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xarray: Add xa_reserve and xa_release

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This function reserves a slot in the XArray for users which need
to acquire multiple locks before storing their entry in the tree and
so cannot use a plain xa_store().

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox
2018-10-01 14:54:59 -04:00
parent 2264f5132f
commit 9f14d4f1f1
4 changed files with 125 additions and 2 deletions
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40
lib/test_xarray.c
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@@ -259,6 +259,45 @@ static noinline void check_cmpxchg(struct xarray *xa)
XA_BUG_ON(xa, !xa_empty(xa));
}
static noinline void check_reserve(struct xarray *xa)
{
void *entry;
unsigned long index = 0;
/* An array with a reserved entry is not empty */
XA_BUG_ON(xa, !xa_empty(xa));
xa_reserve(xa, 12345678, GFP_KERNEL);
XA_BUG_ON(xa, xa_empty(xa));
XA_BUG_ON(xa, xa_load(xa, 12345678));
xa_release(xa, 12345678);
XA_BUG_ON(xa, !xa_empty(xa));
/* Releasing a used entry does nothing */
xa_reserve(xa, 12345678, GFP_KERNEL);
XA_BUG_ON(xa, xa_store_index(xa, 12345678, GFP_NOWAIT) != NULL);
xa_release(xa, 12345678);
xa_erase_index(xa, 12345678);
XA_BUG_ON(xa, !xa_empty(xa));
/* cmpxchg sees a reserved entry as NULL */
xa_reserve(xa, 12345678, GFP_KERNEL);
XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, NULL, xa_mk_value(12345678),
GFP_NOWAIT) != NULL);
xa_release(xa, 12345678);
xa_erase_index(xa, 12345678);
XA_BUG_ON(xa, !xa_empty(xa));
/* Can iterate through a reserved entry */
xa_store_index(xa, 5, GFP_KERNEL);
xa_reserve(xa, 6, GFP_KERNEL);
xa_store_index(xa, 7, GFP_KERNEL);
xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {
XA_BUG_ON(xa, index != 5 && index != 7);
}
xa_destroy(xa);
}
static noinline void check_xas_erase(struct xarray *xa)
{
XA_STATE(xas, xa, 0);
@@ -808,6 +847,7 @@ static int xarray_checks(void)
check_xa_shrink(&array);
check_xas_erase(&array);
check_cmpxchg(&array);
check_reserve(&array);
check_multi_store(&array);
check_find(&array);
check_destroy(&array);