The patch below does not apply to the 3.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 6938867edba929a65a167a97581231e76aeb10b4 Mon Sep 17 00:00:00 2001
From: Bryan Schumaker <[email protected]>
Date: Wed, 26 Sep 2012 15:25:52 -0400
Subject: [PATCH] NFS: Remove bad delegations during open recovery

I put the client into an open recovery loop by:
        Client: Open file
                read half
        Server: Expire client (echo 0 > /sys/kernel/debug/nfsd/forget_clients)
        Client: Drop vm cache (echo 3 > /proc/sys/vm/drop_caches)
                finish reading file

This causes a loop because the client never updates the nfs4_state after
discovering that the delegation is invalid.  This means it will keep
trying to read using the bad delegation rather than attempting to re-open
the file.

Signed-off-by: Bryan Schumaker <[email protected]>
CC: [email protected] [3.4+]
Signed-off-by: Trond Myklebust <[email protected]>

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 755ee16..471a75f 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1774,7 +1774,11 @@ static void nfs41_clear_delegation_stateid(struct 
nfs4_state *state)
                 * informs us the stateid is unrecognized. */
                if (status != -NFS4ERR_BAD_STATEID)
                        nfs41_free_stateid(server, stateid);
+               nfs_remove_bad_delegation(state->inode);
 
+               write_seqlock(&state->seqlock);
+               nfs4_stateid_copy(&state->stateid, &state->open_stateid);
+               write_sequnlock(&state->seqlock);
                clear_bit(NFS_DELEGATED_STATE, &state->flags);
        }
 }

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