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, 153 insertions, 0 deletions

diff --git a/drivers/input/mouse/maplemouse.c b/drivers/input/mouse/maplemouse.c
new file mode 100644
index 000000000..0c8f7d1b0
--- /dev/null
+++ b/drivers/input/mouse/maplemouse.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *	SEGA Dreamcast mouse driver
+ *	Based on drivers/usb/usbmouse.c
+ *
+ *	Copyright (c) Yaegashi Takeshi, 2001
+ *	Copyright (c) Adrian McMenamin, 2008 - 2009
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/timer.h>
+#include <linux/maple.h>
+
+MODULE_AUTHOR("Adrian McMenamin <adrian@mcmen.demon.co.uk>");
+MODULE_DESCRIPTION("SEGA Dreamcast mouse driver");
+MODULE_LICENSE("GPL");
+
+struct dc_mouse {
+	struct input_dev *dev;
+	struct maple_device *mdev;
+};
+
+static void dc_mouse_callback(struct mapleq *mq)
+{
+	int buttons, relx, rely, relz;
+	struct maple_device *mapledev = mq->dev;
+	struct dc_mouse *mse = maple_get_drvdata(mapledev);
+	struct input_dev *dev = mse->dev;
+	unsigned char *res = mq->recvbuf->buf;
+
+	buttons = ~res[8];
+	relx = *(unsigned short *)(res + 12) - 512;
+	rely = *(unsigned short *)(res + 14) - 512;
+	relz = *(unsigned short *)(res + 16) - 512;
+
+	input_report_key(dev, BTN_LEFT,   buttons & 4);
+	input_report_key(dev, BTN_MIDDLE, buttons & 9);
+	input_report_key(dev, BTN_RIGHT,  buttons & 2);
+	input_report_rel(dev, REL_X,      relx);
+	input_report_rel(dev, REL_Y,      rely);
+	input_report_rel(dev, REL_WHEEL,  relz);
+	input_sync(dev);
+}
+
+static int dc_mouse_open(struct input_dev *dev)
+{
+	struct dc_mouse *mse = input_get_drvdata(dev);
+
+	maple_getcond_callback(mse->mdev, dc_mouse_callback, HZ/50,
+		MAPLE_FUNC_MOUSE);
+
+	return 0;
+}
+
+static void dc_mouse_close(struct input_dev *dev)
+{
+	struct dc_mouse *mse = input_get_drvdata(dev);
+
+	maple_getcond_callback(mse->mdev, dc_mouse_callback, 0,
+		MAPLE_FUNC_MOUSE);
+}
+
+/* allow the mouse to be used */
+static int probe_maple_mouse(struct device *dev)
+{
+	struct maple_device *mdev = to_maple_dev(dev);
+	struct maple_driver *mdrv = to_maple_driver(dev->driver);
+	int error;
+	struct input_dev *input_dev;
+	struct dc_mouse *mse;
+
+	mse = kzalloc_obj(*mse);
+	if (!mse) {
+		error = -ENOMEM;
+		goto fail;
+	}
+
+	input_dev = input_allocate_device();
+	if (!input_dev) {
+		error = -ENOMEM;
+		goto fail_nomem;
+	}
+
+	mse->dev = input_dev;
+	mse->mdev = mdev;
+
+	maple_set_drvdata(mdev, mse);
+
+	input_set_drvdata(input_dev, mse);
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+	input_dev->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_LEFT) |
+		BIT_MASK(BTN_RIGHT) | BIT_MASK(BTN_MIDDLE);
+	input_dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y) |
+		BIT_MASK(REL_WHEEL);
+	input_dev->open = dc_mouse_open;
+	input_dev->close = dc_mouse_close;
+	input_dev->name = mdev->product_name;
+	input_dev->id.bustype = BUS_HOST;
+	error =	input_register_device(input_dev);
+	if (error)
+		goto fail_register;
+
+	mdev->driver = mdrv;
+
+	return error;
+
+fail_register:
+	input_free_device(input_dev);
+	maple_set_drvdata(mdev, NULL);
+fail_nomem:
+	kfree(mse);
+fail:
+	return error;
+}
+
+static int remove_maple_mouse(struct device *dev)
+{
+	struct maple_device *mdev = to_maple_dev(dev);
+	struct dc_mouse *mse = maple_get_drvdata(mdev);
+
+	mdev->callback = NULL;
+	input_unregister_device(mse->dev);
+	maple_set_drvdata(mdev, NULL);
+	kfree(mse);
+
+	return 0;
+}
+
+static struct maple_driver dc_mouse_driver = {
+	.function =	MAPLE_FUNC_MOUSE,
+	.drv = {
+		.name = "Dreamcast_mouse",
+		.probe = probe_maple_mouse,
+		.remove = remove_maple_mouse,
+	},
+};
+
+static int __init dc_mouse_init(void)
+{
+	return maple_driver_register(&dc_mouse_driver);
+}
+
+static void __exit dc_mouse_exit(void)
+{
+	maple_driver_unregister(&dc_mouse_driver);
+}
+
+module_init(dc_mouse_init);
+module_exit(dc_mouse_exit);