From: Jan Kara <jack@suse.cz>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Jan Kara <jack@suse.cz>, Tony Lindgren <tony@atomide.com>,
Eric Biggers <ebiggers@google.com>, Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger@dilger.ca>,
Jaegeuk Kim <jaegeuk@kernel.org>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-omap@vger.kernel.org
Subject: Re: Regression in next with ext4 oops
Date: Wed, 5 Oct 2016 07:44:45 +0200 [thread overview]
Message-ID: <20161005054445.GA20752@quack2.suse.cz> (raw)
In-Reply-To: <20161004145639.GY19539@ZenIV.linux.org.uk>
On Tue 04-10-16 15:56:39, Al Viro wrote:
> On Tue, Oct 04, 2016 at 11:00:41AM +0200, Jan Kara wrote:
> > Hi!
> >
> > On Mon 03-10-16 16:30:55, Tony Lindgren wrote:
> > > I'm seeing a repeatable oops with Linux next while running
> > > update-initramfs, see below. I tried reverting commit 59aa5a3aeead
> > > ("fscrypto: make filename crypto functions return 0 on success")
> > > as that's the only commit changing ext4_htree_store_dirent, but
> > > that did not help.
> > >
> > > Anybody else seeing something like this?
> >
> > Never seen this but I suspect it is a fallout from Al's directory locking
> > changes. In particular ext4_htree_fill_tree() builds rb-tree of found
> > directory entries in file->private_data (and generally modifies the
> > structure stored there) but after Al's changes we don't have exclusive
> > access to struct file if I'm right so if two processes end up calling
> > getdents() for the same 'struct file' we are doomed.
>
> RTFS. We sure as hell *do* have exclusive access to struct file. See
> /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
> if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
> f->f_mode |= FMODE_ATOMIC_POS;
> in do_dentry_open() as well as
> if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
> if (file_count(file) > 1) {
> v |= FDPUT_POS_UNLOCK;
> mutex_lock(&file->f_pos_lock);
> }
> }
> in __fdget_pos() and
> f = fdget_pos(fd);
> if (!f.file)
> return -EBADF;
> in getdents(2).
Yeah, sorry. I've misunderstood how the FMODE_ATOMIC_POS thing works...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
prev parent reply other threads:[~2016-10-05 5:44 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-03 23:30 Regression in next with ext4 oops Tony Lindgren
2016-10-04 9:00 ` Jan Kara
2016-10-04 14:02 ` Theodore Ts'o
2016-10-04 14:44 ` Tony Lindgren
2016-10-04 14:59 ` Al Viro
2016-10-04 19:07 ` Theodore Ts'o
2016-10-04 19:19 ` Tony Lindgren
2016-10-04 19:16 ` Tony Lindgren
2016-10-04 19:29 ` Tony Lindgren
2016-10-04 19:41 ` Kalle Valo
2016-10-04 20:34 ` Tony Lindgren
2016-10-05 9:51 ` Kalle Valo
2016-10-04 14:18 ` Tony Lindgren
2016-10-04 14:56 ` Al Viro
2016-10-05 5:44 ` Jan Kara [this message]
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