Hi Neil, That looks better, but we still want to send the delegation stateid in the case where we have both a lock and a delegation. Cheers Trond Sent from my tablet. NeilBrown <neilb@xxxxxxx> wrote: On Tue, 3 Sep 2013 18:43:23 +0000 "Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> wrote: > On Thu, 2013-08-15 at 12:36 +1000, NeilBrown wrote: > > > > When an NFS (V4 specifically) client loses contact with the server it can > > lose any locks that it holds. > > Currently when it reconnects to the server it simply tries to reclaim > > those locks. This might succeed even though some other client has held and > > released a lock in the mean time. So the first client might think the file > > is unchanged, but it isn't. This isn't good. > > > > If, when recovery happens, the locks cannot be claimed because some other > > client still holds the lock, then we get a message in the kernel logs, but > > the client can still write. So two clients can both think they have a lock > > and can both write at the same time. This is equally not good. > > > > There was a patch a while ago > > http://comments.gmane.org/gmane.linux.nfs/41917 > > > > which tried to address some of this, but it didn't seem to go anywhere. > > That patch would also send a signal to the process. That might be useful > > but I'm really just interested in failing the writes. > > For NFSv4 (unlike v2/v3) there is a strong link between the lock and the > > write request so we can fairly easily fail an IO of the lock is gone. > > > > The patch below attempts to do this. Does it make sense? > > Because this is a fairly big change I introduces a module parameter > > "recover_locks" which defaults to true (the current behaviour) but can be set > > to "false" to tell the client not to try to recover things that were lost. > > > > Comments? > > I think this patch is close to being usable. A couple of questions, > though: > > 1. What happens if another process' open() causes us to receive a > delegation after NFS_LOCK_LOST has been set on our lock stateid, > but before we call nfs4_set_rw_stateid()? Good point. I think we need to check for NFS_LOCK_LOST before checking for a delegation. Does the incremental patch below look OK? It takes a spinlock in the case where we have a delegation and hold some locks which it didn't have to take before. Is that a concern? > 2. Shouldn't we clear NFS_LOCK_LOST at some point? It looks to me > as if a process which sees the EIO, and decides to recover by > calling close(), reopen()ing the file and then locking it again, > might find NFS_LOCK_LOST still being set. NFS_LOCK_LOST is per nfs4_lock_state which should be freed by nfs4_fl_release_lock(). So when the files is closed, the locks a dropped, and the structure holding the NFS_LOCK_LOST flag will go away. Or did I miss something? Thanks, NeilBrown diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 4d103ff..bb1fd5d 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -1040,10 +1040,11 @@ static int nfs4_copy_open_stateid(nfs4_stateid *dst, struct nfs4_state *state) int nfs4_select_rw_stateid(nfs4_stateid *dst, struct nfs4_state *state, fmode_t fmode, const struct nfs_lockowner *lockowner) { - int ret = 0; + int ret = nfs4_copy_lock_stateid(dst, state, lockowner); + if (ret == -EIO) + goto out; if (nfs4_copy_delegation_stateid(dst, state->inode, fmode)) goto out; - ret = nfs4_copy_lock_stateid(dst, state, lockowner); if (ret != -ENOENT) goto out; ret = nfs4_copy_open_stateid(dst, state); -- 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
