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e9e14a558f8ab-3d3048803e7mr74610025ab.18.1740555550966; Tue, 25 Feb 2025 23:39:10 -0800 (PST) Date: Tue, 25 Feb 2025 23:39:10 -0800 In-Reply-To: <66f97d9a.050a0220.6bad9.001d.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <67bec51e.050a0220.2eba0.007d.GAE@google.com> Subject: Re: [syzbot] Re: [syzbot] [bcachefs?] possible deadlock in pcpu_alloc_noprof 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] [bcachefs?] possible deadlock in pcpu_alloc_noprof Author: mmpgouride@gmail.com > On Feb 12, 2025, at 12:31, syzbot wrote: > > syzbot has found a reproducer for the following issue on: > > HEAD commit: 09fbf3d50205 Merge tag 'tomoyo-pr-20250211' of git://git.c.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=14370aa4580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3c2347dd6174fbe2 > dashboard link: https://syzkaller.appspot.com/bug?extid=fe63f377148a6371a9db > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17404718580000 > > Downloadable assets: > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-09fbf3d5.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/835b3d29c46c/vmlinux-09fbf3d5.xz > kernel image: https://storage.googleapis.com/syzbot-assets/ff4bfd8a5d42/bzImage-09fbf3d5.xz > mounted in repro #1: https://storage.googleapis.com/syzbot-assets/24d046ee591e/mount_7.gz > mounted in repro #2: https://storage.googleapis.com/syzbot-assets/fc8a49472f19/mount_9.gz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+fe63f377148a6371a9db@syzkaller.appspotmail.com > > bcachefs (loop0): initializing new filesystem > bcachefs (loop0): going read-write > bcachefs (loop0): marking superblocks > ====================================================== > WARNING: possible circular locking dependency detected > 6.14.0-rc2-syzkaller-00039-g09fbf3d50205 #0 Not tainted > ------------------------------------------------------ > syz.0.21/5625 is trying to acquire lock: > ffffffff8ea19608 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x293/0x1760 mm/percpu.c:1782 > > but task is already holding lock: > ffff888051401c68 (&bc->lock){+.+.}-{4:4}, at: bch2_btree_node_mem_alloc+0x559/0x16f0 fs/bcachefs/btree_cache.c:804 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #2 (&bc->lock){+.+.}-{4:4}: > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851 > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730 > bch2_btree_cache_scan+0x184/0xec0 fs/bcachefs/btree_cache.c:482 > do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437 > shrink_slab+0x1093/0x14d0 mm/shrinker.c:664 > shrink_one+0x43b/0x850 mm/vmscan.c:4868 > shrink_many mm/vmscan.c:4929 [inline] > lru_gen_shrink_node mm/vmscan.c:5007 [inline] > shrink_node+0x37c5/0x3e50 mm/vmscan.c:5978 > kswapd_shrink_node mm/vmscan.c:6807 [inline] > balance_pgdat mm/vmscan.c:6999 [inline] > kswapd+0x20f3/0x3b10 mm/vmscan.c:7264 > kthread+0x7a9/0x920 kernel/kthread.c:464 > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > -> #1 (fs_reclaim){+.+.}-{0:0}: > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851 > __fs_reclaim_acquire mm/page_alloc.c:3853 [inline] > fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3867 > might_alloc include/linux/sched/mm.h:318 [inline] > slab_pre_alloc_hook mm/slub.c:4066 [inline] > slab_alloc_node mm/slub.c:4144 [inline] > __do_kmalloc_node mm/slub.c:4293 [inline] > __kmalloc_noprof+0xae/0x4c0 mm/slub.c:4306 > kmalloc_noprof include/linux/slab.h:905 [inline] > kzalloc_noprof include/linux/slab.h:1037 [inline] > pcpu_mem_zalloc mm/percpu.c:510 [inline] > pcpu_alloc_chunk mm/percpu.c:1430 [inline] > pcpu_create_chunk+0x57/0xbc0 mm/percpu-vm.c:338 > pcpu_balance_populated mm/percpu.c:2063 [inline] > pcpu_balance_workfn+0xc4d/0xd40 mm/percpu.c:2200 > process_one_work kernel/workqueue.c:3236 [inline] > process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317 > worker_thread+0x870/0xd30 kernel/workqueue.c:3398 > kthread+0x7a9/0x920 kernel/kthread.c:464 > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > -> #0 (pcpu_alloc_mutex){+.+.}-{4:4}: > check_prev_add kernel/locking/lockdep.c:3163 [inline] > check_prevs_add kernel/locking/lockdep.c:3282 [inline] > validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906 > __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228 > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851 > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730 > pcpu_alloc_noprof+0x293/0x1760 mm/percpu.c:1782 > __six_lock_init+0x104/0x150 fs/bcachefs/six.c:876 > bch2_btree_lock_init+0x38/0x100 fs/bcachefs/btree_locking.c:12 > bch2_btree_node_mem_alloc+0x565/0x16f0 fs/bcachefs/btree_cache.c:807 > __bch2_btree_node_alloc fs/bcachefs/btree_update_interior.c:304 [inline] > bch2_btree_reserve_get+0x2df/0x1890 fs/bcachefs/btree_update_interior.c:532 > bch2_btree_update_start+0xe56/0x14e0 fs/bcachefs/btree_update_interior.c:1230 > bch2_btree_split_leaf+0x121/0x880 fs/bcachefs/btree_update_interior.c:1851 > bch2_trans_commit_error+0x212/0x1380 fs/bcachefs/btree_trans_commit.c:908 > __bch2_trans_commit+0x812b/0x97a0 fs/bcachefs/btree_trans_commit.c:1085 > bch2_trans_commit fs/bcachefs/btree_update.h:183 [inline] > bch2_trans_mark_metadata_bucket+0x47a/0x17b0 fs/bcachefs/buckets.c:1043 > bch2_trans_mark_metadata_sectors fs/bcachefs/buckets.c:1060 [inline] > __bch2_trans_mark_dev_sb fs/bcachefs/buckets.c:1100 [inline] > bch2_trans_mark_dev_sb+0x3f6/0x820 fs/bcachefs/buckets.c:1128 > bch2_trans_mark_dev_sbs_flags+0x6be/0x720 fs/bcachefs/buckets.c:1138 > bch2_fs_initialize+0xba0/0x1610 fs/bcachefs/recovery.c:1149 > bch2_fs_start+0x36d/0x610 fs/bcachefs/super.c:1042 > bch2_fs_get_tree+0xd8d/0x1740 fs/bcachefs/fs.c:2203 > vfs_get_tree+0x90/0x2b0 fs/super.c:1814 > do_new_mount+0x2be/0xb40 fs/namespace.c:3560 > do_mount fs/namespace.c:3900 [inline] > __do_sys_mount fs/namespace.c:4111 [inline] > __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > other info that might help us debug this: > > Chain exists of: > pcpu_alloc_mutex --> fs_reclaim --> &bc->lock > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&bc->lock); > lock(fs_reclaim); > lock(&bc->lock); > lock(pcpu_alloc_mutex); > > *** DEADLOCK *** > > 4 locks held by syz.0.21/5625: > #0: ffff888051400278 (&c->state_lock){+.+.}-{4:4}, at: bch2_fs_start+0x45/0x610 fs/bcachefs/super.c:1010 > #1: ffff888051404378 (&c->btree_trans_barrier){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:164 [inline] > #1: ffff888051404378 (&c->btree_trans_barrier){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:256 [inline] > #1: ffff888051404378 (&c->btree_trans_barrier){.+.+}-{0:0}, at: __bch2_trans_get+0x7e4/0xd30 fs/bcachefs/btree_iter.c:3377 > #2: ffff8880514266d0 (&c->gc_lock){.+.+}-{4:4}, at: bch2_btree_update_start+0x682/0x14e0 fs/bcachefs/btree_update_interior.c:1180 > #3: ffff888051401c68 (&bc->lock){+.+.}-{4:4}, at: bch2_btree_node_mem_alloc+0x559/0x16f0 fs/bcachefs/btree_cache.c:804 > > stack backtrace: > CPU: 0 UID: 0 PID: 5625 Comm: syz.0.21 Not tainted 6.14.0-rc2-syzkaller-00039-g09fbf3d50205 #0 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 > Call Trace: > > __dump_stack lib/dump_stack.c:94 [inline] > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 > print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2076 > check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2208 > check_prev_add kernel/locking/lockdep.c:3163 [inline] > check_prevs_add kernel/locking/lockdep.c:3282 [inline] > validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906 > __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228 > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851 > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730 > pcpu_alloc_noprof+0x293/0x1760 mm/percpu.c:1782 > __six_lock_init+0x104/0x150 fs/bcachefs/six.c:876 > bch2_btree_lock_init+0x38/0x100 fs/bcachefs/btree_locking.c:12 > bch2_btree_node_mem_alloc+0x565/0x16f0 fs/bcachefs/btree_cache.c:807 > __bch2_btree_node_alloc fs/bcachefs/btree_update_interior.c:304 [inline] > bch2_btree_reserve_get+0x2df/0x1890 fs/bcachefs/btree_update_interior.c:532 > bch2_btree_update_start+0xe56/0x14e0 fs/bcachefs/btree_update_interior.c:1230 > bch2_btree_split_leaf+0x121/0x880 fs/bcachefs/btree_update_interior.c:1851 > bch2_trans_commit_error+0x212/0x1380 fs/bcachefs/btree_trans_commit.c:908 > __bch2_trans_commit+0x812b/0x97a0 fs/bcachefs/btree_trans_commit.c:1085 > bch2_trans_commit fs/bcachefs/btree_update.h:183 [inline] > bch2_trans_mark_metadata_bucket+0x47a/0x17b0 fs/bcachefs/buckets.c:1043 > bch2_trans_mark_metadata_sectors fs/bcachefs/buckets.c:1060 [inline] > __bch2_trans_mark_dev_sb fs/bcachefs/buckets.c:1100 [inline] > bch2_trans_mark_dev_sb+0x3f6/0x820 fs/bcachefs/buckets.c:1128 > bch2_trans_mark_dev_sbs_flags+0x6be/0x720 fs/bcachefs/buckets.c:1138 > bch2_fs_initialize+0xba0/0x1610 fs/bcachefs/recovery.c:1149 > bch2_fs_start+0x36d/0x610 fs/bcachefs/super.c:1042 > bch2_fs_get_tree+0xd8d/0x1740 fs/bcachefs/fs.c:2203 > vfs_get_tree+0x90/0x2b0 fs/super.c:1814 > do_new_mount+0x2be/0xb40 fs/namespace.c:3560 > do_mount fs/namespace.c:3900 [inline] > __do_sys_mount fs/namespace.c:4111 [inline] > __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7fcaed38e58a > Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007fcaec5fde68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 00007fcaec5fdef0 RCX: 00007fcaed38e58a > RDX: 00004000000000c0 RSI: 0000400000000180 RDI: 00007fcaec5fdeb0 > RBP: 00004000000000c0 R08: 00007fcaec5fdef0 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000400000000180 > R13: 00007fcaec5fdeb0 R14: 0000000000005a05 R15: 0000400000000480 > > bcachefs (loop0): initializing freespace > bcachefs (loop0): done initializing freespace > bcachefs (loop0): reading snapshots table > bcachefs (loop0): reading snapshots done > bcachefs (loop0): done starting filesystem > > > --- > 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. > #syz test: https://github.com/alanskind/bcachefs 42f41ed6bd37189a0a2dd9957d9aa1950cb8e1ea