Re: [syzbot] [xfs?] INFO: task hung in __fdget_pos (4)

[Christian Brauner]

On Mon, Sep 04, 2023 at 09:09:48AM +1000, Dave Chinner wrote:
> On Mon, Sep 04, 2023 at 12:47:53AM +0200, Mateusz Guzik wrote:
> > On 9/4/23, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> > > On Sun, Sep 03, 2023 at 10:33:57AM +0200, Mateusz Guzik wrote:
> > >> On Sun, Sep 03, 2023 at 03:25:28PM +1000, Dave Chinner wrote:
> > >> > On Sat, Sep 02, 2023 at 09:11:34PM -0700, syzbot wrote:
> > >> > > Hello,
> > >> > >
> > >> > > syzbot found the following issue on:
> > >> > >
> > >> > > HEAD commit:    b97d64c72259 Merge tag
> > >> > > '6.6-rc-smb3-client-fixes-part1' of..
> > >> > > git tree:       upstream
> > >> > > console output:
> > >> > > https://syzkaller.appspot.com/x/log.txt?x=14136d8fa80000
> > >> > > kernel config:
> > >> > > https://syzkaller.appspot.com/x/.config?x=958c1fdc38118172
> > >> > > dashboard link:
> > >> > > https://syzkaller.appspot.com/bug?extid=e245f0516ee625aaa412
> > >> > > compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for
> > >> > > Debian) 2.40
> > >> > >
> > >> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >> >
> > >> > Been happening for months, apparently, yet for some reason it now
> > >> > thinks a locking hang in __fdget_pos() is an XFS issue?
> > >> >
> > >> > #syz set subsystems: fs
> > >> >
> > >>
> > >> The report does not have info necessary to figure this out -- no
> > >> backtrace for whichever thread which holds f_pos_lock. I clicked on a
> > >> bunch of other reports and it is the same story.
> > >
> > > That's true, but there's nothing that points at XFS in *any* of the
> > > bug reports. Indeed, log from the most recent report doesn't have
> > > any of the output from the time stuff hung. i.e. the log starts
> > > at kernel time 669.487771 seconds, and the hung task report is at:
> > >
> > 
> > I did not mean to imply this is an xfs problem.
> > 
> > You wrote reports have been coming in for months so it is pretty clear
> > nobody is investigating.
> 
> Which is pretty much the case for all filesystem bug reports from
> syzbot except for those reported against XFS. Almost nobody else is

I'll try to address syzkaller reports that we do get for VFS issues
asap but often they're just not VFS issues or have no reproducer.