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, 97 insertions, 0 deletions

diff --git a/drivers/input/misc/ad714x-i2c.c b/drivers/input/misc/ad714x-i2c.c
new file mode 100644
index 000000000..c3cb56151
--- /dev/null
+++ b/drivers/input/misc/ad714x-i2c.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD714X CapTouch Programmable Controller driver (I2C bus)
+ *
+ * Copyright 2009-2011 Analog Devices Inc.
+ */
+
+#include <linux/input.h>	/* BUS_I2C */
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/pm.h>
+#include "ad714x.h"
+
+static int ad714x_i2c_write(struct ad714x_chip *chip,
+			    unsigned short reg, unsigned short data)
+{
+	struct i2c_client *client = to_i2c_client(chip->dev);
+	int error;
+
+	chip->xfer_buf[0] = cpu_to_be16(reg);
+	chip->xfer_buf[1] = cpu_to_be16(data);
+
+	error = i2c_master_send(client, (u8 *)chip->xfer_buf,
+				2 * sizeof(*chip->xfer_buf));
+	if (unlikely(error < 0)) {
+		dev_err(&client->dev, "I2C write error: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static int ad714x_i2c_read(struct ad714x_chip *chip,
+			   unsigned short reg, unsigned short *data, size_t len)
+{
+	struct i2c_client *client = to_i2c_client(chip->dev);
+	int i;
+	int error;
+
+	chip->xfer_buf[0] = cpu_to_be16(reg);
+
+	error = i2c_master_send(client, (u8 *)chip->xfer_buf,
+				sizeof(*chip->xfer_buf));
+	if (error >= 0)
+		error = i2c_master_recv(client, (u8 *)chip->xfer_buf,
+					len * sizeof(*chip->xfer_buf));
+
+	if (unlikely(error < 0)) {
+		dev_err(&client->dev, "I2C read error: %d\n", error);
+		return error;
+	}
+
+	for (i = 0; i < len; i++)
+		data[i] = be16_to_cpu(chip->xfer_buf[i]);
+
+	return 0;
+}
+
+static int ad714x_i2c_probe(struct i2c_client *client)
+{
+	struct ad714x_chip *chip;
+
+	chip = ad714x_probe(&client->dev, BUS_I2C, client->irq,
+			    ad714x_i2c_read, ad714x_i2c_write);
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+
+	i2c_set_clientdata(client, chip);
+
+	return 0;
+}
+
+static const struct i2c_device_id ad714x_id[] = {
+	{ .name = "ad7142_captouch" },
+	{ .name = "ad7143_captouch" },
+	{ .name = "ad7147_captouch" },
+	{ .name = "ad7147a_captouch" },
+	{ .name = "ad7148_captouch" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ad714x_id);
+
+static struct i2c_driver ad714x_i2c_driver = {
+	.driver = {
+		.name = "ad714x_captouch",
+		.pm   = pm_sleep_ptr(&ad714x_pm),
+	},
+	.probe = ad714x_i2c_probe,
+	.id_table = ad714x_id,
+};
+
+module_i2c_driver(ad714x_i2c_driver);
+
+MODULE_DESCRIPTION("Analog Devices AD714X Capacitance Touch Sensor I2C Bus Driver");
+MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");
+MODULE_LICENSE("GPL");