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

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Date:	Thu, 18 Oct 2012 19:46:28 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Bryan Schumaker <bjschuma@...app.com>,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [ 04/76] NFS: Remove bad delegations during open recovery

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

------------------

From: Bryan Schumaker <bjschuma@...app.com>

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@...app.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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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