NFS: Fix missing pg_cleanup after nfs_pageio_cond_complete()

Commit a7d42ddb3099727f58366fa006f850a219cce6c8 ("nfs: add mirroring
support to pgio layer") moved pg_cleanup out of the path when there was
non-sequental I/O that needed to be flushed.  The result is that for
layouts that have more than one layout segment per file, the pg_lseg is not
cleared, so we can end up hitting the WARN_ON_ONCE(req_start >= seg_end) in
pnfs_generic_pg_test since the pg_lseg will be pointing to that
previously-flushed layout segment.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Fixes: a7d42ddb3099 ("nfs: add mirroring support to pgio layer")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/pagelist.c

@@ -1256,8 +1256,10 @@ void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
 		mirror = &desc->pg_mirrors[midx];
 		if (!list_empty(&mirror->pg_list)) {
 			prev = nfs_list_entry(mirror->pg_list.prev);
-			if (index != prev->wb_index + 1)
-				nfs_pageio_complete_mirror(desc, midx);
+			if (index != prev->wb_index + 1) {
+				nfs_pageio_complete(desc);
+				break;
+			}
 		}
 	}
 }