From: syzbot <syzbot+27727256237e6bdd3649@syzkaller.appspotmail.com>
To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Forwarded: Re: [syzbot] [fuse?] possible deadlock in __folio_end_writeback
Date: Wed, 26 Aug 2026 02:09:04 -0700 [thread overview]
Message-ID: <6a8ead30.a5a502ce.31d34.015a.GAE@google.com> (raw)
In-Reply-To: <68e583e1.a00a0220.298cc0.0485.GAE@google.com>
For archival purposes, forwarding an incoming command email to
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***
Subject: Re: [syzbot] [fuse?] possible deadlock in __folio_end_writeback
Author: miklos@szeredi.hu
#syz fix: flex_proportions: make fprop_new_period() hardirq safe
On Tue, 7 Oct 2025 at 23:19, syzbot
<syzbot+27727256237e6bdd3649@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: cbf33b8e0b36 Merge tag 'bpf-fixes' of git://git.kernel.org..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17a25ee2580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=1b4263e12240e6e1
> dashboard link: https://syzkaller.appspot.com/bug?extid=27727256237e6bdd3649
> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14eaea7c580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=134c4304580000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-cbf33b8e.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/54786e46ef23/vmlinux-cbf33b8e.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/dd6f88ce083b/bzImage-cbf33b8e.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+27727256237e6bdd3649@syzkaller.appspotmail.com
>
> wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
> wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
> =====================================================
> WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
> syzkaller #0 Not tainted
> -----------------------------------------------------
> kworker/u4:0/12 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
> ffffffff995aa110 (&p->sequence){+.-.}-{0:0}, at: __fprop_add_percpu_max+0x10d/0x210 lib/flex_proportions.c:186
>
> and this task is already holding:
> ffff888040a24240 (&xa->xa_lock#12){-...}-{3:3}, at: __folio_end_writeback+0x1da/0x950 mm/page-writeback.c:2996
> which would create a new lock dependency:
> (&xa->xa_lock#12){-...}-{3:3} -> (&p->sequence){+.-.}-{0:0}
>
> but this new dependency connects a HARDIRQ-irq-safe lock:
> (&xa->xa_lock#12){-...}-{3:3}
>
> ... which became HARDIRQ-irq-safe at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
> __folio_end_writeback+0x1da/0x950 mm/page-writeback.c:2996
> folio_end_writeback_no_dropbehind+0x151/0x290 mm/filemap.c:1668
> folio_end_writeback+0xea/0x220 mm/filemap.c:1694
> end_bio_bh_io_sync+0xba/0x120 fs/buffer.c:2776
> blk_update_request+0x57e/0xe60 block/blk-mq.c:998
> scsi_end_request+0x7c/0x830 drivers/scsi/scsi_lib.c:637
> scsi_io_completion+0x131/0x390 drivers/scsi/scsi_lib.c:1078
> ata_qc_complete_multiple+0x1ae/0x280 drivers/ata/libata-sata.c:789
> ahci_qc_complete drivers/ata/libahci.c:1887 [inline]
> ahci_handle_port_interrupt+0x3d5/0x610 drivers/ata/libahci.c:1954
> ahci_port_intr drivers/ata/libahci.c:1965 [inline]
> ahci_handle_port_intr+0x19f/0x2e0 drivers/ata/libahci.c:1996
> ahci_single_level_irq_intr+0x9b/0xe0 drivers/ata/libahci.c:2030
> __handle_irq_event_percpu+0x295/0xab0 kernel/irq/handle.c:203
> handle_irq_event_percpu kernel/irq/handle.c:240 [inline]
> handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:257
> handle_edge_irq+0x23b/0xa10 kernel/irq/chip.c:855
> generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
> handle_irq arch/x86/kernel/irq.c:254 [inline]
> call_irq_handler arch/x86/kernel/irq.c:-1 [inline]
> __common_interrupt+0x141/0x1f0 arch/x86/kernel/irq.c:325
> common_interrupt+0xb6/0xe0 arch/x86/kernel/irq.c:318
> asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
> __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
> _raw_spin_unlock_irqrestore+0xa8/0x110 kernel/locking/spinlock.c:194
> spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
> ata_scsi_queuecmd+0x3f0/0x5c0 drivers/ata/libata-scsi.c:4398
> scsi_dispatch_cmd drivers/scsi/scsi_lib.c:1626 [inline]
> scsi_queue_rq+0x1c91/0x2cc0 drivers/scsi/scsi_lib.c:1868
> blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2129
> __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
> blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
> __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
> blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
> blk_mq_run_hw_queue+0x404/0x4f0 block/blk-mq.c:2367
> blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
> blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2976
> __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225
> blk_finish_plug+0x5e/0x90 block/blk-core.c:1252
> wb_writeback+0xa80/0xaf0 fs/fs-writeback.c:2233
> wb_check_old_data_flush fs/fs-writeback.c:2301 [inline]
> wb_do_writeback fs/fs-writeback.c:2354 [inline]
> wb_workfn+0xaef/0xef0 fs/fs-writeback.c:2382
> process_one_work kernel/workqueue.c:3263 [inline]
> process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> to a HARDIRQ-irq-unsafe lock:
> (&p->sequence){+.-.}-{0:0}
>
> ... which became HARDIRQ-irq-unsafe at:
> ...
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x1a3/0x3a0 lib/flex_proportions.c:74
> writeout_period+0x8b/0x130 mm/page-writeback.c:615
> call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
> expire_timers kernel/time/timer.c:1798 [inline]
> __run_timers kernel/time/timer.c:2372 [inline]
> __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384
> run_timer_base kernel/time/timer.c:2393 [inline]
> run_timer_softirq+0x103/0x180 kernel/time/timer.c:2404
> handle_softirqs+0x283/0x870 kernel/softirq.c:622
> run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1063
> smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> other info that might help us debug this:
>
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&p->sequence);
> local_irq_disable();
> lock(&xa->xa_lock#12);
> lock(&p->sequence);
> <Interrupt>
> lock(&xa->xa_lock#12);
>
> *** DEADLOCK ***
>
> 5 locks held by kworker/u4:0/12:
> #0: ffff888030f92948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
> #0: ffff888030f92948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
> #1: ffffc900001e7bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
> #1: ffffc900001e7bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
> #2: ffff888000a240e0 (&type->s_umount_key#54){.+.+}-{4:4}, at: super_trylock_shared+0x20/0xf0 fs/super.c:562
> #3: ffff888040a24638 (&fi->lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
> #3: ffff888040a24638 (&fi->lock){+.+.}-{3:3}, at: fuse_writepages_send fs/fuse/file.c:2089 [inline]
> #3: ffff888040a24638 (&fi->lock){+.+.}-{3:3}, at: fuse_iomap_writeback_range+0x818/0x1800 fs/fuse/file.c:2150
> #4: ffff888040a24240 (&xa->xa_lock#12){-...}-{3:3}, at: __folio_end_writeback+0x1da/0x950 mm/page-writeback.c:2996
>
> the dependencies between HARDIRQ-irq-safe lock and the holding lock:
> -> (&xa->xa_lock#12){-...}-{3:3} {
> IN-HARDIRQ-W at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
> __folio_end_writeback+0x1da/0x950 mm/page-writeback.c:2996
> folio_end_writeback_no_dropbehind+0x151/0x290 mm/filemap.c:1668
> folio_end_writeback+0xea/0x220 mm/filemap.c:1694
> end_bio_bh_io_sync+0xba/0x120 fs/buffer.c:2776
> blk_update_request+0x57e/0xe60 block/blk-mq.c:998
> scsi_end_request+0x7c/0x830 drivers/scsi/scsi_lib.c:637
> scsi_io_completion+0x131/0x390 drivers/scsi/scsi_lib.c:1078
> ata_qc_complete_multiple+0x1ae/0x280 drivers/ata/libata-sata.c:789
> ahci_qc_complete drivers/ata/libahci.c:1887 [inline]
> ahci_handle_port_interrupt+0x3d5/0x610 drivers/ata/libahci.c:1954
> ahci_port_intr drivers/ata/libahci.c:1965 [inline]
> ahci_handle_port_intr+0x19f/0x2e0 drivers/ata/libahci.c:1996
> ahci_single_level_irq_intr+0x9b/0xe0 drivers/ata/libahci.c:2030
> __handle_irq_event_percpu+0x295/0xab0 kernel/irq/handle.c:203
> handle_irq_event_percpu kernel/irq/handle.c:240 [inline]
> handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:257
> handle_edge_irq+0x23b/0xa10 kernel/irq/chip.c:855
> generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
> handle_irq arch/x86/kernel/irq.c:254 [inline]
> call_irq_handler arch/x86/kernel/irq.c:-1 [inline]
> __common_interrupt+0x141/0x1f0 arch/x86/kernel/irq.c:325
> common_interrupt+0xb6/0xe0 arch/x86/kernel/irq.c:318
> asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
> __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
> _raw_spin_unlock_irqrestore+0xa8/0x110 kernel/locking/spinlock.c:194
> spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
> ata_scsi_queuecmd+0x3f0/0x5c0 drivers/ata/libata-scsi.c:4398
> scsi_dispatch_cmd drivers/scsi/scsi_lib.c:1626 [inline]
> scsi_queue_rq+0x1c91/0x2cc0 drivers/scsi/scsi_lib.c:1868
> blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2129
> __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
> blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
> __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
> blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
> blk_mq_run_hw_queue+0x404/0x4f0 block/blk-mq.c:2367
> blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
> blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2976
> __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225
> blk_finish_plug+0x5e/0x90 block/blk-core.c:1252
> wb_writeback+0xa80/0xaf0 fs/fs-writeback.c:2233
> wb_check_old_data_flush fs/fs-writeback.c:2301 [inline]
> wb_do_writeback fs/fs-writeback.c:2354 [inline]
> wb_workfn+0xaef/0xef0 fs/fs-writeback.c:2382
> process_one_work kernel/workqueue.c:3263 [inline]
> process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> INITIAL USE at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
> _raw_spin_lock_irq+0xa2/0xf0 kernel/locking/spinlock.c:170
> spin_lock_irq include/linux/spinlock.h:376 [inline]
> shmem_add_to_page_cache+0x72d/0xba0 mm/shmem.c:887
> shmem_alloc_and_add_folio+0x846/0xf60 mm/shmem.c:1936
> shmem_get_folio_gfp+0x59d/0x1660 mm/shmem.c:2533
> shmem_read_folio_gfp+0x8a/0xe0 mm/shmem.c:5931
> drm_gem_get_pages+0x223/0xa20 drivers/gpu/drm/drm_gem.c:656
> drm_gem_shmem_get_pages_locked+0x201/0x440 drivers/gpu/drm/drm_gem_shmem_helper.c:200
> drm_gem_shmem_pin_locked+0x22c/0x460 drivers/gpu/drm/drm_gem_shmem_helper.c:261
> drm_gem_shmem_vmap_locked+0x46b/0x790 drivers/gpu/drm/drm_gem_shmem_helper.c:365
> drm_gem_vmap_locked drivers/gpu/drm/drm_gem.c:1279 [inline]
> drm_gem_vmap+0x10a/0x1d0 drivers/gpu/drm/drm_gem.c:1321
> drm_client_buffer_vmap+0x43/0x80 drivers/gpu/drm/drm_client.c:312
> drm_fbdev_shmem_driver_fbdev_probe+0x258/0x900 drivers/gpu/drm/drm_fbdev_shmem.c:160
> drm_fb_helper_single_fb_probe drivers/gpu/drm/drm_fb_helper.c:1650 [inline]
> __drm_fb_helper_initial_config_and_unlock+0x1236/0x18a0 drivers/gpu/drm/drm_fb_helper.c:1830
> drm_fbdev_client_hotplug+0x16c/0x230 drivers/gpu/drm/clients/drm_fbdev_client.c:52
> drm_client_register+0x172/0x210 drivers/gpu/drm/drm_client.c:141
> drm_fbdev_client_setup+0x19f/0x3f0 drivers/gpu/drm/clients/drm_fbdev_client.c:159
> drm_client_setup+0x107/0x220 drivers/gpu/drm/clients/drm_client_setup.c:46
> vkms_create drivers/gpu/drm/vkms/vkms_drv.c:201 [inline]
> vkms_init+0x3e0/0x4b0 drivers/gpu/drm/vkms/vkms_drv.c:221
> do_one_initcall+0x233/0x820 init/main.c:1283
> do_initcall_level+0x104/0x190 init/main.c:1345
> do_initcalls+0x59/0xa0 init/main.c:1361
> kernel_init_freeable+0x334/0x4b0 init/main.c:1593
> kernel_init+0x1d/0x1d0 init/main.c:1483
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> }
> ... key at: [<ffffffff995cb060>] xa_init_flags.__key+0x0/0x20
>
> the dependencies between the lock to be acquired
> and HARDIRQ-irq-unsafe lock:
> -> (&p->sequence){+.-.}-{0:0} {
> HARDIRQ-ON-W at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x1a3/0x3a0 lib/flex_proportions.c:74
> writeout_period+0x8b/0x130 mm/page-writeback.c:615
> call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
> expire_timers kernel/time/timer.c:1798 [inline]
> __run_timers kernel/time/timer.c:2372 [inline]
> __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384
> run_timer_base kernel/time/timer.c:2393 [inline]
> run_timer_softirq+0x103/0x180 kernel/time/timer.c:2404
> handle_softirqs+0x283/0x870 kernel/softirq.c:622
> run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1063
> smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> IN-SOFTIRQ-W at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x1a3/0x3a0 lib/flex_proportions.c:74
> writeout_period+0x8b/0x130 mm/page-writeback.c:615
> call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
> expire_timers kernel/time/timer.c:1798 [inline]
> __run_timers kernel/time/timer.c:2372 [inline]
> __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384
> run_timer_base kernel/time/timer.c:2393 [inline]
> run_timer_softirq+0x103/0x180 kernel/time/timer.c:2404
> handle_softirqs+0x283/0x870 kernel/softirq.c:622
> run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1063
> smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> INITIAL USE at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x1a3/0x3a0 lib/flex_proportions.c:74
> writeout_period+0x8b/0x130 mm/page-writeback.c:615
> call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
> expire_timers kernel/time/timer.c:1798 [inline]
> __run_timers kernel/time/timer.c:2372 [inline]
> __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384
> run_timer_base kernel/time/timer.c:2393 [inline]
> run_timer_softirq+0x103/0x180 kernel/time/timer.c:2404
> handle_softirqs+0x283/0x870 kernel/softirq.c:622
> run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1063
> smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> INITIAL READ USE at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> seqcount_lockdep_reader_access include/linux/seqlock.h:72 [inline]
> fprop_fraction_percpu+0x170/0x400 lib/flex_proportions.c:155
> __wb_calc_thresh+0x119/0x4a0 mm/page-writeback.c:913
> wb_bg_dirty_limits mm/page-writeback.c:2130 [inline]
> domain_over_bg_thresh mm/page-writeback.c:2144 [inline]
> wb_over_bg_thresh+0x154/0x3d0 mm/page-writeback.c:2165
> wb_check_background_flush fs/fs-writeback.c:2257 [inline]
> wb_do_writeback fs/fs-writeback.c:2355 [inline]
> wb_workfn+0xb1c/0xef0 fs/fs-writeback.c:2382
> process_one_work kernel/workqueue.c:3263 [inline]
> process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> }
> ... key at: [<ffffffff99ac9760>] fprop_global_init.__key.1+0x0/0x20
> ... acquired at:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> seqcount_lockdep_reader_access include/linux/seqlock.h:72 [inline]
> fprop_fraction_percpu+0x130/0x400 lib/flex_proportions.c:155
> __fprop_add_percpu_max+0x10d/0x210 lib/flex_proportions.c:186
> wb_domain_writeout_add mm/page-writeback.c:562 [inline]
> __wb_writeout_add+0xa5/0x290 mm/page-writeback.c:586
> __folio_end_writeback+0x4d5/0x950 mm/page-writeback.c:3003
> folio_end_writeback_no_dropbehind+0x151/0x290 mm/filemap.c:1668
> folio_end_writeback+0xea/0x220 mm/filemap.c:1694
> fuse_writepage_finish fs/fuse/file.c:1837 [inline]
> fuse_send_writepage fs/fuse/file.c:1887 [inline]
> fuse_flush_writepages+0x6c8/0x900 fs/fuse/file.c:1912
> fuse_writepages_send fs/fuse/file.c:2091 [inline]
> fuse_iomap_writeback_range+0x923/0x1800 fs/fuse/file.c:2150
> iomap_writeback_range fs/iomap/buffered-io.c:1593 [inline]
> iomap_writeback_folio+0xe72/0x1c80 fs/iomap/buffered-io.c:1718
> iomap_writepages+0x162/0x2d0 fs/iomap/buffered-io.c:1770
> fuse_writepages+0x2ad/0x380 fs/fuse/file.c:2220
> do_writepages+0x32b/0x550 mm/page-writeback.c:2604
> __writeback_single_inode+0x145/0xff0 fs/fs-writeback.c:1719
> writeback_sb_inodes+0x6c7/0x1010 fs/fs-writeback.c:2015
> __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:2086
> wb_writeback+0x44f/0xaf0 fs/fs-writeback.c:2197
> wb_check_background_flush fs/fs-writeback.c:2267 [inline]
> wb_do_writeback fs/fs-writeback.c:2355 [inline]
> wb_workfn+0xb63/0xef0 fs/fs-writeback.c:2382
> process_one_work kernel/workqueue.c:3263 [inline]
> process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 12 Comm: kworker/u4:0 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> Workqueue: writeback wb_workfn (flush-0:42)
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_bad_irq_dependency kernel/locking/lockdep.c:2616 [inline]
> check_irq_usage kernel/locking/lockdep.c:2857 [inline]
> check_prev_add kernel/locking/lockdep.c:3169 [inline]
> check_prevs_add kernel/locking/lockdep.c:3284 [inline]
> validate_chain+0x1f05/0x2140 kernel/locking/lockdep.c:3908
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> seqcount_lockdep_reader_access include/linux/seqlock.h:72 [inline]
> fprop_fraction_percpu+0x130/0x400 lib/flex_proportions.c:155
> __fprop_add_percpu_max+0x10d/0x210 lib/flex_proportions.c:186
> wb_domain_writeout_add mm/page-writeback.c:562 [inline]
> __wb_writeout_add+0xa5/0x290 mm/page-writeback.c:586
> __folio_end_writeback+0x4d5/0x950 mm/page-writeback.c:3003
> folio_end_writeback_no_dropbehind+0x151/0x290 mm/filemap.c:1668
> folio_end_writeback+0xea/0x220 mm/filemap.c:1694
> fuse_writepage_finish fs/fuse/file.c:1837 [inline]
> fuse_send_writepage fs/fuse/file.c:1887 [inline]
> fuse_flush_writepages+0x6c8/0x900 fs/fuse/file.c:1912
> fuse_writepages_send fs/fuse/file.c:2091 [inline]
> fuse_iomap_writeback_range+0x923/0x1800 fs/fuse/file.c:2150
> iomap_writeback_range fs/iomap/buffered-io.c:1593 [inline]
> iomap_writeback_folio+0xe72/0x1c80 fs/iomap/buffered-io.c:1718
> iomap_writepages+0x162/0x2d0 fs/iomap/buffered-io.c:1770
> fuse_writepages+0x2ad/0x380 fs/fuse/file.c:2220
> do_writepages+0x32b/0x550 mm/page-writeback.c:2604
> __writeback_single_inode+0x145/0xff0 fs/fs-writeback.c:1719
> writeback_sb_inodes+0x6c7/0x1010 fs/fs-writeback.c:2015
> __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:2086
> wb_writeback+0x44f/0xaf0 fs/fs-writeback.c:2197
> wb_check_background_flush fs/fs-writeback.c:2267 [inline]
> wb_do_writeback fs/fs-writeback.c:2355 [inline]
> wb_workfn+0xb63/0xef0 fs/fs-writeback.c:2382
> process_one_work kernel/workqueue.c:3263 [inline]
> process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
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>
> If you want syzbot to run the reproducer, reply with:
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> If you attach or paste a git patch, syzbot will apply it before testing.
>
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prev parent reply other threads:[~2026-08-26 9:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-07 21:19 [syzbot] [fuse?] possible deadlock in __folio_end_writeback syzbot
2025-10-08 1:10 ` Hillf Danton
2025-10-08 1:32 ` syzbot
2025-10-09 8:55 ` Hillf Danton
2025-10-09 9:16 ` syzbot
2025-11-30 22:47 ` Tingmao Wang
2026-08-26 9:09 ` syzbot [this message]
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