[PATCH v2 0/2] test_xarray: advanced API multi-index tests

[PATCH v2 0/2] test_xarray: advanced API multi-index tests

[Luis Chamberlain]

This is a respin of the test_xarray multi-index tests [0] which use and
demonstrate the advanced API which is used by the page cache. This should
let folks more easily follow how we use multi-index to support for example
a min order later in the page cache. It also lets us grow the selftests to
mimic more of what we do in the page cache.

Changes since v1:

  - Fixed RCU stall, the issue was the misssing RCU locks when fetching
    an entry, so we now add test_get_entry() which mimics filemap_get_entry() 
  - Provide a bit more comments
  - Check for alignment on the index to the order on
    check_xa_multi_store_adv_add()
  - Use a helper check_xa_multi_store_adv_del_entry() to mimic what
    we do in page_cache_delete()

Changes since RFC:

  - Moved out from tmpfs large folio patches [1] so to keep these patches
    separate
  - Update cmpxchg test to include another entry at 1 << order that
    'keeps' the node around and order information.
  - Update cmpxchg test to verify the entries and order in all tied
    indexes.
  - Drop previous Luis Chamberlain's review as changes are significant
    from the RFC.

[0] https://lkml.kernel.org/r/20231104005747.1389762-1-da.gomez@samsung.com
[1] https://lore.kernel.org/all/20231028211518.3424020-1-da.gomez@samsung.com/

Daniel Gomez (1):
  XArray: add cmpxchg order test

Luis Chamberlain (1):
  test_xarray: add tests for advanced multi-index use

 lib/test_xarray.c | 218 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 218 insertions(+)

-- 
2.43.0

[PATCH v2 1/2] test_xarray: add tests for advanced multi-index use

[Luis Chamberlain]

The multi index selftests are great but they don't replicate
how we deal with the page cache exactly, which makes it a bit
hard to follow as the page cache uses the advanced API.

Add tests which use the advanced API, mimicking what we do in the
page cache, while at it, extend the example to do what is needed for
min order support.

Tested-by: Daniel Gomez <da.gomez@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 lib/test_xarray.c | 164 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 164 insertions(+)

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index e77d4856442c..8b23481f0e8f 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -674,6 +674,169 @@ static noinline void check_multi_store(struct xarray *xa)
 #endif
 }
 
+#ifdef CONFIG_XARRAY_MULTI
+/* mimics page cache __filemap_add_folio() */
+static noinline void check_xa_multi_store_adv_add(struct xarray *xa,
+						  unsigned long index,
+						  unsigned int order,
+						  void *p)
+{
+	XA_STATE(xas, xa, index);
+	unsigned int nrpages = 1UL << order;
+
+	/* users are responsible for index alignemnt to the order when adding */
+	XA_BUG_ON(xa, index & (nrpages - 1));
+
+	xas_set_order(&xas, index, order);
+
+	do {
+		xas_lock_irq(&xas);
+
+		xas_store(&xas, p);
+		XA_BUG_ON(xa, xas_error(&xas));
+		XA_BUG_ON(xa, xa_load(xa, index) != p);
+
+		xas_unlock_irq(&xas);
+	} while (xas_nomem(&xas, GFP_KERNEL));
+
+	XA_BUG_ON(xa, xas_error(&xas));
+}
+
+/* mimics page_cache_delete() */
+static noinline void check_xa_multi_store_adv_del_entry(struct xarray *xa,
+							unsigned long index,
+							unsigned int order)
+{
+	XA_STATE(xas, xa, index);
+
+	xas_set_order(&xas, index, order);
+	xas_store(&xas, NULL);
+	xas_init_marks(&xas);
+}
+
+static noinline void check_xa_multi_store_adv_delete(struct xarray *xa,
+						     unsigned long index,
+						     unsigned int order)
+{
+	xa_lock_irq(xa);
+	check_xa_multi_store_adv_del_entry(xa, index, order);
+	xa_unlock_irq(xa);
+}
+
+/* mimics page cache filemap_get_entry() */
+static noinline void *test_get_entry(struct xarray *xa, unsigned long index)
+{
+	XA_STATE(xas, xa, index);
+	void *p;
+
+	rcu_read_lock();
+repeat:
+	xas_reset(&xas);
+	p = xas_load(&xas);
+	if (xas_retry(&xas, p))
+		goto repeat;
+	rcu_read_unlock();
+
+	return p;
+}
+
+static unsigned long some_val = 0xdeadbeef;
+static unsigned long some_val_2 = 0xdeaddead;
+
+/* mimics the page cache usage */
+static noinline void check_xa_multi_store_adv(struct xarray *xa,
+					      unsigned long pos,
+					      unsigned int order)
+{
+	unsigned int nrpages = 1UL << order;
+	unsigned long index, base, next_index, next_next_index;
+	unsigned int i;
+
+	index = pos >> PAGE_SHIFT;
+	base = round_down(index, nrpages);
+	next_index = round_down(base + nrpages, nrpages);
+	next_next_index = round_down(next_index + nrpages, nrpages);
+
+	check_xa_multi_store_adv_add(xa, base, order, &some_val);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, base + i) != &some_val);
+
+	XA_BUG_ON(xa, test_get_entry(xa, next_index) != NULL);
+
+	/* Use order 0 for the next item */
+	check_xa_multi_store_adv_add(xa, next_index, 0, &some_val_2);
+	XA_BUG_ON(xa, test_get_entry(xa, next_index) != &some_val_2);
+
+	/* Remove the next item */
+	check_xa_multi_store_adv_delete(xa, next_index, 0);
+
+	/* Now use order for a new pointer */
+	check_xa_multi_store_adv_add(xa, next_index, order, &some_val_2);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, next_index + i) != &some_val_2);
+
+	check_xa_multi_store_adv_delete(xa, next_index, order);
+	check_xa_multi_store_adv_delete(xa, base, order);
+	XA_BUG_ON(xa, !xa_empty(xa));
+
+	/* starting fresh again */
+
+	/* let's test some holes now */
+
+	/* hole at base and next_next */
+	check_xa_multi_store_adv_add(xa, next_index, order, &some_val_2);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, base + i) != NULL);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, next_index + i) != &some_val_2);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, next_next_index + i) != NULL);
+
+	check_xa_multi_store_adv_delete(xa, next_index, order);
+	XA_BUG_ON(xa, !xa_empty(xa));
+
+	/* hole at base and next */
+
+	check_xa_multi_store_adv_add(xa, next_next_index, order, &some_val_2);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, base + i) != NULL);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, next_index + i) != NULL);
+
+	for (i = 0; i < nrpages; i++)
+		XA_BUG_ON(xa, test_get_entry(xa, next_next_index + i) != &some_val_2);
+
+	check_xa_multi_store_adv_delete(xa, next_next_index, order);
+	XA_BUG_ON(xa, !xa_empty(xa));
+}
+#endif
+
+static noinline void check_multi_store_advanced(struct xarray *xa)
+{
+#ifdef CONFIG_XARRAY_MULTI
+	unsigned int max_order = IS_ENABLED(CONFIG_XARRAY_MULTI) ? 20 : 1;
+	unsigned long end = ULONG_MAX/2;
+	unsigned long pos, i;
+
+	/*
+	 * About 117 million tests below.
+	 */
+	for (pos = 7; pos < end; pos = (pos * pos) + 564) {
+		for (i = 0; i < max_order; i++) {
+			check_xa_multi_store_adv(xa, pos, i);
+			check_xa_multi_store_adv(xa, pos + 157, i);
+		}
+	}
+#endif
+}
+
 static noinline void check_xa_alloc_1(struct xarray *xa, unsigned int base)
 {
 	int i;
@@ -1804,6 +1967,7 @@ static int xarray_checks(void)
 	check_reserve(&array);
 	check_reserve(&xa0);
 	check_multi_store(&array);
+	check_multi_store_advanced(&array);
 	check_get_order(&array);
 	check_xa_alloc();
 	check_find(&array);
-- 
2.43.0

[PATCH v2 2/2] XArray: add cmpxchg order test

[Luis Chamberlain]

From: Daniel Gomez <da.gomez@samsung.com>

XArray multi-index entries do not keep track of the order stored once
the entry is being marked as used with cmpxchg (conditionally replaced
with NULL). Add a test to check the order is actually lost. The test
also verifies the order and entries for all the tied indexes before and
after the NULL replacement with xa_cmpxchg.

Add another entry at 1 << order that keeps the node around and the order
information for the NULL-entry after xa_cmpxchg.

Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 lib/test_xarray.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 8b23481f0e8f..d4e55b4867dc 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -423,6 +423,59 @@ static noinline void check_cmpxchg(struct xarray *xa)
 	XA_BUG_ON(xa, !xa_empty(xa));
 }
 
+static noinline void check_cmpxchg_order(struct xarray *xa)
+{
+#ifdef CONFIG_XARRAY_MULTI
+	void *FIVE = xa_mk_value(5);
+	unsigned int i, order = 3;
+
+	XA_BUG_ON(xa, xa_store_order(xa, 0, order, FIVE, GFP_KERNEL));
+
+	/* Check entry FIVE has the order saved */
+	XA_BUG_ON(xa, xa_get_order(xa, xa_to_value(FIVE)) != order);
+
+	/* Check all the tied indexes have the same entry and order */
+	for (i = 0; i < (1 << order); i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != FIVE);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != order);
+	}
+
+	/* Ensure that nothing is stored at index '1 << order' */
+	XA_BUG_ON(xa, xa_load(xa, 1 << order) != NULL);
+
+	/*
+	 * Additionally, keep the node information and the order at
+	 * '1 << order'
+	 */
+	XA_BUG_ON(xa, xa_store_order(xa, 1 << order, order, FIVE, GFP_KERNEL));
+	for (i = (1 << order); i < (1 << order) + (1 << order) - 1; i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != FIVE);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != order);
+	}
+
+	/* Conditionally replace FIVE entry at index '0' with NULL */
+	XA_BUG_ON(xa, xa_cmpxchg(xa, 0, FIVE, NULL, GFP_KERNEL) != FIVE);
+
+	/* Verify the order is lost at FIVE (and old) entries */
+	XA_BUG_ON(xa, xa_get_order(xa, xa_to_value(FIVE)) != 0);
+
+	/* Verify the order and entries are lost in all the tied indexes */
+	for (i = 0; i < (1 << order); i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != NULL);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != 0);
+	}
+
+	/* Verify node and order are kept at '1 << order' */
+	for (i = (1 << order); i < (1 << order) + (1 << order) - 1; i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != FIVE);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != order);
+	}
+
+	xa_store_order(xa, 0, BITS_PER_LONG - 1, NULL, GFP_KERNEL);
+	XA_BUG_ON(xa, !xa_empty(xa));
+#endif
+}
+
 static noinline void check_reserve(struct xarray *xa)
 {
 	void *entry;
@@ -1964,6 +2017,7 @@ static int xarray_checks(void)
 	check_xas_erase(&array);
 	check_insert(&array);
 	check_cmpxchg(&array);
+	check_cmpxchg_order(&array);
 	check_reserve(&array);
 	check_reserve(&xa0);
 	check_multi_store(&array);
-- 
2.43.0