Patch "NFSv4: Fix a hang in OPEN related to server reboot" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

NFSv4: Fix a hang in OPEN related to server reboot

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nfsv4-fix-a-hang-in-open-related-to-server-reboot.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Trond Myklebust <[email protected]>
Date: Sat, 15 Apr 2017 19:20:01 -0400
Subject: NFSv4: Fix a hang in OPEN related to server reboot

From: Trond Myklebust <[email protected]>

commit 56e0d71ef12f026d96213e45a662bde6bbff4676 upstream.

If the server fails to return the attributes as part of an OPEN reply, and then reboots, we can end up hanging. The reason is that the client attempts to send a GETATTR in order to pick up the missing OPEN call, but fails to release the slot first, causing reboot recovery to deadlock.

---
 fs/nfs/nfs4proc.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -2300,8 +2300,10 @@ static int _nfs4_proc_open(struct nfs4_o
 		if (status != 0)
 			return status;
 	}
-	if (!(o_res->f_attr->valid & NFS_ATTR_FATTR))
+	if (!(o_res->f_attr->valid & NFS_ATTR_FATTR)) {
+		nfs4_sequence_free_slot(&o_res->seq_res);
 		nfs4_proc_getattr(server, &o_res->fh, o_res->f_attr, o_res->f_label);
+	}
 	return 0;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/nfs-use-gfp_noio-for-two-allocations-in-writeback.patch queue-4.11/nfsv4-fix-an-rcu-lock-leak.patch queue-4.11/nfsv4-fix-a-hang-in-open-related-to-server-reboot.patch queue-4.11/nfsd-fix-up-the-supattr_exclcreat-attributes.patch queue-4.11/pnfs-flexfiles-check-the-result-of-nfs4_pnfs_ds_connect.patch queue-4.11/nfs-fix-use-after-free-in-write-error-path.patch