From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1khrBR-0003tI-Vw for barebox@lists.infradead.org; Wed, 25 Nov 2020 09:33:54 +0000 From: Ahmad Fatoum Message-ID: <6c3e8d1f-025c-73c6-3834-280f0a7e5633@pengutronix.de> Date: Wed, 25 Nov 2020 10:33:45 +0100 MIME-Version: 1.0 Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Infinite Loop when automounting device mounted elsewhere To: Sascha Hauer , "barebox@lists.infradead.org" Hello, I just ran into this issue: $ mkdir /boot $ mount /dev/mmc2.0 /boot $ ls /mnt/mmc2.0/ mounted /dev/mmc2.0 on /boot mounted /dev/mmc2.0 on /boot mounted /dev/mmc2.0 on /boot [ Ad infinitum ] This is more readily reproducible with barebox platforms where a separate boot partition is default-mounted as /boot. In that case, accessing the partition's corresponding /mnt entry will hang. The hang can be traced back to fs/fs.c:follow_managed(): while (managed = path->dentry->d_flags, managed &= DCACHE_MANAGED_DENTRY, managed != 0) { if (managed & DCACHE_MOUNTED) { struct vfsmount *mounted = lookup_mnt(path); if (mounted) { dput(path->dentry); if (need_mntput) mntput(path->mnt); path->mnt = mounted; path->dentry = dget(mounted->mnt_root); need_mntput = true; continue; } } /* Handle an automount point */ if (managed & DCACHE_NEED_AUTOMOUNT) { ret = follow_automount(path, nd, &need_mntput); if (ret < 0) break; continue; } /* We didn't change the current path point */ break; } The code attempts the follow_automount, which would succeed here, but it doesn't actually mount the current mount point, so we never enter the first if clause that would change path->dentry and lead us out of the loop. I am unsure at what layer this should be fixed. Any suggestions? Cheers, Ahmad -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox