linux-kernel - Re: [PATCH v5] eventfs: Remove eventfs_file and just use eventfs

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Message-ID: <20231117143829.9674-B-hca@linux.ibm.com>
Date:   Fri, 17 Nov 2023 15:38:29 +0100
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ajay Kaher <akaher@...are.com>, chinglinyu@...gle.com,
        lkp@...el.com, namit@...are.com, oe-lkp@...ts.linux.dev,
        amakhalov@...are.com, er.ajay.kaher@...il.com,
        srivatsa@...il.mit.edu, tkundu@...are.com, vsirnapalli@...are.com,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v5] eventfs: Remove eventfs_file and just use
 eventfs_inode

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.