NFS: Fix nfs_direct_write_reschedule_io()

The 'hdr->good_bytes' is defined as the number of bytes we expect to
read or write starting at offset hdr->io_start. In the case of a partial
read/write we may end up adjusting hdr->args.offset and hdr->args.count
to skip I/O for data that was already read/written, and so we must ensure
the calculation takes that into account.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/direct.c

@@ -824,7 +824,8 @@ static void nfs_direct_write_reschedule_io(struct nfs_pgio_header *hdr)
 		dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 		/* fake unstable write to let common nfs resend pages */
 		hdr->verf.committed = NFS_UNSTABLE;
-		hdr->good_bytes = hdr->args.count;
+		hdr->good_bytes = hdr->args.offset + hdr->args.count -
+			hdr->io_start;
 	}
 	spin_unlock(&dreq->lock);
 }