote:

> On 4 Mar 2024, at 10:44, Aishwarya TCV wrote:
>
>> On 04/03/2024 14:58, Zi Yan wrote:
>>> On 4 Mar 2024, at 4:50, Aishwarya TCV wrote:
>>>
>>>> On 01/03/2024 21:10, Zi Yan wrote:
>>>>> On 1 Mar 2024, at 15:02, Zi Yan wrote:
>>>>>
>>>>>> On 1 Mar 2024, at 14:37, Zi Yan wrote:
>>>>>>
>>>>>>> On 1 Mar 2024, at 4:51, Aishwarya TCV wrote:
>>>>>>>
>>>>>>>> On 26/02/2024 20:55, Zi Yan wrote:
>>>>>>>>> From: Zi Yan <ziy@...dia.com>
>>>>>>>>>
>>>>>>>>> It is used to test split_huge_page_to_list_to_order for pagecache THPs.
>>>>>>>>> Also add test cases for split_huge_page_to_list_to_order via both
>>>>>>>>> debugfs.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Zi Yan <ziy@...dia.com>
>>>>>>>>> ---
>>>>>>>>>  mm/huge_memory.c                              |  34 ++++--
>>>>>>>>>  .../selftests/mm/split_huge_page_test.c       | 115 +++++++++++++++++-
>>>>>>>>>  2 files changed, 131 insertions(+), 18 deletions(-)
>>>>>>>>>
>>>>>>>>
>>>>>>>> Hi Zi,
>>>>>>>>
>>>>>>>> When booting the kernel against next-master(20240228)with Arm64 on
>>>>>>>> Marvell Thunder X2 (TX2), the kselftest-mm test 'split_huge_page_test'
>>>>>>>> is failing in our CI (with rootfs over NFS). I can send the full logs if
>>>>>>>> required.
>>>>>>>>
>>>>>>>> A bisect (full log below) identified this patch as introducing the
>>>>>>>> failure. Bisected it on the tag "next-20240228" at repo
>>>>>>>> "https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git".
>>>>>>>>
>>>>>>>> This works fine on  Linux version 6.8.0-rc6
>>>>>>>
>>>>>>> Hi Aishwarya,
>>>>>>>
>>>>>>> Can you try the attached patch and see if it fixes the failure? I changed
>>>>>>> the test to accept XFS dev as input, mount XFS on a temp folder under /tmp,
>>>>>>> and skip if no XFS is mounted.
>>>>>>
>>>>>> Please try this updated one. It allows you to specify a XFS device path
>>>>>> in SPLIT_HUGE_PAGE_TEST_XFS_PATH env variable, which is passed to
>>>>>> split_huge_page_test in run_vmtests.sh. It at least allow CI/CD to run
>>>>>> the test without too much change.
>>>>>
>>>>> OK. This hopefully will be my last churn. Now split_huge_page_test accepts
>>>>> a path that is backed by XFS and run_vmtest.sh creates a XFS image in /tmp,
>>>>> mounts it in /tmp, and gives the path to split_huge_page_test. I tested
>>>>> it locally and it works. Let me know if you have any issue. Thanks.
>>>>>
>>>>> --
>>>>> Best Regards,
>>>>> Yan, Zi
>>>>
>>>> Hi Zi,
>>>>
>>>> Tested the patch by applying it on next-20240304. Logs from our CI with
>>>> rootfs over nfs is attached below. "Bail out! cannot remove tmp dir:
>>>> Directory not empty" is still observed.
>>>
>>> Hi Aishwarya,
>>>
>>> Do you have the config file for the CI kernel? And /tmp is also on nfs?
>>> Any detailed information about CI machine environment? I cannot reproduce
>>> the error locally, either on bare metal or VM. Maybe because my /tmp is
>>> not NFS mounted?
>>>
>>
>> Hi Zi,
>>
>> Please find the details below. Hope it helps.
>>
>> Do you have the config file for the CI kernel?
>> - We are using:
>> defconfig+https://github.com/torvalds/linux/blob/master/tools/testing/selftests/mm/config
>>
>> And /tmp is also on nfs?
>> - Yes
>>
>> Any detailed information about CI machine environment?
>> - We are running the test using LAVA device Cavium Thunder X2 (TX2),
>> - We have very similar rootfs as - nfsrootfs:
>> https://storage.kernelci.org/images/rootfs/debian/bullseye-kselftest/20240129.0/arm64/full.rootfs.tar.xz
>> - We are using grub boot method over nfs
>> - Additionally Ryan mentioned "Looks like it is failing because he is
>> trying to delete the temp dir with rmdir() but rmdir() requires the
>> directory to be empty, which it is not."
>
> Hi Aishwarya,
>
> Thank you for the information and I am able to reproduce it on a NFS folder.
> The error comes from that the opened test files are not munmapped and their
> file descriptors are not closed in the skip path. NFS creates .nfsXXX files
> for them, making the temp folder not empty.
>
> The attached patch cleans up properly and works on a NFS folder. Let me know
> if it works on your side. Thanks.

Hi Andrew,

Could you fold the patch from [1] to this one (i.e., Patch 8)? Let me know
if you want me to send it separately or resend the entire patchset. Thanks.

[1] https://lore.kernel.org/linux-mm/57259BE4-D4A1-4F57-8AEA-DE526C43DE44@nvidia.com/

--
Best Regards,
Yan, Zi

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