netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 120 insertions, 0 deletions

diff --git a/drivers/of/overlay_test.c b/drivers/of/overlay_test.c
new file mode 100644
index 000000000..c787524c5
--- /dev/null
+++ b/drivers/of/overlay_test.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for device tree overlays
+ */
+#include <linux/device/bus.h>
+#include <linux/kconfig.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+
+#include <kunit/of.h>
+#include <kunit/test.h>
+
+#include "of_private.h"
+
+static const char * const kunit_node_name = "kunit-test";
+static const char * const kunit_compatible = "test,empty";
+
+/* Test that of_overlay_apply_kunit() adds a node to the live tree */
+static void of_overlay_apply_kunit_apply(struct kunit *test)
+{
+	struct device_node *np;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			of_overlay_apply_kunit(test, kunit_overlay_test));
+
+	np = of_find_node_by_name(NULL, kunit_node_name);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, np);
+	of_node_put(np);
+}
+
+/*
+ * Test that of_overlay_apply_kunit() creates platform devices with the
+ * expected device_node
+ */
+static void of_overlay_apply_kunit_platform_device(struct kunit *test)
+{
+	struct platform_device *pdev;
+	struct device_node *np;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			of_overlay_apply_kunit(test, kunit_overlay_test));
+
+	np = of_find_node_by_name(NULL, kunit_node_name);
+	of_node_put_kunit(test, np);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, np);
+
+	pdev = of_find_device_by_node(np);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, pdev);
+	if (pdev)
+		put_device(&pdev->dev);
+}
+
+static int of_overlay_bus_match_compatible(struct device *dev, const void *data)
+{
+	return of_device_is_compatible(dev->of_node, data);
+}
+
+/* Test that of_overlay_apply_kunit() cleans up after the test is finished */
+static void of_overlay_apply_kunit_cleanup(struct kunit *test)
+{
+	struct kunit fake;
+	struct platform_device *pdev;
+	struct device *dev;
+	struct device_node *np;
+
+	of_root_kunit_skip(test);
+	if (!IS_ENABLED(CONFIG_OF_OVERLAY))
+		kunit_skip(test, "requires CONFIG_OF_OVERLAY to apply overlay");
+	if (!IS_ENABLED(CONFIG_OF_EARLY_FLATTREE))
+		kunit_skip(test, "requires CONFIG_OF_EARLY_FLATTREE for root node");
+
+	kunit_init_test(&fake, "fake test", NULL);
+	KUNIT_ASSERT_EQ(test, fake.status, KUNIT_SUCCESS);
+
+	KUNIT_ASSERT_EQ(test, 0,
+			of_overlay_apply_kunit(&fake, kunit_overlay_test));
+
+	np = of_find_node_by_name(NULL, kunit_node_name);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, np);
+	of_node_put_kunit(&fake, np);
+
+	pdev = of_find_device_by_node(np);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+	put_device(&pdev->dev); /* Not derefing 'pdev' after this */
+
+	/* Remove overlay */
+	kunit_cleanup(&fake);
+
+	/* The node and device should be removed */
+	np = of_find_node_by_name(NULL, kunit_node_name);
+	KUNIT_EXPECT_PTR_EQ(test, NULL, np);
+	of_node_put(np);
+
+	dev = bus_find_device(&platform_bus_type, NULL, kunit_compatible,
+			      of_overlay_bus_match_compatible);
+	KUNIT_EXPECT_PTR_EQ(test, NULL, dev);
+	put_device(dev);
+}
+
+static struct kunit_case of_overlay_apply_kunit_test_cases[] = {
+	KUNIT_CASE(of_overlay_apply_kunit_apply),
+	KUNIT_CASE(of_overlay_apply_kunit_platform_device),
+	KUNIT_CASE(of_overlay_apply_kunit_cleanup),
+	{}
+};
+
+/*
+ * Test suite for test managed device tree overlays.
+ */
+static struct kunit_suite of_overlay_apply_kunit_suite = {
+	.name = "of_overlay_apply_kunit",
+	.test_cases = of_overlay_apply_kunit_test_cases,
+};
+
+kunit_test_suites(
+	&of_overlay_apply_kunit_suite,
+);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KUnit tests for device tree overlays");