[ 04/76] NFS: Remove bad delegations during open recovery

From: Greg Kroah-Hartman
Date: Thu Oct 18 2012 - 23:05:42 EST

3.6-stable review patch. If anyone has any objections, please let me know.


From: Bryan Schumaker <bjschuma@xxxxxxxxxx>

commit 6938867edba929a65a167a97581231e76aeb10b4 upstream.

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 <bjschuma@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

fs/nfs/nfs4proc.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1774,7 +1774,11 @@ static void nfs41_clear_delegation_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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