XArray: Redesign xa_alloc API
It was too easy to forget to initialise the start index. Add an
xa_limit data structure which can be used to pass min & max, and
define a couple of special values for common cases. Also add some
more tests cribbed from the IDR test suite. Change the return value
from -ENOSPC to -EBUSY to match xa_insert().
Signed-off-by: Matthew Wilcox <willy@infradead.org>
diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index cd74f8f..b5a6b98 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -40,9 +40,9 @@ static void *xa_store_index(struct xarray *xa, unsigned long index, gfp_t gfp)
static void xa_alloc_index(struct xarray *xa, unsigned long index, gfp_t gfp)
{
- u32 id = 0;
+ u32 id;
- XA_BUG_ON(xa, xa_alloc(xa, &id, UINT_MAX, xa_mk_index(index),
+ XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(index), xa_limit_32b,
gfp) != 0);
XA_BUG_ON(xa, id != index);
}
@@ -640,28 +640,81 @@ static noinline void check_xa_alloc_1(struct xarray *xa, unsigned int base)
xa_destroy(xa);
/* Check that we fail properly at the limit of allocation */
- id = 0xfffffffeU;
- XA_BUG_ON(xa, xa_alloc(xa, &id, UINT_MAX, xa_mk_index(id),
+ XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(UINT_MAX - 1),
+ XA_LIMIT(UINT_MAX - 1, UINT_MAX),
GFP_KERNEL) != 0);
XA_BUG_ON(xa, id != 0xfffffffeU);
- XA_BUG_ON(xa, xa_alloc(xa, &id, UINT_MAX, xa_mk_index(id),
+ XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(UINT_MAX),
+ XA_LIMIT(UINT_MAX - 1, UINT_MAX),
GFP_KERNEL) != 0);
XA_BUG_ON(xa, id != 0xffffffffU);
- XA_BUG_ON(xa, xa_alloc(xa, &id, UINT_MAX, xa_mk_index(id),
- GFP_KERNEL) != -ENOSPC);
- XA_BUG_ON(xa, id != 0xffffffffU);
+ id = 3;
+ XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(0),
+ XA_LIMIT(UINT_MAX - 1, UINT_MAX),
+ GFP_KERNEL) != -EBUSY);
+ XA_BUG_ON(xa, id != 3);
xa_destroy(xa);
- id = 10;
- XA_BUG_ON(xa, xa_alloc(xa, &id, 5, xa_mk_index(id),
- GFP_KERNEL) != -ENOSPC);
+ XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(10), XA_LIMIT(10, 5),
+ GFP_KERNEL) != -EBUSY);
XA_BUG_ON(xa, xa_store_index(xa, 3, GFP_KERNEL) != 0);
- XA_BUG_ON(xa, xa_alloc(xa, &id, 5, xa_mk_index(id),
- GFP_KERNEL) != -ENOSPC);
+ XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(10), XA_LIMIT(10, 5),
+ GFP_KERNEL) != -EBUSY);
xa_erase_index(xa, 3);
XA_BUG_ON(xa, !xa_empty(xa));
}
+static noinline void check_xa_alloc_2(struct xarray *xa, unsigned int base)
+{
+ unsigned int i, id;
+ unsigned long index;
+ void *entry;
+
+ /* Allocate and free a NULL and check xa_empty() behaves */
+ XA_BUG_ON(xa, !xa_empty(xa));
+ XA_BUG_ON(xa, xa_alloc(xa, &id, NULL, xa_limit_32b, GFP_KERNEL) != 0);
+ XA_BUG_ON(xa, id != base);
+ XA_BUG_ON(xa, xa_empty(xa));
+ XA_BUG_ON(xa, xa_erase(xa, id) != NULL);
+ XA_BUG_ON(xa, !xa_empty(xa));
+
+ /* Ditto, but check destroy instead of erase */
+ XA_BUG_ON(xa, !xa_empty(xa));
+ XA_BUG_ON(xa, xa_alloc(xa, &id, NULL, xa_limit_32b, GFP_KERNEL) != 0);
+ XA_BUG_ON(xa, id != base);
+ XA_BUG_ON(xa, xa_empty(xa));
+ xa_destroy(xa);
+ XA_BUG_ON(xa, !xa_empty(xa));
+
+ for (i = base; i < base + 10; i++) {
+ XA_BUG_ON(xa, xa_alloc(xa, &id, NULL, xa_limit_32b,
+ GFP_KERNEL) != 0);
+ XA_BUG_ON(xa, id != i);
+ }
+
+ XA_BUG_ON(xa, xa_store(xa, 3, xa_mk_index(3), GFP_KERNEL) != NULL);
+ XA_BUG_ON(xa, xa_store(xa, 4, xa_mk_index(4), GFP_KERNEL) != NULL);
+ XA_BUG_ON(xa, xa_store(xa, 4, NULL, GFP_KERNEL) != xa_mk_index(4));
+ XA_BUG_ON(xa, xa_erase(xa, 5) != NULL);
+ XA_BUG_ON(xa, xa_alloc(xa, &id, NULL, xa_limit_32b, GFP_KERNEL) != 0);
+ XA_BUG_ON(xa, id != 5);
+
+ xa_for_each(xa, index, entry) {
+ xa_erase_index(xa, index);
+ }
+
+ for (i = base; i < base + 9; i++) {
+ XA_BUG_ON(xa, xa_erase(xa, i) != NULL);
+ XA_BUG_ON(xa, xa_empty(xa));
+ }
+ XA_BUG_ON(xa, xa_erase(xa, 8) != NULL);
+ XA_BUG_ON(xa, xa_empty(xa));
+ XA_BUG_ON(xa, xa_erase(xa, base + 9) != NULL);
+ XA_BUG_ON(xa, !xa_empty(xa));
+
+ xa_destroy(xa);
+}
+
static DEFINE_XARRAY_ALLOC(xa0);
static DEFINE_XARRAY_ALLOC1(xa1);
@@ -669,6 +722,8 @@ static noinline void check_xa_alloc(void)
{
check_xa_alloc_1(&xa0, 0);
check_xa_alloc_1(&xa1, 1);
+ check_xa_alloc_2(&xa0, 0);
+ check_xa_alloc_2(&xa1, 1);
}
static noinline void __check_store_iter(struct xarray *xa, unsigned long start,
@@ -1219,9 +1274,8 @@ static void check_align_1(struct xarray *xa, char *name)
void *entry;
for (i = 0; i < 8; i++) {
- id = 0;
- XA_BUG_ON(xa, xa_alloc(xa, &id, UINT_MAX, name + i, GFP_KERNEL)
- != 0);
+ XA_BUG_ON(xa, xa_alloc(xa, &id, name + i, xa_limit_32b,
+ GFP_KERNEL) != 0);
XA_BUG_ON(xa, id != i);
}
xa_for_each(xa, index, entry)
diff --git a/lib/xarray.c b/lib/xarray.c
index 468fb7b..c707388 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1615,23 +1615,23 @@ EXPORT_SYMBOL(xa_store_range);
* __xa_alloc() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
- * @max: Maximum ID to allocate (inclusive).
+ * @limit: Range for allocated ID.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
- * Allocates an unused ID in the range specified by @id and @max.
- * Updates the @id pointer with the index, then stores the entry at that
- * index. A concurrent lookup will not see an uninitialised @id.
+ * Finds an empty entry in @xa between @limit.min and @limit.max,
+ * stores the index into the @id pointer, then stores the entry at
+ * that index. A concurrent lookup will not see an uninitialised @id.
*
* Context: Any context. Expects xa_lock to be held on entry. May
* release and reacquire xa_lock if @gfp flags permit.
- * Return: 0 on success, -ENOMEM if memory allocation fails or -ENOSPC if
- * there is no more space in the XArray.
+ * Return: 0 on success, -ENOMEM if memory could not be allocated or
+ * -EBUSY if there are no free entries in @limit.
*/
-int __xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, gfp_t gfp)
+int __xa_alloc(struct xarray *xa, u32 *id, void *entry,
+ struct xa_limit limit, gfp_t gfp)
{
XA_STATE(xas, xa, 0);
- int err;
if (WARN_ON_ONCE(xa_is_advanced(entry)))
return -EINVAL;
@@ -1642,18 +1642,17 @@ int __xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, gfp_t gfp)
entry = XA_ZERO_ENTRY;
do {
- xas.xa_index = *id;
- xas_find_marked(&xas, max, XA_FREE_MARK);
+ xas.xa_index = limit.min;
+ xas_find_marked(&xas, limit.max, XA_FREE_MARK);
if (xas.xa_node == XAS_RESTART)
- xas_set_err(&xas, -ENOSPC);
+ xas_set_err(&xas, -EBUSY);
+ else
+ *id = xas.xa_index;
xas_store(&xas, entry);
xas_clear_mark(&xas, XA_FREE_MARK);
} while (__xas_nomem(&xas, gfp));
- err = xas_error(&xas);
- if (!err)
- *id = xas.xa_index;
- return err;
+ return xas_error(&xas);
}
EXPORT_SYMBOL(__xa_alloc);