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Date:   Fri, 17 Nov 2023 15:38:29 +0100
From:   Heiko Carstens <hca@linux.ibm.com>
To:     Heiko Carstens <hca@linux.ibm.com>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@vger.kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ajay Kaher <akaher@vmware.com>, chinglinyu@google.com,
        lkp@intel.com, namit@vmware.com, oe-lkp@lists.linux.dev,
        amakhalov@vmware.com, er.ajay.kaher@gmail.com,
        srivatsa@csail.mit.edu, tkundu@vmware.com, vsirnapalli@vmware.com,
        linux-s390@vger.kernel.org
Subject: Re: [PATCH v5] eventfs: Remove eventfs_file and just use
 eventfs_inode
Message-ID: <20231117143829.9674-B-hca@linux.ibm.com>
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 <20231117142335.9674-A-hca@linux.ibm.com>
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On Fri, Nov 17, 2023 at 03:23:35PM +0100, Heiko Carstens wrote:
> I think this patch causes from time to time crashes when running ftrace
> selftests. In particular I guess there is a bug wrt error handling in this
> function (see below for call trace):
> 
> > +static struct dentry *
> > +create_file_dentry(struct eventfs_inode *ei, struct dentry **e_dentry,
> > +		   struct dentry *parent, const char *name, umode_t mode, void *data,
> > +		   const struct file_operations *fops, bool lookup)
> > +{
...
> Note that the compare and swap instruction within d_invalidate() generates
> a specification exception because it operates on an invalid address
> (0xffffffffffffffef), which happens to be -EEXIST. So my assumption is that
> create_dir_dentry() has incorrect error handling and passes -EEXIST instead
> of a valid dentry pointer to d_invalidate().
> 
> But I leave it up to you to figure this out :)

Ok, wrong function quoted of course. But the rest of my statement
should be correct.