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, 117 insertions, 0 deletions

diff --git a/drivers/acpi/container.c b/drivers/acpi/container.c
new file mode 100644
index 000000000..f138a4335
--- /dev/null
+++ b/drivers/acpi/container.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * container.c  - ACPI Generic Container Driver
+ *
+ * Copyright (C) 2004 Anil S Keshavamurthy (anil.s.keshavamurthy@intel.com)
+ * Copyright (C) 2004 Keiichiro Tokunaga (tokunaga.keiich@jp.fujitsu.com)
+ * Copyright (C) 2004 Motoyuki Ito (motoyuki@soft.fujitsu.com)
+ * Copyright (C) 2004 FUJITSU LIMITED
+ * Copyright (C) 2004, 2013 Intel Corp.
+ * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+ */
+#include <linux/acpi.h>
+#include <linux/container.h>
+
+#include "internal.h"
+
+static const struct acpi_device_id container_device_ids[] = {
+	{"ACPI0004", 0},
+	{"PNP0A05", 0},
+	{"PNP0A06", 0},
+	{"", 0},
+};
+
+#ifdef CONFIG_ACPI_CONTAINER
+
+static int check_offline(struct acpi_device *adev, void *not_used)
+{
+	if (acpi_scan_is_offline(adev, false))
+		return 0;
+
+	return -EBUSY;
+}
+
+static int acpi_container_offline(struct container_dev *cdev)
+{
+	/* Check all of the dependent devices' physical companions. */
+	return acpi_dev_for_each_child(ACPI_COMPANION(&cdev->dev), check_offline, NULL);
+}
+
+static void acpi_container_release(struct device *dev)
+{
+	kfree(to_container_dev(dev));
+}
+
+static int container_device_attach(struct acpi_device *adev,
+				   const struct acpi_device_id *not_used)
+{
+	struct container_dev *cdev;
+	struct device *dev;
+	int ret;
+
+	if (adev->flags.is_dock_station)
+		return 0;
+
+	cdev = kzalloc_obj(*cdev);
+	if (!cdev)
+		return -ENOMEM;
+
+	cdev->offline = acpi_container_offline;
+	dev = &cdev->dev;
+	dev->bus = &container_subsys;
+	dev_set_name(dev, "%s", dev_name(&adev->dev));
+	ACPI_COMPANION_SET(dev, adev);
+	dev->release = acpi_container_release;
+	ret = device_register(dev);
+	if (ret) {
+		put_device(dev);
+		return ret;
+	}
+	adev->driver_data = dev;
+	return 1;
+}
+
+static void container_device_detach(struct acpi_device *adev)
+{
+	struct device *dev = acpi_driver_data(adev);
+
+	adev->driver_data = NULL;
+	if (dev)
+		device_unregister(dev);
+}
+
+static void container_device_online(struct acpi_device *adev)
+{
+	struct device *dev = acpi_driver_data(adev);
+
+	kobject_uevent(&dev->kobj, KOBJ_ONLINE);
+}
+
+static struct acpi_scan_handler container_handler = {
+	.ids = container_device_ids,
+	.attach = container_device_attach,
+	.detach = container_device_detach,
+	.hotplug = {
+		.enabled = true,
+		.demand_offline = true,
+		.notify_online = container_device_online,
+	},
+};
+
+void __init acpi_container_init(void)
+{
+	acpi_scan_add_handler(&container_handler);
+}
+
+#else
+
+static struct acpi_scan_handler container_handler = {
+	.ids = container_device_ids,
+};
+
+void __init acpi_container_init(void)
+{
+	acpi_scan_add_handler_with_hotplug(&container_handler, "container");
+}
+
+#endif /* CONFIG_ACPI_CONTAINER */