On Wed, Mar 30, 2011 at 6:37 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > On Wed, 30 Mar 2011 14:55:00 -0700 > Mark Moseley <moseleymark@xxxxxxxxx> wrote: > >> > I'm not 100% sure it's related (but I'm going to guess it is) but on >> > these same boxes, they're not actually able to reboot at the end of a >> > graceful shutdown. After yielding that bug and continuing with the >> > shutdown process, it gets all the way to exec'ing: >> > >> > reboot -d -f -i >> > >> > and then just hangs forever. I'm guessing a thread is hung still >> > trying to unmount things. On another box, I triggered that bug with a >> > umount of one top-level mount that had subtrees. When I umount'd >> > another top-level mount with subtrees on that same box, it's blocked >> > and unkillable. That second umount also logged another bug to the >> > kernel logs. >> > >> > In both umounts described above, the entries in /proc/mounts go away >> > after the umount. >> > >> > Jeff, are you at liberty to do a graceful shutdown of the box you saw >> > that bug on? If so, does it actually reboot? >> >> >> A bit more info: On the same boxes, freshly booted but with all the >> same mounts (even the subtrees) mounted, I don't get that bug, so it >> seems to happen just when there's been significant usage within those >> mounts. These are all read-only mounts, if it makes a difference. >> >> I was however able to trigger the bug on a box that had been running >> (web serving) for about 15 minutes. Here's a snippet from slabinfo >> right before umount'ing (let me know if more of it would help): >> > > No, it hung. Unfortunately, I didn't collect any info that told me > where it was hung though. > > I believe that's fairly typical though in situations like this. The > problem is that we likely have a dentry refcount leak somewhere. The > vfsmount refcount was low enough to allow an unmount though. Often > these sorts of problems lurk in error handling code... > >> # grep nfs /proc/slabinfo >> nfsd4_delegations 0 0 360 22 2 : tunables 0 0 >> 0 : slabdata 0 0 0 >> nfsd4_stateids 0 0 120 34 1 : tunables 0 0 >> 0 : slabdata 0 0 0 >> nfsd4_files 0 0 136 30 1 : tunables 0 0 >> 0 : slabdata 0 0 0 >> nfsd4_stateowners 0 0 424 38 4 : tunables 0 0 >> 0 : slabdata 0 0 0 >> nfs_direct_cache 0 0 136 30 1 : tunables 0 0 >> 0 : slabdata 0 0 0 >> nfs_write_data 46 46 704 23 4 : tunables 0 0 >> 0 : slabdata 2 2 0 >> nfs_read_data 207 207 704 23 4 : tunables 0 0 >> 0 : slabdata 9 9 0 >> nfs_inode_cache 23901 23901 1056 31 8 : tunables 0 0 >> 0 : slabdata 771 771 0 >> nfs_page 256 256 128 32 1 : tunables 0 0 >> 0 : slabdata 8 8 0 > > slabinfo probably won't tell us much here. If we can narrow down the > reproducer for this though then that would definitely help. > Actually, /proc/self/mountstats might give us something to go on... Would turning on kmemleak and letting it run for a bit (luckily 15 mins of regular use seems to be enough to trigger this bug) tell us anything? I can do that easily enough but I don't know if it tracks dentry entries. Also I'll grab mountstats as well before/after trying a umount. Anything in particular within mountstats I should pay close attention to? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
