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, 51 insertions, 0 deletions

diff --git a/drivers/hid/hid-keytouch.c b/drivers/hid/hid-keytouch.c
new file mode 100644
index 000000000..b9abd53a5
--- /dev/null
+++ b/drivers/hid/hid-keytouch.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for Keytouch devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2011 Jiri Kosina
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+/* Replace the broken report descriptor of this device with rather
+ * a default one */
+static const __u8 keytouch_fixed_rdesc[] = {
+0x05, 0x01, 0x09, 0x06, 0xa1, 0x01, 0x05, 0x07, 0x19, 0xe0, 0x29, 0xe7, 0x15,
+0x00, 0x25, 0x01, 0x75, 0x01, 0x95, 0x08, 0x81, 0x02, 0x95, 0x01, 0x75, 0x08,
+0x81, 0x01, 0x95, 0x03, 0x75, 0x01, 0x05, 0x08, 0x19, 0x01, 0x29, 0x03, 0x91,
+0x02, 0x95, 0x05, 0x75, 0x01, 0x91, 0x01, 0x95, 0x06, 0x75, 0x08, 0x15, 0x00,
+0x26, 0xff, 0x00, 0x05, 0x07, 0x19, 0x00, 0x2a, 0xff, 0x00, 0x81, 0x00, 0xc0
+};
+
+static const __u8 *keytouch_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	hid_info(hdev, "fixing up Keytouch IEC report descriptor\n");
+
+	*rsize = sizeof(keytouch_fixed_rdesc);
+	return keytouch_fixed_rdesc;
+}
+
+static const struct hid_device_id keytouch_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_KEYTOUCH, USB_DEVICE_ID_KEYTOUCH_IEC) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, keytouch_devices);
+
+static struct hid_driver keytouch_driver = {
+	.name = "keytouch",
+	.id_table = keytouch_devices,
+	.report_fixup = keytouch_report_fixup,
+};
+module_hid_driver(keytouch_driver);
+
+MODULE_DESCRIPTION("HID driver for Keytouch devices not fully compliant with HID standard");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jiri Kosina");