Hi,
I've encountered a bug that triggers a warning message ("list_del
corruption. next->prev should be d9d0ae28, but was d9d5d5e8") and
subsequently causes a null pointer dereference while running a custom
test case on btrfs (kernel 3.11.1), inside a QEMU based VM.
The bug was triggered during the execution of two concurrent sync() calls.
Here's the list of FS operations executed immediately before the crash:
CPU: 0 Op: fdatasync
CPU: 0 Op: btrfs_ioctl_device_delete
CPU: 0 Op: rename (file: "d16/da6/l131" renamed to "d16/d21/d38/l13b")
CPU: 0 Op: btrfs_subvol_snapshot
CPU: 1 Op: fdatasync
CPU: 1 Op: btrfs_ioctl_device_delete
CPU: 1 Op: rename (file: "d16/da6/l131" renamed to
"d16/d21/d38/l13b")
CPU: 1 Op: btrfs_subvol_snapshot
CPU: 0 Op: dwrite (file: "d16/d21/f51")
CPU: 0 Op: chown (file: "d16/da6/f114")
CPU: 0 Op: write (file: "d16/d21/f107")
CPU: 0 Op: sync
CPU: 1 Op: dwrite (file: "d16/d21/f51")
CPU: 1 Op: chown (file: "d16/c1c")
CPU: 1 Op: write (file: "d16/d21/f107")
CPU: 1 Op: sync
(Note that the entries in this log refer to the moment when the
operations were initiated, i.e., operations on different CPUs may overlap):
And here's the system log output:
[ 127.830656] ------------[ cut here ]------------
[ 127.830656] WARNING: CPU: 0 PID: 2791 at
/local/pfonseca/piking/kernel-build/linux-3.11.1-fs-static/lib/list_debug.c:62
__list_del_entry+0x62/0x71()
[ 127.830656] list_del corruption. next->prev should be d9d0ae28, but
was d9d5d5e8
[ 127.830656] Modules linked in: loop rtc_cmos pcspkr tpm_tis
freq_table mperf i2c_piix4
[ 127.830656] CPU: 0 PID: 2791 Comm: fsstress Not tainted 3.11.1 #2
[ 127.830656] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
[ 127.830656] 0000003e c4027dd8 c176917a c1a13c6e c4027df0 c102d1c0
c138838f d9d0ae28
[ 127.830656] d9d0ae28 d9d0ade0 c4027e08 c102d23b 00000009 c4027e00
c1a13dad c4027e1c
[ 127.830656] c4027e28 c138838f c1a13c6e 0000003e c1a13dad d9d0ae28
d9d5d5e8 d9d0ade0
[ 127.830656] Call Trace:
[ 127.830656] [<c176917a>] dump_stack+0x41/0x57
[ 127.830656] [<c102d1c0>] warn_slowpath_common+0x5e/0x75
[ 127.830656] [<c138838f>] ? __list_del_entry+0x62/0x71
[ 127.830656] [<c102d23b>] warn_slowpath_fmt+0x26/0x2a
[ 127.830656] [<c138838f>] __list_del_entry+0x62/0x71
[ 127.830656] [<c12a8564>] run_clustered_refs+0x877/0x8b0
[ 127.830656] [<c12eed36>] ? btrfs_find_ref_cluster+0xc9/0x10e
[ 127.830656] [<c12a878f>] btrfs_run_delayed_refs+0x1f2/0x35b
[ 127.830656] [<c1075d14>] ? __delayacct_blkio_end+0x30/0x36
[ 127.830656] [<c12b56b9>] btrfs_commit_transaction+0x60/0x986
[ 127.830656] [<c12b6657>] ? start_transaction+0x320/0x3cd
[ 127.830656] [<c12b671b>] ? btrfs_attach_transaction_barrier+0x17/0x3c
[ 127.830656] [<c1295b1a>] btrfs_sync_fs+0x4c/0x53
[ 127.830656] [<c10c6f1b>] sync_fs_one_sb+0x17/0x19
[ 127.830656] [<c10acab0>] iterate_supers+0x54/0x95
[ 127.830656] [<c10c6f04>] ? SyS_splice+0x455/0x455
[ 127.830656] [<c10c72dd>] sys_sync+0x46/0x70
[ 127.830656] [<c176c2fe>] sysenter_do_call+0x12/0x26
[ 127.830656] ---[ end trace 626899e11111abbe ]---
[ 127.830656] BUG: unable to handle kernel NULL pointer dereference
at (null)
[ 127.830656] IP: [<c137ed3d>] rb_erase+0x177/0x236
[ 127.830656] *pde = 00000000
[ 127.830656] Oops: 0000 [#1] SMP
[ 127.830656] Modules linked in: loop rtc_cmos pcspkr tpm_tis
freq_table mperf i2c_piix4
[ 127.830656] CPU: 0 PID: 2791 Comm: fsstress Tainted: G W 3.11.1 #2
[ 127.830656] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
[ 127.830656] task: de60efc0 ti: c4026000 task.ti: c4026000
[ 127.830656] EIP: 0060:[<c137ed3d>] EFLAGS: 00000246 CPU: 0
[ 127.830656] EIP is at rb_erase+0x177/0x236
[ 127.830656] EAX: 00000000 EBX: 00000000 ECX: d9d0d180 EDX: d9cebddc
[ 127.830656] ESI: 00000001 EDI: d9d0ade0 EBP: c4027e28 ESP: c4027e18
[ 127.830656] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[ 127.830656] CR0: 8005003b CR2: 00000000 CR3: 059d8000 CR4: 00000690
[ 127.830656] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[ 127.830656] DR6: 00000000 DR7: 00000000
[ 127.830656] Stack:
[ 127.830656] d9d0ade0 d9d0ade0 00000000 d9d0ade0 c4027eb8 c12a7fe0
00000000 00000001
[ 127.830656] 00000000 00000002 00000000 c4027f0c 00cc9a28 d9cebddc
de4d1000 0000095c
[ 127.830656] de4d1000 00000007 00000000 0000001e d9cebd60 00000000
00000000 d9cebde0
[ 127.830656] Call Trace:
[ 127.830656] [<c12a7fe0>] run_clustered_refs+0x2f3/0x8b0
[ 127.830656] [<c12eed36>] ? btrfs_find_ref_cluster+0xc9/0x10e
[ 127.830656] [<c12a878f>] btrfs_run_delayed_refs+0x1f2/0x35b
[ 127.830656] [<c1075d14>] ? __delayacct_blkio_end+0x30/0x36
[ 127.830656] [<c12b56b9>] btrfs_commit_transaction+0x60/0x986
[ 127.830656] [<c12b6657>] ? start_transaction+0x320/0x3cd
[ 127.830656] [<c12b671b>] ? btrfs_attach_transaction_barrier+0x17/0x3c
[ 127.830656] [<c1295b1a>] btrfs_sync_fs+0x4c/0x53
[ 127.830656] [<c10c6f1b>] sync_fs_one_sb+0x17/0x19
[ 127.830656] [<c10acab0>] iterate_supers+0x54/0x95
[ 127.830656] [<c10c6f04>] ? SyS_splice+0x455/0x455
[ 127.830656] [<c10c72dd>] sys_sync+0x46/0x70
[ 127.830656] [<c176c2fe>] sysenter_do_call+0x12/0x26
[ 127.830656] Code: 73 04 85 f6 89 70 08 89 43 04 89 59 04 74 07 89
c7 83 cf 01 89 3e 89 c6 89 d8 8b 58 08 89 59 04 89 48 08 e9 8c 00 00
00 8b 41 08 <f6> 00 01 75 2e 8b 58 04 89 ce 83 ce 01 89 59 08 89 48 04
89 33
[ 127.830656] EIP: [<c137ed3d>] rb_erase+0x177/0x236 SS:ESP 0068:c4027e18
[ 127.830656] CR2: 0000000000000000
[ 127.830656] ---[ end trace 626899e11111abbf ]---
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