On Wed, Aug 16, 2023 at 7:11 PM Guenter Roeck <li...@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 <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.
> >
>
> 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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