NFS/pnfs: Fix dereference of layout cred in pnfs_layoutcommit_inode()

Ensure that the dereference of the layout cred is atomic with the
stateid.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/pnfs.c

@@ -3137,10 +3137,10 @@ pnfs_layoutcommit_inode(struct inode *inode, bool sync)
 	end_pos = nfsi->layout->plh_lwb;
 
 	nfs4_stateid_copy(&data->args.stateid, &nfsi->layout->plh_stateid);
+	data->cred = get_cred(nfsi->layout->plh_lc_cred);
 	spin_unlock(&inode->i_lock);
 
 	data->args.inode = inode;
-	data->cred = get_cred(nfsi->layout->plh_lc_cred);
 	nfs_fattr_init(&data->fattr);
 	data->args.bitmask = NFS_SERVER(inode)->cache_consistency_bitmask;
 	data->res.fattr = &data->fattr;