[f2fs-dev] circular locking dependency warning in f2fs

[f2fs-dev] circular locking dependency warning in f2fs

[Guenter Roeck]

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);
[   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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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Jaegeuk Kim]

Hi,

On Tue, Aug 15, 2023 at 10:09 PM Guenter Roeck <linux@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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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Guenter Roeck]

On Wed, Aug 16, 2023 at 10:25:06AM -0700, Jaegeuk Kim wrote:
> Hi,
> 
> On Tue, Aug 15, 2023 at 10:09 PM Guenter Roeck <linux@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.
> 

Based on your feedback, am I correct assuming that you don't plan
to fix this ?

Thanks,
Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Jaegeuk Kim]

On Wed, Aug 16, 2023 at 7:11 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Wed, Aug 16, 2023 at 10:25:06AM -0700, Jaegeuk Kim wrote:
> > Hi,
> >
> > On Tue, Aug 15, 2023 at 10:09 PM Guenter Roeck <linux@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.
> >
>
> Based on your feedback, am I correct assuming that you don't plan
> to fix this ?

I'm quite open to something that I may miss. Chao, what do you think?

>
> Thanks,
> Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Guenter Roeck]

On Wed, Aug 16, 2023 at 08:52:19PM -0700, Jaegeuk Kim wrote:
> On Wed, Aug 16, 2023 at 7:11 PM Guenter Roeck <linux@roeck-us.net> wrote:
> >
> > On Wed, Aug 16, 2023 at 10:25:06AM -0700, Jaegeuk Kim wrote:
> > > Hi,
> > >
> > > On Tue, Aug 15, 2023 at 10:09 PM Guenter Roeck <linux@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.
> > >
> >
> > Based on your feedback, am I correct assuming that you don't plan
> > to fix this ?
> 
> I'm quite open to something that I may miss. Chao, what do you think?
> 

Just to give you a background: Recently I started boot testing from f2fs.
Apparently my test bed is the only one testing f2fs, meaning I was the
only one reporting that f2fs crashes in v6.1.y. I then extended my j2fs
test coverage to multiple architectures, only to discover that a recent
commit introduced this lockdep splatch.

My tests always run with lockdep debugging enabled. At the same time,
I can not tolerate persistent warnings because those would hide real
problems. As consequence, I disable any feature generating such warnings
if the reponsible maintainer(s) tell me that they won't fix it. In this
context, it doesn't matter if the warning is a false positive or not.

Ultimately I am quite neutral in this regard; it is up to you if you are
going to address the warning or not. I would just like to know if the
above warning is going to be fixed so I can adjust my test coverage
accordingly.

Side question: Does this possibly need down_read_nested() ?

Thanks,
Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Chao Yu]

On 2023/8/17 11:52, Jaegeuk Kim wrote:
> On Wed, Aug 16, 2023 at 7:11 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On Wed, Aug 16, 2023 at 10:25:06AM -0700, Jaegeuk Kim wrote:
>>> Hi,
>>>
>>> On Tue, Aug 15, 2023 at 10:09 PM Guenter Roeck <linux@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)

The call path is as below:

CPU0					CPU1
- f2fs_create
  - f2fs_do_add_link
   - f2fs_down_read(&F2FS_I(dir)->i_xattr_sem);
   lock(dir#1->i_xattr_sem)
					- f2fs_mkdir
					 - f2fs_do_add_link
					  - f2fs_add_regular_entry
					   - f2fs_down_write(&F2FS_I(inode)->i_sem);
					   lock(new_dir_inode->i_sem)
					   - f2fs_init_inode_metadata
					    - __f2fs_get_acl
					     - f2fs_getxattr
					      - f2fs_down_read(&F2FS_I(inode)->i_xattr_sem);
					      lock(dir#2->i_xattr_sem)

    - f2fs_down_write(&F2FS_I(inode)->i_sem);
    lock(new_reg_inode->i_sem)

1. i_xattr_sems were from different directories, otherwise, create and
mkdir may race on dir->i_rwsem.
2. fi->i_sems were from different type of inodes, one is regular, and
another is directory.

>>>                                                     lock(new_inode#2->i_sem)
>>>                                                     lock(dir->i_xattr_sem)
>>> lock(new_inode#1->i_sem)
>>>
>>> This looks fine to me.
>>>
>>
>> Based on your feedback, am I correct assuming that you don't plan
>> to fix this ?
> 
> I'm quite open to something that I may miss. Chao, what do you think?

Jaegeuk, I agree with you, it looks like a false alarm.

Thanks,

> 
>>
>> Thanks,
>> Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Eric Biggers]

On Thu, Aug 17, 2023 at 10:26:12PM +0800, Chao Yu wrote:
> > > >                                                     lock(new_inode#2->i_sem)
> > > >                                                     lock(dir->i_xattr_sem)
> > > > lock(new_inode#1->i_sem)
> > > > 
> > > > This looks fine to me.
> > > > 
> > > 
> > > Based on your feedback, am I correct assuming that you don't plan
> > > to fix this ?
> > 
> > I'm quite open to something that I may miss. Chao, what do you think?
> 
> Jaegeuk, I agree with you, it looks like a false alarm.
> 

False positive lockdep reports still need to be eliminated, for example by
fixing the lockdep annotations.  Otherwise it's impossible to distinguish them
from true positives.

- Eric


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Guenter Roeck]

On Thu, Aug 17, 2023 at 08:53:19AM -0700, Eric Biggers wrote:
> On Thu, Aug 17, 2023 at 10:26:12PM +0800, Chao Yu wrote:
> > > > >                                                     lock(new_inode#2->i_sem)
> > > > >                                                     lock(dir->i_xattr_sem)
> > > > > lock(new_inode#1->i_sem)
> > > > > 
> > > > > This looks fine to me.
> > > > > 
> > > > 
> > > > Based on your feedback, am I correct assuming that you don't plan
> > > > to fix this ?
> > > 
> > > I'm quite open to something that I may miss. Chao, what do you think?
> > 
> > Jaegeuk, I agree with you, it looks like a false alarm.
> > 
> 
> False positive lockdep reports still need to be eliminated, for example by
> fixing the lockdep annotations.  Otherwise it's impossible to distinguish them
> from true positives.
> 

Exactly, and that is why I don't test features with known lockdep annotation
issues. I'll drop f2fs from my list of features to test for the time being.

Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Jaegeuk Kim]

Chao,

Do you have some bandwidth to address this? Otherwise, I'll do some.

Thanks,

On Fri, Aug 18, 2023 at 6:15 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Thu, Aug 17, 2023 at 08:53:19AM -0700, Eric Biggers wrote:
> > On Thu, Aug 17, 2023 at 10:26:12PM +0800, Chao Yu wrote:
> > > > > >                                                     lock(new_inode#2->i_sem)
> > > > > >                                                     lock(dir->i_xattr_sem)
> > > > > > lock(new_inode#1->i_sem)
> > > > > >
> > > > > > This looks fine to me.
> > > > > >
> > > > >
> > > > > Based on your feedback, am I correct assuming that you don't plan
> > > > > to fix this ?
> > > >
> > > > I'm quite open to something that I may miss. Chao, what do you think?
> > >
> > > Jaegeuk, I agree with you, it looks like a false alarm.
> > >
> >
> > False positive lockdep reports still need to be eliminated, for example by
> > fixing the lockdep annotations.  Otherwise it's impossible to distinguish them
> > from true positives.
> >
>
> Exactly, and that is why I don't test features with known lockdep annotation
> issues. I'll drop f2fs from my list of features to test for the time being.
>
> Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Jaegeuk Kim]

May I know if this works?

https://lore.kernel.org/linux-f2fs-devel/20230819003012.3473675-1-jaegeuk@kernel.org/T/#u

On 08/18, Jaegeuk Kim wrote:
> Chao,
> 
> Do you have some bandwidth to address this? Otherwise, I'll do some.
> 
> Thanks,
> 
> On Fri, Aug 18, 2023 at 6:15 AM Guenter Roeck <linux@roeck-us.net> wrote:
> >
> > On Thu, Aug 17, 2023 at 08:53:19AM -0700, Eric Biggers wrote:
> > > On Thu, Aug 17, 2023 at 10:26:12PM +0800, Chao Yu wrote:
> > > > > > >                                                     lock(new_inode#2->i_sem)
> > > > > > >                                                     lock(dir->i_xattr_sem)
> > > > > > > lock(new_inode#1->i_sem)
> > > > > > >
> > > > > > > This looks fine to me.
> > > > > > >
> > > > > >
> > > > > > Based on your feedback, am I correct assuming that you don't plan
> > > > > > to fix this ?
> > > > >
> > > > > I'm quite open to something that I may miss. Chao, what do you think?
> > > >
> > > > Jaegeuk, I agree with you, it looks like a false alarm.
> > > >
> > >
> > > False positive lockdep reports still need to be eliminated, for example by
> > > fixing the lockdep annotations.  Otherwise it's impossible to distinguish them
> > > from true positives.
> > >
> >
> > Exactly, and that is why I don't test features with known lockdep annotation
> > issues. I'll drop f2fs from my list of features to test for the time being.
> >
> > Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Guenter Roeck]

On Fri, Aug 18, 2023 at 05:35:25PM -0700, Jaegeuk Kim wrote:
> May I know if this works?
> 
> https://lore.kernel.org/linux-f2fs-devel/20230819003012.3473675-1-jaegeuk@kernel.org/T/#u
> 

Yes, that fixes the problem for me. That makes me wonder, though:
Why not just use the _nested functions unconditionally ?

Thanks,
Guenter

> On 08/18, Jaegeuk Kim wrote:
> > Chao,
> > 
> > Do you have some bandwidth to address this? Otherwise, I'll do some.
> > 
> > Thanks,
> > 
> > On Fri, Aug 18, 2023 at 6:15 AM Guenter Roeck <linux@roeck-us.net> wrote:
> > >
> > > On Thu, Aug 17, 2023 at 08:53:19AM -0700, Eric Biggers wrote:
> > > > On Thu, Aug 17, 2023 at 10:26:12PM +0800, Chao Yu wrote:
> > > > > > > >                                                     lock(new_inode#2->i_sem)
> > > > > > > >                                                     lock(dir->i_xattr_sem)
> > > > > > > > lock(new_inode#1->i_sem)
> > > > > > > >
> > > > > > > > This looks fine to me.
> > > > > > > >
> > > > > > >
> > > > > > > Based on your feedback, am I correct assuming that you don't plan
> > > > > > > to fix this ?
> > > > > >
> > > > > > I'm quite open to something that I may miss. Chao, what do you think?
> > > > >
> > > > > Jaegeuk, I agree with you, it looks like a false alarm.
> > > > >
> > > >
> > > > False positive lockdep reports still need to be eliminated, for example by
> > > > fixing the lockdep annotations.  Otherwise it's impossible to distinguish them
> > > > from true positives.
> > > >
> > >
> > > Exactly, and that is why I don't test features with known lockdep annotation
> > > issues. I'll drop f2fs from my list of features to test for the time being.
> > >
> > > Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Chao Yu]

On 2023/8/19 1:28, Jaegeuk Kim wrote:
> Chao,
> 
> Do you have some bandwidth to address this? Otherwise, I'll do some.

Jaegeuk, it seems I'm late... anyway, the fix looks good to me.

Thanks,

> 
> Thanks,
> 
> On Fri, Aug 18, 2023 at 6:15 AM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On Thu, Aug 17, 2023 at 08:53:19AM -0700, Eric Biggers wrote:
>>> On Thu, Aug 17, 2023 at 10:26:12PM +0800, Chao Yu wrote:
>>>>>>>                                                      lock(new_inode#2->i_sem)
>>>>>>>                                                      lock(dir->i_xattr_sem)
>>>>>>> lock(new_inode#1->i_sem)
>>>>>>>
>>>>>>> This looks fine to me.
>>>>>>>
>>>>>>
>>>>>> Based on your feedback, am I correct assuming that you don't plan
>>>>>> to fix this ?
>>>>>
>>>>> I'm quite open to something that I may miss. Chao, what do you think?
>>>>
>>>> Jaegeuk, I agree with you, it looks like a false alarm.
>>>>
>>>
>>> False positive lockdep reports still need to be eliminated, for example by
>>> fixing the lockdep annotations.  Otherwise it's impossible to distinguish them
>>> from true positives.
>>>
>>
>> Exactly, and that is why I don't test features with known lockdep annotation
>> issues. I'll drop f2fs from my list of features to test for the time being.
>>
>> Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Jaegeuk Kim]

On 08/18, Guenter Roeck wrote:
> On Fri, Aug 18, 2023 at 05:35:25PM -0700, Jaegeuk Kim wrote:
> > May I know if this works?
> > 
> > https://lore.kernel.org/linux-f2fs-devel/20230819003012.3473675-1-jaegeuk@kernel.org/T/#u
> > 
> 
> Yes, that fixes the problem for me. That makes me wonder, though:
> Why not just use the _nested functions unconditionally ?

I think we should ignore that in this case only.

> 
> Thanks,
> Guenter
> 
> > On 08/18, Jaegeuk Kim wrote:
> > > Chao,
> > > 
> > > Do you have some bandwidth to address this? Otherwise, I'll do some.
> > > 
> > > Thanks,
> > > 
> > > On Fri, Aug 18, 2023 at 6:15 AM Guenter Roeck <linux@roeck-us.net> wrote:
> > > >
> > > > On Thu, Aug 17, 2023 at 08:53:19AM -0700, Eric Biggers wrote:
> > > > > On Thu, Aug 17, 2023 at 10:26:12PM +0800, Chao Yu wrote:
> > > > > > > > >                                                     lock(new_inode#2->i_sem)
> > > > > > > > >                                                     lock(dir->i_xattr_sem)
> > > > > > > > > lock(new_inode#1->i_sem)
> > > > > > > > >
> > > > > > > > > This looks fine to me.
> > > > > > > > >
> > > > > > > >
> > > > > > > > Based on your feedback, am I correct assuming that you don't plan
> > > > > > > > to fix this ?
> > > > > > >
> > > > > > > I'm quite open to something that I may miss. Chao, what do you think?
> > > > > >
> > > > > > Jaegeuk, I agree with you, it looks like a false alarm.
> > > > > >
> > > > >
> > > > > False positive lockdep reports still need to be eliminated, for example by
> > > > > fixing the lockdep annotations.  Otherwise it's impossible to distinguish them
> > > > > from true positives.
> > > > >
> > > >
> > > > Exactly, and that is why I don't test features with known lockdep annotation
> > > > issues. I'll drop f2fs from my list of features to test for the time being.
> > > >
> > > > Guenter


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Re: [f2fs-dev] circular locking dependency warning in f2fs

[Guenter Roeck]

On Mon, Aug 21, 2023 at 12:37:12PM -0700, Jaegeuk Kim wrote:
> On 08/18, Guenter Roeck wrote:
> > On Fri, Aug 18, 2023 at 05:35:25PM -0700, Jaegeuk Kim wrote:
> > > May I know if this works?
> > > 
> > > https://lore.kernel.org/linux-f2fs-devel/20230819003012.3473675-1-jaegeuk@kernel.org/T/#u
> > > 
> > 
> > Yes, that fixes the problem for me. That makes me wonder, though:
> > Why not just use the _nested functions unconditionally ?
> 
> I think we should ignore that in this case only.
> 

Not sure I understand. If CONFIG_DEBUG_LOCK_ALLOC is not enabled,
the _nested functions map to the standard (unnested) functions.

From include/linux/rwsem.h:

#ifdef CONFIG_DEBUG_LOCK_ALLOC
...
#else
# define down_read_nested(sem, subclass)                down_read(sem)
# define down_read_killable_nested(sem, subclass)       down_read_killable(sem)
# define down_write_nest_lock(sem, nest_lock)   down_write(sem)
# define down_write_nested(sem, subclass)       down_write(sem)
# define down_write_killable_nested(sem, subclass)      down_write_killable(sem)
# define down_read_non_owner(sem)               down_read(sem)
# define up_read_non_owner(sem)                 up_read(sem)
#endif

All you accomplish with the additional set of #ifdefs is to make the
code more difficult to read.

Never mind, I guess this is your call to make.

Guenter


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