On my f2fs USB stick used as ccache cache I get the following crash – so far only when compiling Chromium and apparently always at the same file. fsck.f2fs (from f2fs-tools @ 2015-07-02) runs through fine but does not prevent the error: "fsck.f2fs -af /dev/sdg Info: Fix the reported corruption. Info: Force to fix corruption Info: sector size = 512 Info: total sectors = 62533296 (30533 MB) Info: MKFS version "" Info: FSCK version from "Linux version 4.2.0-1-cu (meme@mememe) (gcc version 5.2.0 (GCC) ) #1 SMP PREEMPT Tue Jul 21 00:13:15 CEST 2015" to "Linux version 4.2.0-1-cu (meme@mememe) (gcc version 5.2.0 (GCC) ) #1 SMP PREEMPT Tue Jul 21 16:35:16 CEST 2015" Info: superblock features = 0 : Info: superblock encrypt level = 0, salt = 00000000000000000000000000000000 Info: total FS sectors = 62533296 (30533 MB) Info: CKPT version = 8057 Info: checkpoint state = 5 : compacted_summary unmount [FSCK] Unreachable nat entries [Ok..] [0x0] [FSCK] SIT valid block bitmap checking [Ok..] [FSCK] Hard link checking for regular file [Ok..] [0x0] [FSCK] valid_block_count matching with CP [Ok..] [0x3fbb3c] [FSCK] valid_node_count matcing with CP (de lookup) [Ok..] [0xa4e54] [FSCK] valid_node_count matcing with CP (nat lookup) [Ok..] [0xa4e54] [FSCK] valid_inode_count matched with CP [Ok..] [0xa4855] [FSCK] free segment_count matched with CP [Ok..] [0x2e6] [FSCK] next block offset is free [Ok..] [FSCK] fixing SIT types [FSCK] other corrupted bugs [Ok..] Done." Kernel is at Linux 4.2-rc3 patched with the commits from dev-test. BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 IP: [<ffffffff8149d82a>] __percpu_counter_add+0x1a/0x90 PGD 127014067 PUD 226f26067 PMD 0 Oops: 0000 [#1] PREEMPT SMP task: ffff8803a422cf80 ti: ffff880139bf8000 task.ti: ffff880139bf8000 RIP: 0010:[<ffffffff8149d82a>] [<ffffffff8149d82a>] __percpu_counter_add+0x1a/0x90 RSP: 0018:ffff880139bfb8b8 EFLAGS: 00010082 RAX: 0000000000000003 RBX: ffffea00062bc9c0 RCX: 0000000000000001 RDX: 0000000000000020 RSI: 0000000000000001 RDI: 0000000000000088 RBP: ffff880139bfb8d8 R08: 0000000000000000 R09: ffff88014156afc8 R10: 00000000fffffffa R11: 0000000000000000 R12: 0000000000000088 R13: 0000000000000001 R14: ffff88041d099000 R15: ffff880099ce5740 FS: 00007f0e69cc5840(0000) GS:ffff88042f280000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000a8 CR3: 0000000114c31000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: 0000000000000000 ffffea00062bc9c0 ffff880099ce58a8 ffff880099ce58c0 ffff880139bfb938 ffffffff811cc97e 00000000002c4df6 0000000000000292 0000000000000000 ffff8800b4850198 0000000000000000 ffffea00062bc9c0 Call Trace: [<ffffffff811cc97e>] __test_set_page_writeback+0xde/0x1d0 [<ffffffff813ffcf7>] do_write_data_page+0xe7/0x3a0 [<ffffffff813fae0a>] gc_data_segment+0x5aa/0x640 [<ffffffff813fafd8>] do_garbage_collect+0x138/0x150 [<ffffffff813fb31e>] f2fs_gc+0x1be/0x3e0 [<ffffffff81406451>] f2fs_balance_fs+0x81/0x90 [<ffffffff813fdf93>] f2fs_write_begin+0x73/0x5e0 [<ffffffff81426963>] ? security_file_open+0x93/0xa0 [<ffffffff811c2fee>] generic_perform_write+0xbe/0x1d0 [<ffffffff812485a9>] ? generic_update_time+0x79/0xc0 [<ffffffff811c4560>] __generic_file_write_iter+0x190/0x1f0 [<ffffffff811c469d>] generic_file_write_iter+0xdd/0x1f0 [<ffffffff813ea83e>] f2fs_file_write_iter+0xe/0x10 [<ffffffff8122e61c>] __vfs_write+0xcc/0x100 [<ffffffff8122ee94>] vfs_write+0xa4/0x190 [<ffffffff8122fb85>] SyS_write+0x55/0xc0 [<ffffffff819416ee>] entry_SYSCALL_64_fastpath+0x12/0x71 Code: 41 5e 5d c3 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 55 49 89 f5 41 54 49 89 fc 53 48 83 ec 08 65 ff 05 a6 e0 b6 7e <48> 8b 47 20 48 63 ca 65 8b 18 48 63 db 48 01 f3 48 39 cb 7d 0a RIP [<ffffffff8149d82a>] __percpu_counter_add+0x1a/0x90
Thank you for the report. It seems that this is caused by recent changes on other components. I'll do bisect.
Another one, perhaps of use as it's a bit shorter: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 IP: [<ffffffff8149deea>] __percpu_counter_add+0x1a/0x90 PGD 2951ff067 PUD 2df43f067 PMD 0 Oops: 0000 [#1] PREEMPT SMP Modules linked in: CPU: 7 PID: 10356 Comm: gcc Tainted: G W 4.2.0-1-cu #1 Hardware name: Gigabyte Technology Co., Ltd. G1.Sniper M5/G1.Sniper M5, BIOS T01 02/03/2015 task: ffff880295044f80 ti: ffff880295140000 task.ti: ffff880295140000 RIP: 0010:[<ffffffff8149deea>] [<ffffffff8149deea>] __percpu_counter_add+0x1a/0x90 RSP: 0018:ffff880295143ac8 EFLAGS: 00010082 RAX: 0000000000000003 RBX: ffffea000a526d40 RCX: 0000000000000001 RDX: 0000000000000020 RSI: 0000000000000001 RDI: 0000000000000088 RBP: ffff880295143ae8 R08: 0000000000000000 R09: ffff88008f69bb30 R10: 00000000fffffffa R11: 0000000000000000 R12: 0000000000000088 R13: 0000000000000001 R14: ffff88041d099000 R15: ffff880084a205d0 FS: 00007f8549374700(0000) GS:ffff88042f3c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000a8 CR3: 000000033e1d5000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: 0000000000000000 ffffea000a526d40 ffff880084a20738 ffff880084a20750 ffff880295143b48 ffffffff811cc91e ffff880000000000 0000000000000296 0000000000000000 ffff880417090198 0000000000000000 ffffea000a526d40 Call Trace: [<ffffffff811cc91e>] __test_set_page_writeback+0xde/0x1d0 [<ffffffff813fee87>] do_write_data_page+0xe7/0x3a0 [<ffffffff813faeea>] gc_data_segment+0x5aa/0x640 [<ffffffff813fb0b8>] do_garbage_collect+0x138/0x150 [<ffffffff813fb3fe>] f2fs_gc+0x1be/0x3e0 [<ffffffff81405541>] f2fs_balance_fs+0x81/0x90 [<ffffffff813ee357>] f2fs_unlink+0x47/0x1d0 [<ffffffff81239329>] vfs_unlink+0x109/0x1b0 [<ffffffff8123e3d7>] do_unlinkat+0x287/0x2c0 [<ffffffff8123ebc6>] SyS_unlink+0x16/0x20 [<ffffffff81942e2e>] entry_SYSCALL_64_fastpath+0x12/0x71 Code: 41 5e 5d c3 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 55 49 89 f5 41 54 49 89 fc 53 48 83 ec 08 65 ff 05 e6 d9 b6 7e <48> 8b 47 20 48 63 ca 65 8b 18 48 63 db 48 01 f3 48 39 cb 7d 0a RIP [<ffffffff8149deea>] __percpu_counter_add+0x1a/0x90 RSP <ffff880295143ac8> CR2: 00000000000000a8 ---[ end trace 5132449a58ed93a3 ]--- note: gcc[10356] exited with preempt_count 2 ------------ System ran for another 60 sec, then dmesg ends with INFO: rcu_preempt detected stalls on CPUs/tasks: { P10356} (detected by 6, t=18002 jiffies, g=49234, c=49233, q=32914) gcc x ffff8802951437d8 0 10356 0 0x00000002 ffff8802951437d8 ffff8800b5359a80 ffff880295044f80 ffff88041c570618 ffff880295144000 ffff880295143830 ffff880295143378 ffff8800830e49e8 0000000000000046 ffff8802951437f8 ffffffff8193f3ce ffff880295143830 Call Trace: [<ffffffff8193f3ce>] schedule+0x3e/0x90 [<ffffffff810e7f1b>] do_exit+0x81b/0xb10 [<ffffffff81066f3e>] oops_end+0x9e/0xd0 [<ffffffff810ac1b3>] no_context+0x163/0x370 [<ffffffff8147aefd>] ? radix_tree_lookup+0xd/0x10 [<ffffffff810ac4e5>] __bad_area_nosemaphore+0x125/0x230 [<ffffffff814005db>] ? get_node_info+0x8b/0x230 [<ffffffff810ac603>] bad_area_nosemaphore+0x13/0x20 [<ffffffff810aca82>] __do_page_fault+0x222/0x450 [<ffffffff814007e0>] ? read_node_page+0x60/0xb0 [<ffffffff810accd2>] do_page_fault+0x22/0x30 [<ffffffff81944c08>] page_fault+0x28/0x30 [<ffffffff8149deea>] ? __percpu_counter_add+0x1a/0x90 [<ffffffff8122117a>] ? mem_cgroup_begin_page_stat+0x1a/0xa0 [<ffffffff811cc91e>] __test_set_page_writeback+0xde/0x1d0 [<ffffffff813fee87>] do_write_data_page+0xe7/0x3a0 [<ffffffff813faeea>] gc_data_segment+0x5aa/0x640 [<ffffffff813fb0b8>] do_garbage_collect+0x138/0x150 [<ffffffff813fb3fe>] f2fs_gc+0x1be/0x3e0 [<ffffffff81405541>] f2fs_balance_fs+0x81/0x90 [<ffffffff813ee357>] f2fs_unlink+0x47/0x1d0 [<ffffffff81239329>] vfs_unlink+0x109/0x1b0 [<ffffffff8123e3d7>] do_unlinkat+0x287/0x2c0 [<ffffffff8123ebc6>] SyS_unlink+0x16/0x20 [<ffffffff81942e2e>] entry_SYSCALL_64_fastpath+0x12/0x71
Everything ok for the past month, so I'll close.