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@xxxxxxxx>
SUSE Labs, CR
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