On Nov 25, 2013, at 14:27, Adamson, Andy <William.Adamson@xxxxxxxxxx> wrote: > > On Nov 25, 2013, at 1:33 PM, "Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> > wrote: > >> >> On Nov 25, 2013, at 13:13, Myklebust, Trond <Trond.Myklebust@xxxxxxxxxx> wrote: >> >>> >>> On Nov 25, 2013, at 12:57, <andros@xxxxxxxxxx> <andros@xxxxxxxxxx> wrote: >>> >>>> From: Andy Adamson <andros@xxxxxxxxxx> >>>> >>>> The state manager is recovering expired state and recovery OPENs are being >>>> processed. If kswapd is pruning inodes at the same time, a deadlock can occur >>>> when kswapd calls evict_inode on an NFSv4.1 inode with a layout, and the >>>> resultant layoutreturn gets an error that the state mangager is to handle, >>>> causing the layoutreturn to wait on the (NFS client) cl_rpcwaitq. >>>> >>>> At the same time an open is waiting for the inode deletion to complete in >>>> __wait_on_freeing_inode. >>>> >>>> If the open is either the open called by the state manager, or an open from >>>> the same open owner that is holding the NFSv4.0 sequence id which causes the >>>> OPEN from the state manager to wait for the sequence id on the Seqid_waitqueue, >>>> then the state is deadlocked with kswapd. >>>> >>>> Do not handle LAYOUTRETURN errors when called from nfs4_evict_inode. >>> >>> Why are we waiting for recovery in LAYOUTRETURN at all? Layouts are automatically lost when the server reboots or when the lease is otherwise lost. >>> >>> IOW: Is there any reason why we need to special-case nfs4_evict_inode? Shouldn’t we just bail out on error in _all_ cases? >> >> BTW: Is it possible that we might have a similar problem with delegreturn? That too can be called from nfs4_evict_inode… > > Yes, good point. kswapd could be waiting for a delegation to return which has an error along with the same scenario with sys_open and the state manager running. > > With delegreturn, we most definately want to limit 'no error handling' to the evict inode case. Ah… I forgot that the delegreturn in nfs4_evict_inode is asynchronous and doesn’t wait for completion, so it shouldn’t be a problem here. Cheers Trond-- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
