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authorMatthew Wilcox (Oracle) <willy@infradead.org>2019-07-01 17:03:29 -0400
committerMatthew Wilcox (Oracle) <willy@infradead.org>2019-07-01 17:11:16 -0400
commit91abab83839aa2eba073e4a63c729832fdb27ea1 (patch)
tree3a083d68dc7d4fdca445313c74852943fafbf7f4
parent6fbc7275c7a9ba97877050335f290341a1fd8dbf (diff)
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>
-rw-r--r--lib/test_xarray.c24
-rw-r--r--lib/xarray.c4
2 files changed, 28 insertions, 0 deletions
diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 9d631a7b6a70..7df4f7f395bf 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -1110,6 +1110,28 @@ static noinline void check_find_entry(struct xarray *xa)
XA_BUG_ON(xa, !xa_empty(xa));
}
+static noinline void check_move_tiny(struct xarray *xa)
+{
+ XA_STATE(xas, xa, 0);
+
+ XA_BUG_ON(xa, !xa_empty(xa));
+ rcu_read_lock();
+ XA_BUG_ON(xa, xas_next(&xas) != NULL);
+ XA_BUG_ON(xa, xas_next(&xas) != NULL);
+ rcu_read_unlock();
+ xa_store_index(xa, 0, GFP_KERNEL);
+ rcu_read_lock();
+ xas_set(&xas, 0);
+ XA_BUG_ON(xa, xas_next(&xas) != xa_mk_index(0));
+ XA_BUG_ON(xa, xas_next(&xas) != NULL);
+ xas_set(&xas, 0);
+ XA_BUG_ON(xa, xas_prev(&xas) != xa_mk_index(0));
+ XA_BUG_ON(xa, xas_prev(&xas) != NULL);
+ rcu_read_unlock();
+ xa_erase_index(xa, 0);
+ XA_BUG_ON(xa, !xa_empty(xa));
+}
+
static noinline void check_move_small(struct xarray *xa, unsigned long idx)
{
XA_STATE(xas, xa, 0);
@@ -1217,6 +1239,8 @@ static noinline void check_move(struct xarray *xa)
xa_destroy(xa);
+ check_move_tiny(xa);
+
for (i = 0; i < 16; i++)
check_move_small(xa, 1UL << i);
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);