Message-ID: <7a1d0eb0-ab08-4fa8-bdab-b193b69a8c9d@sirena.org.uk>
Date: Fri, 3 Oct 2025 11:57:35 +0100
From: Mark Brown <broonie@...nel.org>
To: Deepanshu Kartikey <kartikey406@...il.com>
Cc: muchun.song@...ux.dev, osalvador@...e.de, david@...hat.com,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	syzbot+f26d7c75c26ec19790e7@...kaller.appspotmail.com,
	Aishwarya.TCV@....com
Subject: Re: [PATCH v2] hugetlbfs: skip VMAs without shareable locks in
 hugetlb_vmdelete_list

On Fri, Sep 26, 2025 at 09:02:54AM +0530, Deepanshu Kartikey wrote:
> hugetlb_vmdelete_list() uses trylock to acquire VMA locks during truncate
> operations. As per the original design in commit 40549ba8f8e0 ("hugetlb:
> use new vma_lock for pmd sharing synchronization"), if the trylock fails
> or the VMA has no lock, it should skip that VMA. Any remaining mapped
> pages are handled by remove_inode_hugepages() which is called after
> hugetlb_vmdelete_list() and uses proper lock ordering to guarantee
> unmapping success.

For the past few days I've been seeing failures on Raspberry Pi 4 in
the hugetlbfs-madvise kselftest in -next which bisect to this patch.
The test reports:

# # -------------------------
# # running ./hugetlb-madvise
# # -------------------------
# # Unexpected number of free huge pages line 252
# # [FAIL]
# not ok 6 hugetlb-madvise # exit=1

Full log:

  https://lava.sirena.org.uk/scheduler/job/1913276#L1803

Bisect log:

# bad: [7396732143a22b42bb97710173d598aaf50daa89] Add linux-next specific files for 20251002
# good: [9d3bc72cc0a9791bf4910ef854b2c3dd61af3bbf] Merge branch 'for-rc' of https://git.kernel.org/pub/scm/linux/kernel/git/fwctl/fwctl.git
# good: [d4ecae56a8c7d3287a5bcdb2d65f7102ee580ab6] clk: mediatek: Add MT8196 mcu clock support
# good: [4c134c2a5f3db29afe35b2d30e39bb6d867b08da] um: Indent time-travel help messages
# good: [bf1af4f6e62878e053d20cd71267aed8dfb3e715] perf arm-spe: Downsample all sample types equally
# good: [e414334883f4835058ca06f934bc4988eb9cd9e6] Merge branch 'next/dt' into for-next
# good: [54653bb3ec83d1f717adab6108db82a3966d19ee] clk: renesas: rzv2h: remove round_rate() in favor of determine_rate()
# good: [87a877de367d835b527d1086f75727123ef85fc4] KVM: x86: Rename handle_fastpath_set_msr_irqoff() to handle_fastpath_wrmsr()
# good: [c26675447faff8c4ddc1dc5d2cd28326b8181aaf] KVM: x86: Zero XSTATE components on INIT by iterating over supported features
# good: [6684aba0780da9f505c202f27e68ee6d18c0aa66] XArray: Add extra debugging check to xas_lock and friends
git bisect start '7396732143a22b42bb97710173d598aaf50daa89' '9d3bc72cc0a9791bf4910ef854b2c3dd61af3bbf' 'd4ecae56a8c7d3287a5bcdb2d65f7102ee580ab6' '4c134c2a5f3db29afe35b2d30e39bb6d867b08da' 'bf1af4f6e62878e053d20cd71267aed8dfb3e715' 'e414334883f4835058ca06f934bc4988eb9cd9e6' '54653bb3ec83d1f717adab6108db82a3966d19ee' '87a877de367d835b527d1086f75727123ef85fc4' 'c26675447faff8c4ddc1dc5d2cd28326b8181aaf' '6684aba0780da9f505c202f27e68ee6d18c0aa66'
# test job: [d4ecae56a8c7d3287a5bcdb2d65f7102ee580ab6] https://lava.sirena.org.uk/scheduler/job/1907306
# test job: [4c134c2a5f3db29afe35b2d30e39bb6d867b08da] https://lava.sirena.org.uk/scheduler/job/1903298
# test job: [bf1af4f6e62878e053d20cd71267aed8dfb3e715] https://lava.sirena.org.uk/scheduler/job/1900552
# test job: [e414334883f4835058ca06f934bc4988eb9cd9e6] https://lava.sirena.org.uk/scheduler/job/1904803
# test job: [54653bb3ec83d1f717adab6108db82a3966d19ee] https://lava.sirena.org.uk/scheduler/job/1900685
# test job: [87a877de367d835b527d1086f75727123ef85fc4] https://lava.sirena.org.uk/scheduler/job/1697972
# test job: [c26675447faff8c4ddc1dc5d2cd28326b8181aaf] https://lava.sirena.org.uk/scheduler/job/1698132
# test job: [6684aba0780da9f505c202f27e68ee6d18c0aa66] https://lava.sirena.org.uk/scheduler/job/1738722
# test job: [7396732143a22b42bb97710173d598aaf50daa89] https://lava.sirena.org.uk/scheduler/job/1913276
# bad: [7396732143a22b42bb97710173d598aaf50daa89] Add linux-next specific files for 20251002
git bisect bad 7396732143a22b42bb97710173d598aaf50daa89
# test job: [74fc450198cf792e3db35ea4d49197a467233373] https://lava.sirena.org.uk/scheduler/job/1913848
# bad: [74fc450198cf792e3db35ea4d49197a467233373] Merge branch 'main' of https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
git bisect bad 74fc450198cf792e3db35ea4d49197a467233373
# test job: [db484ff3fff1fafa0017cdd017795bec09ace5e4] https://lava.sirena.org.uk/scheduler/job/1913993
# bad: [db484ff3fff1fafa0017cdd017795bec09ace5e4] Merge branch 'docs-next' of git://git.lwn.net/linux.git
git bisect bad db484ff3fff1fafa0017cdd017795bec09ace5e4
# test job: [7d942c9d9660e6808dcd835c4c73ad5405cc5518] https://lava.sirena.org.uk/scheduler/job/1914055
# bad: [7d942c9d9660e6808dcd835c4c73ad5405cc5518] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git
git bisect bad 7d942c9d9660e6808dcd835c4c73ad5405cc5518
# test job: [db03d3c83bdb21667392d1596fafdfb38325c2a0] https://lava.sirena.org.uk/scheduler/job/1914176
# bad: [db03d3c83bdb21667392d1596fafdfb38325c2a0] Merge branch 'dma-mapping-for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux.git
git bisect bad db03d3c83bdb21667392d1596fafdfb38325c2a0
# test job: [84a7a9823e73fe3c0adcc4780fa7a091981048ef] https://lava.sirena.org.uk/scheduler/job/1914247
# good: [84a7a9823e73fe3c0adcc4780fa7a091981048ef] mm/shmem, swap: remove redundant error handling for replacing folio
git bisect good 84a7a9823e73fe3c0adcc4780fa7a091981048ef
# test job: [c7416f37e4d31fb28ac4ed584b13037e69a22dbe] https://lava.sirena.org.uk/scheduler/job/1914387
# bad: [c7416f37e4d31fb28ac4ed584b13037e69a22dbe] Merge branch 'mm-nonmm-stable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect bad c7416f37e4d31fb28ac4ed584b13037e69a22dbe
# test job: [3dfd02c900379d209ac9dcac24b4a61d8478842a] https://lava.sirena.org.uk/scheduler/job/1914497
# good: [3dfd02c900379d209ac9dcac24b4a61d8478842a] hugetlb: increase number of reserving hugepages via cmdline
git bisect good 3dfd02c900379d209ac9dcac24b4a61d8478842a
# test job: [fe7a283b39160153b6d1bd7f61b0a9d5d44987a8] https://lava.sirena.org.uk/scheduler/job/1915206
# good: [fe7a283b39160153b6d1bd7f61b0a9d5d44987a8] ocfs2: add suballoc slot check in ocfs2_validate_inode_block()
git bisect good fe7a283b39160153b6d1bd7f61b0a9d5d44987a8
# test job: [74058c0a9fc8b2b4d5f4a0ef7ee2cfa66a9e49cf] https://lava.sirena.org.uk/scheduler/job/1916011
# good: [74058c0a9fc8b2b4d5f4a0ef7ee2cfa66a9e49cf] Squashfs: fix uninit-value in squashfs_get_parent
git bisect good 74058c0a9fc8b2b4d5f4a0ef7ee2cfa66a9e49cf
# test job: [9f1c14c1de1bdde395f6cc893efa4f80a2ae3b2b] https://lava.sirena.org.uk/scheduler/job/1916064
# good: [9f1c14c1de1bdde395f6cc893efa4f80a2ae3b2b] Squashfs: reject negative file sizes in squashfs_read_inode()
git bisect good 9f1c14c1de1bdde395f6cc893efa4f80a2ae3b2b
# test job: [fb552b2425cf8f16c9c72229a972d1744b24d855] https://lava.sirena.org.uk/scheduler/job/1916102
# good: [fb552b2425cf8f16c9c72229a972d1744b24d855] alloc_tag: fix boot failure due to NULL pointer dereference
git bisect good fb552b2425cf8f16c9c72229a972d1744b24d855
# test job: [81e78b7ec61e89e8bab9736551839f79b063614c] https://lava.sirena.org.uk/scheduler/job/1916193
# bad: [81e78b7ec61e89e8bab9736551839f79b063614c] mm: convert folio_page() back to a macro
git bisect bad 81e78b7ec61e89e8bab9736551839f79b063614c
# test job: [1acc369373008b9eeb930fbb47847c0693055553] https://lava.sirena.org.uk/scheduler/job/1916218
# bad: [1acc369373008b9eeb930fbb47847c0693055553] mm/khugepaged: use start_addr/addr for improved readability
git bisect bad 1acc369373008b9eeb930fbb47847c0693055553
# test job: [dd83609b88986f4add37c0871c3434310652ebd5] https://lava.sirena.org.uk/scheduler/job/1916225
# bad: [dd83609b88986f4add37c0871c3434310652ebd5] hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list
git bisect bad dd83609b88986f4add37c0871c3434310652ebd5
# first bad commit: [dd83609b88986f4add37c0871c3434310652ebd5] hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list

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