linux-kernel - Re: 6.15-rc1/regression/bisected - commit 474f7825d533 is broke systemd-nspawn on my system

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Message-ID: <20250407-unmodern-abkam-ce0395573fc2@brauner>
Date: Mon, 7 Apr 2025 16:15:24 +0200
From: Christian Brauner <brauner@...nel.org>
To: Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
Cc: sforshee@...nel.org, linux-fsdevel@...r.kernel.org, 
	Linux List Kernel Mailing <linux-kernel@...r.kernel.org>, Linux regressions mailing list <regressions@...ts.linux.dev>, 
	lennart@...ttering.net
Subject: Re: 6.15-rc1/regression/bisected - commit 474f7825d533 is broke
 systemd-nspawn on my system

On Mon, Apr 07, 2025 at 12:14:01PM +0500, Mikhail Gavrilov wrote:
> Hi,
> I use Fedora. On Fedora systemd-nspawn is used for creating a clean
> build environment for packaging.
> I noted that on fresh kernels I can't build packages any more because
> the command "mock -r fedora-rawhide-i386 --rebuild" is stuck.
> I started debugging and found that systemd-nspawn was hanging.
> Sending SysRq for  displaying list of blocked (D state) tasks gave me
> this trace:
> [  743.382717] sysrq: Show Blocked State
> [  743.383154] task:systemd-nspawn  state:D stack:27120 pid:4609
> tgid:4609  ppid:4435   task_flags:0x400140 flags:0x00000002
> [  743.383164] Call Trace:
> [  743.383167]  <TASK>
> [  743.383171]  __schedule+0x895/0x1bf0
> [  743.383178]  ? __pfx___schedule+0x10/0x10
> [  743.383182]  ? __pfx_do_raw_spin_trylock+0x10/0x10
> [  743.383187]  ? __raw_spin_unlock_irqrestore+0x5d/0x80
> [  743.383191]  ? rcu_is_watching+0x12/0xc0
> [  743.383195]  ? schedule+0x1d5/0x260
> [  743.383199]  schedule+0xd4/0x260
> [  743.383202]  fuse_get_req+0x92d/0x1060 [fuse]
> [  743.383218]  ? rcu_is_watching+0x12/0xc0
> [  743.383222]  ? __pfx_fuse_get_req+0x10/0x10 [fuse]
> [  743.383233]  ? rcu_is_watching+0x12/0xc0
> [  743.383236]  ? __pfx_autoremove_wake_function+0x10/0x10
> [  743.383240]  ? rcu_is_watching+0x12/0xc0
> [  743.383243]  ? is_bpf_text_address+0x64/0x100
> [  743.383247]  ? __pfx_stack_trace_consume_entry+0x10/0x10
> [  743.383252]  __fuse_simple_request+0x8f/0xab0 [fuse]
> [  743.383263]  ? kernel_text_address+0x145/0x160
> [  743.383268]  ? __kernel_text_address+0x12/0x40
> [  743.383272]  fuse_getxattr+0x2cd/0x3e0 [fuse]
> [  743.383287]  ? __pfx_fuse_getxattr+0x10/0x10 [fuse]
> [  743.383299]  ? rcu_is_watching+0x12/0xc0
> [  743.383304]  ? rcu_is_watching+0x12/0xc0
> [  743.383307]  ? is_bpf_text_address+0x64/0x100
> [  743.383310]  ? lock_release+0xb7/0xf0
> [  743.383314]  ? is_bpf_text_address+0x6e/0x100
> [  743.383318]  ? kernel_text_address+0x145/0x160
> [  743.383323]  fuse_xattr_get+0x64/0x90 [fuse]
> [  743.383333]  __vfs_getxattr+0xf0/0x150
> [  743.383338]  ? __pfx___vfs_getxattr+0x10/0x10
> [  743.383344]  get_vfs_caps_from_disk+0x138/0x450
> [  743.383349]  ? __pfx_get_vfs_caps_from_disk+0x10/0x10
> [  743.383353]  ? rcu_is_watching+0x12/0xc0
> [  743.383356]  ? handle_path+0x27c/0x6b0
> [  743.383360]  ? lock_release+0xb7/0xf0
> [  743.383363]  ? handle_path+0x281/0x6b0
> [  743.383368]  audit_copy_inode+0x339/0x4f0
> [  743.383372]  ? __pfx_audit_copy_inode+0x10/0x10
> [  743.383376]  ? path_lookupat+0x16a/0x670
> [  743.383381]  filename_lookup+0x391/0x550
> [  743.383386]  ? __pfx_filename_lookup+0x10/0x10
> [  743.383394]  ? audit_alloc_name+0x398/0x490
> [  743.383398]  ? __audit_getname+0x10b/0x160
> [  743.383402]  ? getname_flags.part.0+0x1a5/0x510
> [  743.383406]  user_path_at+0x9e/0xe0
> [  743.383411]  __x64_sys_mount_setattr+0x247/0x340
> [  743.383415]  ? __pfx___x64_sys_mount_setattr+0x10/0x10
> [  743.383418]  ? seqcount_lockdep_reader_access.constprop.0+0xa5/0xb0
> [  743.383422]  ? seqcount_lockdep_reader_access.constprop.0+0xa5/0xb0
> [  743.383426]  ? ktime_get_coarse_real_ts64+0x41/0xd0
> [  743.383431]  do_syscall_64+0x97/0x190
> [  743.383437]  ? rcu_is_watching+0x12/0xc0
> [  743.383440]  ? rcu_read_unlock+0x17/0x60
> [  743.383444]  ? lock_release+0xb7/0xf0
> [  743.383448]  ? handle_mm_fault+0x4e5/0xa60
> [  743.383451]  ? exc_page_fault+0x7e/0x110
> [  743.383456]  ? rcu_is_watching+0x12/0xc0
> [  743.383458]  ? exc_page_fault+0x7e/0x110
> [  743.383462]  ? do_user_addr_fault+0x8cb/0xe70
> [  743.383466]  ? irqentry_exit_to_user_mode+0xa2/0x290
> [  743.383469]  ? rcu_is_watching+0x12/0xc0
> [  743.383472]  ? irqentry_exit_to_user_mode+0xa2/0x290
> [  743.383475]  ? trace_hardirqs_on_prepare+0xdf/0x120
> [  743.383480]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> [  743.383483] RIP: 0033:0x7fac4ff0419e
> [  743.383499] RSP: 002b:00007ffc843092f8 EFLAGS: 00000246 ORIG_RAX:
> 00000000000001ba
> [  743.383504] RAX: ffffffffffffffda RBX: 000000000000000b RCX: 00007fac4ff0419e
> [  743.383507] RDX: 0000000000009000 RSI: 00007fac503472a8 RDI: 000000000000000b
> [  743.383509] RBP: 00007ffc843093a0 R08: 0000000000000020 R09: 00007fac4fff6ac0
> [  743.383512] R10: 00007ffc84309340 R11: 0000000000000246 R12: 0000000000000009
> [  743.383514] R13: 000056069822b629 R14: 000056069822b635 R15: 0000000000000007
> [  743.383519]  </TASK>
> 
> > sudo /usr/bin/systemd-nspawn -q --ephemeral -D /var/lib/mock/fedora-rawhide-x86_64/root
> [sudo] password for mikhail:
> ^CShort read while reading whether to enable FUSE.
> mikhail@...mary-ws ~ [1]>
> 
> And started bisecting the issue and the first bad commit is
> 474f7825d5335798742b92f067e1d22365013107.
> 
> Author: Christian Brauner <brauner@...nel.org>
> Date:   Tue Jan 28 11:33:40 2025 +0100
> 
>     fs: add copy_mount_setattr() helper
> 
>     Split out copy_mount_setattr() from mount_setattr() so we can use it in
>     later patches.
> 
>     Link: https://lore.kernel.org/r/20250128-work-mnt_idmap-update-v2-v1-2-c25feb0d2eb3@kernel.org
>     Reviewed-by: "Seth Forshee (DigitalOcean)" <sforshee@...nel.org>
>     Signed-off-by: Christian Brauner <brauner@...nel.org>
> 
> Unfortunately I can't test the revert of this commit because of conflicts.
> 
> > git revert -n 474f7825d5335798742b92f067e1d22365013107
> Auto-merging fs/namespace.c
> CONFLICT (content): Merge conflict in fs/namespace.c
> error: could not revert 474f7825d533... fs: add copy_mount_setattr() helper
> hint: after resolving the conflicts, mark the corrected paths
> hint: with 'git add <paths>' or 'git rm <paths>'
> hint: Disable this message with "git config set advice.mergeConflict false"
> 
> My machine spec: https://linux-hardware.org/?probe=619658e7cf
> And I attached below my build config and full kernel log.
> 
> Christian, can you look please?

I'm a bit confused by your git bisect log and the dmesg output you're
showing. The dmesg output suggests you did actually test on:

[    0.000000] Linux version 6.15.0-rc1 (mikhail@...mary-ws) (gcc (GCC) 14.2.1 20241104 (Red Hat 14.2.1-6), GNU ld version 2.44-3.fc43) #4 SMP PREEMPT_DYNAMIC Mon Apr  7 10:58:22 +05 2025

But your git bisect starts at 1a9239bb4253f9076b5b4b2a1a4e8d7defd77a95
according to:

git bisect start
# status: waiting for both good and bad commits
# bad: [1a9239bb4253f9076b5b4b2a1a4e8d7defd77a95] Merge tag 'net-next-6.15' of git://git.kernel.
git bisect bad 1a9239bb4253f9076b5b4b2a1a4e8d7defd77a95

Which is way before -rc1. Where you testing on actual v6.15-rc1 released
yesterday or were you testing on
1a9239bb4253f9076b5b4b2a1a4e8d7defd77a95? If the latter, please test
actual v6.15-rc1 as I suspect this is caused by faulty locking in
clone_private_mount() which I fixed.