Hi,
On Tue, Aug 15, 2023 at 10:09 PM Guenter Roeck <li...@roeck-us.net> wrote:
>
> Hi,
>
> when trying to boot from an f2fs file system with lock debugging enabled,
> I get the attached circular locking dependency warning. Is this a known
> problem ?
>
> Thanks,
> Guenter
>
> ---
> [ 10.315522] ======================================================
> [ 10.315620] WARNING: possible circular locking dependency detected
> [ 10.315753] 6.5.0-rc6-00027-g91aa6c412d7f #1 Tainted: G N
> [ 10.315843] ------------------------------------------------------
> [ 10.315922] seedrng/717 is trying to acquire lock:
> [ 10.316010] ffff8e0e02c6b868 (&fi->i_sem){+.+.}-{3:3}, at:
> f2fs_add_inline_entry+0x134/0x2d0
> [ 10.316315]
> [ 10.316315] but task is already holding lock:
> [ 10.316391] ffff8e0e02c6b278 (&fi->i_xattr_sem){.+.+}-{3:3}, at:
> f2fs_add_dentry+0x41/0xc0
> [ 10.316543]
> [ 10.316543] which lock already depends on the new lock.
> [ 10.316543]
> [ 10.316641]
> [ 10.316641] the existing dependency chain (in reverse order) is:
> [ 10.316745]
> [ 10.316745] -> #1 (&fi->i_xattr_sem){.+.+}-{3:3}:
> [ 10.316883] down_read+0x3d/0x170
> [ 10.316973] f2fs_getxattr+0x370/0x440
> [ 10.317036] __f2fs_get_acl+0x38/0x1e0
> [ 10.317094] f2fs_init_acl+0x69/0x420
> [ 10.317151] f2fs_init_inode_metadata+0x72/0x450
> [ 10.317218] f2fs_add_regular_entry+0x372/0x510
> [ 10.317283] f2fs_add_dentry+0xb8/0xc0
> [ 10.317340] f2fs_do_add_link+0xd9/0x110
> [ 10.317399] f2fs_mkdir+0xdf/0x180
> [ 10.317453] vfs_mkdir+0x142/0x220
> [ 10.317508] do_mkdirat+0x7c/0x120
> [ 10.317561] __x64_sys_mkdir+0x47/0x70
> [ 10.317617] do_syscall_64+0x3f/0x90
> [ 10.317673] entry_SYSCALL_64_after_hwframe+0x73/0xdd
> [ 10.317757]
> [ 10.317757] -> #0 (&fi->i_sem){+.+.}-{3:3}:
> [ 10.317843] __lock_acquire+0x16bf/0x2860
> [ 10.317907] lock_acquire+0xcc/0x2c0
> [ 10.317962] down_write+0x3a/0xc0
> [ 10.318014] f2fs_add_inline_entry+0x134/0x2d0
> [ 10.318077] f2fs_add_dentry+0x55/0xc0
> [ 10.318141] f2fs_do_add_link+0xd9/0x110
> [ 10.318201] f2fs_create+0xe8/0x170
> [ 10.318255] lookup_open.isra.0+0x58e/0x6c0
> [ 10.318317] path_openat+0x2af/0xa40
> [ 10.318372] do_filp_open+0xb1/0x160
> [ 10.318428] do_sys_openat2+0x91/0xc0
> [ 10.318485] __x64_sys_open+0x54/0xa0
> [ 10.318541] do_syscall_64+0x3f/0x90
> [ 10.318597] entry_SYSCALL_64_after_hwframe+0x73/0xdd
> [ 10.318676]
> [ 10.318676] other info that might help us debug this:
> [ 10.318676]
> [ 10.318799] Possible unsafe locking scenario:
> [ 10.318799]
> [ 10.318875] CPU0 CPU1
> [ 10.318935] ---- ----
> [ 10.318999] rlock(&fi->i_xattr_sem);
> [ 10.319068] lock(&fi->i_sem);
> [ 10.319166] lock(&fi->i_xattr_sem);
> [ 10.319264] lock(&fi->i_sem);
It looks like the same one reported by syzbot.
https://syzkaller.appspot.com/bug?extid=a4976ce949df66b1ddf1
However, I suspect it's a false alarm, since I'm interpreting the loop as below.
CPU0 CPU1
lock(new_inode#1->i_xattr_sem)
lock(new_inode#2->i_sem)
lock(dir->i_xattr_sem)
lock(new_inode#1->i_sem)
This looks fine to me.
> [ 10.319325]
> [ 10.319325] *** DEADLOCK ***
> [ 10.319325]
> [ 10.319413] 4 locks held by seedrng/717:
> [ 10.319500] #0: ffff8e0e049693e8 (sb_writers#4){.+.+}-{0:0}, at:
> path_openat+0xa08/0xa40
> [ 10.319645] #1: ffff8e0e02c6ac28 (&type->i_mutex_dir_key#3){++++}-{3:3},
> at: path_openat+0x29b/0xa40
> [ 10.319783] #2: ffff8e0e050623a8 (&sbi->cp_rwsem){.+.+}-{3:3}, at:
> f2fs_create+0xcc/0x170
> [ 10.319899] #3: ffff8e0e02c6b278 (&fi->i_xattr_sem){.+.+}-{3:3}, at:
> f2fs_add_dentry+0x41/0xc0
> [ 10.320029]
> [ 10.320029] stack backtrace:
> [ 10.320166] CPU: 7 PID: 717 Comm: seedrng Tainted: G N
> 6.5.0-rc6-00027-g91aa6c412d7f #1
> [ 10.320302] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
> [ 10.320499] Call Trace:
> [ 10.320579] <TASK>
> [ 10.320665] dump_stack_lvl+0x64/0xb0
> [ 10.320766] check_noncircular+0x151/0x170
> [ 10.320834] ? register_lock_class+0x42/0x7a0
> [ 10.320906] __lock_acquire+0x16bf/0x2860
> [ 10.320974] lock_acquire+0xcc/0x2c0
> [ 10.321026] ? f2fs_add_inline_entry+0x134/0x2d0
> [ 10.321098] down_write+0x3a/0xc0
> [ 10.321156] ? f2fs_add_inline_entry+0x134/0x2d0
> [ 10.321220] f2fs_add_inline_entry+0x134/0x2d0
> [ 10.321290] f2fs_add_dentry+0x55/0xc0
> [ 10.321348] f2fs_do_add_link+0xd9/0x110
> [ 10.321410] f2fs_create+0xe8/0x170
> [ 10.321464] lookup_open.isra.0+0x58e/0x6c0
> [ 10.321536] ? verify_cpu+0x20/0x100
> [ 10.321605] ? verify_cpu+0x20/0x100
> [ 10.321662] path_openat+0x2af/0xa40
> [ 10.321722] do_filp_open+0xb1/0x160
> [ 10.321777] ? alloc_fd+0x3c/0x220
> [ 10.321838] ? _raw_spin_unlock+0x1e/0x40
> [ 10.321901] do_sys_openat2+0x91/0xc0
> [ 10.321959] __x64_sys_open+0x54/0xa0
> [ 10.322014] do_syscall_64+0x3f/0x90
> [ 10.322066] entry_SYSCALL_64_after_hwframe+0x73/0xdd
> [ 10.322182] RIP: 0033:0x7ffbe94532de
> [ 10.322384] Code: c3 8b 07 85 c0 75 24 49 89 fb 48 89 f0 48 89 d7 48 89 ce
> 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> e9
> 4b ce ff ff 41 54 4
> 9 89 f4 be 00 88 08 00 55 53 48 81 ec a0
> [ 10.322619] RSP: 002b:00007ffc0cfc7ed8 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000002
> [ 10.322730] RAX: ffffffffffffffda RBX: 00007ffbe9495b48 RCX:
> 00007ffbe94532de
> [ 10.322821] RDX: 0000000000000100 RSI: 0000000000008241 RDI:
> 000055f2b0816001
> [ 10.322910] RBP: 000055f2b0816001 R08: 0000000000000000 R09:
> 0000000000000000
> [ 10.322999] R10: 0000000000000000 R11: 0000000000000246 R12:
> 0000000000000002
> [ 10.323089] R13: 000055f2b0816001 R14: 000055f2b0816059 R15:
> 00007ffc0cfc8148
> [ 10.323221] </TASK>
> [ 10.383174] seedrng (717) used greatest stack depth: 12624 bytes left
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