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Wed, 26 Aug 2026 02:09:04 -0700 In-Reply-To: <68e583e1.a00a0220.298cc0.0485.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a8ead30.a5a502ce.31d34.015a.GAE@google.com> Subject: Forwarded: Re: [syzbot] [fuse?] possible deadlock in __folio_end_writeback From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** 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 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); > > 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: [] 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: [] 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: > > 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 > > > > --- > 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: > #syz fix: exact-commit-title > > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup