XArray: Fix xas_next() with a single entry at 0

If there is only a single entry at 0, the first time we call xas_next(),
we return the entry.  Unfortunately, all subsequent times we call
xas_next(), we also return the entry at 0 instead of noticing that the
xa_index is now greater than zero.  This broke find_get_pages_contig().

Fixes: 64d3e9a9e0cc ("xarray: Step through an XArray")
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/xarray.c b/lib/xarray.c
index 446b956c9188..1237c213f52b 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -994,6 +994,8 @@ void *__xas_prev(struct xa_state *xas)
 
 	if (!xas_frozen(xas->xa_node))
 		xas->xa_index--;
+	if (!xas->xa_node)
+		return set_bounds(xas);
 	if (xas_not_node(xas->xa_node))
 		return xas_load(xas);
 
@@ -1031,6 +1033,8 @@ void *__xas_next(struct xa_state *xas)
 
 	if (!xas_frozen(xas->xa_node))
 		xas->xa_index++;
+	if (!xas->xa_node)
+		return set_bounds(xas);
 	if (xas_not_node(xas->xa_node))
 		return xas_load(xas);