On Fri, 2014-01-31 at 11:10 +0100, Donald Buczek wrote: > > Hello, Ian, > > you said, "how DCACHE_MOUNTED would not be cleared on umount", so you > are thinking about the unmount path. I asked my users and in two cases > (including the one described in this thread) they think, it happened the > very first time they accessed the path after boot. This suggest, the > problem might appear on the mount path. > > Also, both were on workstations (single user!) and they both used a > shell ( "cd /failing/path" and "do_something > /failing/path/bla" ) , so > collisions (other threads accessing the same path at the same time) are > unlikely. > > We don't have any hints which would suggests, that there might have been > a problem with the fileserver or network involved (which would imply a > bug in the "mount failure" path) Thanks for all this, I appreciate it. snip ... > I've checked the mounts as you asked ( > http://owww.molgen.mpg.de/~buczek/autofs-demo/typescript_3.l ) the > dentry 0xffff88016a31c440 identified in the previous sessions (and still > there) is not in any mnt_mountpoint LOL, it was a long shot and now I know for sure, good. > > How can DCACHE_MOUNTED be set when there was no mount? > The problem appears rarely and (until now) randomly. Locking failure? > > Okay, I've managed to get the nvidia bullshit drivers to work on linux > 3.13.1 , so I'm going to reboot this workstation (with the three > failures) to the latest kernel now with DEBUG set in the autofs4 directory. It's probably a good idea for you to get to some later kernel anyway. See this (not my doing) in 3.8 fs/namei.c /* * Clear dentry's mounted state if it has no remaining mounts. * vfsmount_lock must be held for write. */ static void dentry_reset_mounted(struct dentry *dentry) { unsigned u; for (u = 0; u < HASH_SIZE; u++) { struct mount *p; list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { if (p->mnt_mountpoint == dentry) return; } } spin_lock(&dentry->d_lock); dentry->d_flags &= ~DCACHE_MOUNTED; spin_unlock(&dentry->d_lock); } Which means all dentries in the system need to be scanned before DCACHE_MOUNTED is cleared. Now that's not a problem for a smallish number of mounts but can be a problem for larger numbers of mounts or if there's a large number of dentries in the system. Don't remember exactly when Al Viro fixed it but it's easy to check. > > Perhaps we shouldn't waste to much time analyzing code which is > obsoleted already. I'll surly tell you, when the problem is seen again > with 8.13. Thanks again. Ian -- To unsubscribe from this list: send the line "unsubscribe autofs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
