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XArray: Fix xas_pause at ULONG_MAX 

If we were unlucky enough to call xas_pause() when the index was at
ULONG_MAX (or a multi-slot entry which ends at ULONG_MAX), we would
wrap the index back around to 0 and restart the iteration from the
beginning.  Use the XAS_BOUNDS state to indicate that we should just
stop the iteration.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2019-11-07 22:49:11 -05:00
parent 0058b0a506
commit 82a22311b7
2 changed files with 27 additions and 3 deletions
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22
lib/test_xarray.c
View File

@ -1132,6 +1132,27 @@ static noinline void check_move_tiny(struct xarray *xa)
XA_BUG_ON(xa, !xa_empty(xa));
}
static noinline void check_move_max(struct xarray *xa)
{
XA_STATE(xas, xa, 0);
xa_store_index(xa, ULONG_MAX, GFP_KERNEL);
rcu_read_lock();
XA_BUG_ON(xa, xas_find(&xas, ULONG_MAX) != xa_mk_index(ULONG_MAX));
XA_BUG_ON(xa, xas_find(&xas, ULONG_MAX) != NULL);
rcu_read_unlock();
xas_set(&xas, 0);
rcu_read_lock();
XA_BUG_ON(xa, xas_find(&xas, ULONG_MAX) != xa_mk_index(ULONG_MAX));
xas_pause(&xas);
XA_BUG_ON(xa, xas_find(&xas, ULONG_MAX) != NULL);
rcu_read_unlock();
xa_erase_index(xa, ULONG_MAX);
XA_BUG_ON(xa, !xa_empty(xa));
}
static noinline void check_move_small(struct xarray *xa, unsigned long idx)
{
XA_STATE(xas, xa, 0);
@ -1240,6 +1261,7 @@ static noinline void check_move(struct xarray *xa)
xa_destroy(xa);
check_move_tiny(xa);
check_move_max(xa);
for (i = 0; i < 16; i++)
check_move_small(xa, 1UL << i);

8
lib/xarray.c
View File

@ -967,6 +967,7 @@ void xas_pause(struct xa_state *xas)
if (xas_invalid(xas))
return;
xas->xa_node = XAS_RESTART;
if (node) {
unsigned int offset = xas->xa_offset;
while (++offset < XA_CHUNK_SIZE) {
@ -974,10 +975,11 @@ void xas_pause(struct xa_state *xas)
break;
}
xas->xa_index += (offset - xas->xa_offset) << node->shift;
if (xas->xa_index == 0)
xas->xa_node = XAS_BOUNDS;
} else {
xas->xa_index++;
}
xas->xa_node = XAS_RESTART;
}
EXPORT_SYMBOL_GPL(xas_pause);
@ -1079,13 +1081,13 @@ void *xas_find(struct xa_state *xas, unsigned long max)
{
void *entry;
if (xas_error(xas))
if (xas_error(xas) || xas->xa_node == XAS_BOUNDS)
return NULL;
if (!xas->xa_node) {
xas->xa_index = 1;
return set_bounds(xas);
} else if (xas_top(xas->xa_node)) {
} else if (xas->xa_node == XAS_RESTART) {
entry = xas_load(xas);
if (entry || xas_not_node(xas->xa_node))
return entry;