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, 98 insertions, 0 deletions

diff --git a/drivers/hid/hid-generic.c b/drivers/hid/hid-generic.c
new file mode 100644
index 000000000..c2de91674
--- /dev/null
+++ b/drivers/hid/hid-generic.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID support for Linux
+ *
+ *  Copyright (c) 1999 Andreas Gal
+ *  Copyright (c) 2000-2005 Vojtech Pavlik <vojtech@suse.cz>
+ *  Copyright (c) 2005 Michael Haboustak <mike-@cinci.rr.com> for Concept2, Inc
+ *  Copyright (c) 2007-2008 Oliver Neukum
+ *  Copyright (c) 2006-2012 Jiri Kosina
+ *  Copyright (c) 2012 Henrik Rydberg
+ */
+
+/*
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/unaligned.h>
+#include <asm/byteorder.h>
+
+#include <linux/hid.h>
+
+static struct hid_driver hid_generic;
+
+static int __check_hid_generic(struct device_driver *drv, void *data)
+{
+	struct hid_driver *hdrv = to_hid_driver(drv);
+	struct hid_device *hdev = data;
+
+	if (hdrv == &hid_generic)
+		return 0;
+
+	return hid_match_device(hdev, hdrv) != NULL;
+}
+
+static bool hid_generic_match(struct hid_device *hdev,
+			      bool ignore_special_driver)
+{
+	if (ignore_special_driver)
+		return true;
+
+	if (hdev->quirks & HID_QUIRK_IGNORE_SPECIAL_DRIVER)
+		return true;
+
+	if (hdev->quirks & HID_QUIRK_HAVE_SPECIAL_DRIVER)
+		return false;
+
+	/*
+	 * If any other driver wants the device, leave the device to this other
+	 * driver.
+	 */
+	if (bus_for_each_drv(&hid_bus_type, NULL, hdev, __check_hid_generic))
+		return false;
+
+	return true;
+}
+
+static int hid_generic_probe(struct hid_device *hdev,
+			     const struct hid_device_id *id)
+{
+	int ret;
+
+	hdev->quirks |= HID_QUIRK_INPUT_PER_APP;
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return ret;
+
+	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+}
+
+static int hid_generic_reset_resume(struct hid_device *hdev)
+{
+	if (hdev->claimed & HID_CLAIMED_INPUT)
+		hidinput_reset_resume(hdev);
+
+	return 0;
+}
+
+static const struct hid_device_id hid_table[] = {
+	{ HID_DEVICE(HID_BUS_ANY, HID_GROUP_ANY, HID_ANY_ID, HID_ANY_ID) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, hid_table);
+
+static struct hid_driver hid_generic = {
+	.name = "hid-generic",
+	.id_table = hid_table,
+	.match = hid_generic_match,
+	.probe = hid_generic_probe,
+	.reset_resume = hid_generic_reset_resume,
+};
+module_hid_driver(hid_generic);
+
+MODULE_AUTHOR("Henrik Rydberg");
+MODULE_DESCRIPTION("HID generic driver");
+MODULE_LICENSE("GPL");