linux-kernel - Re: [syzbot] possible deadlock in ovl_maybe_copy

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Message-ID: <c8306569f880021bae853caf9f347e7c806ffaaa.camel@linux.ibm.com>
Date:   Tue, 22 Jun 2021 07:40:53 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Hillf Danton <hdanton@...a.com>,
        syzbot <syzbot+c18f2f6a7b08c51e3025@...kaller.appspotmail.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot] possible deadlock in ovl_maybe_copy_up

> > Should annotating the iint be limited to files on overlay filesystems?
> >
> 
> Not to overlay files specifically but to files on stacked fs,
> i.e. (inode->i_sb->s_stack_depth > 0)
> Assuming that this patch is tested(?), how come it did not hit the
> WARN_ON_ONCE(depth < 0... above?

Thanks, Amir!

As per the overlayfs comment, the depth can never be 0.  It sounds like
in this case we only want to annotate the iint mutex for regular files,
if the stacking depth is greater than 0, but less than the max depth.

(I'm still trying to reproduce the lockdep.)

Mimi