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, 341 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-bq32k.c b/drivers/rtc/rtc-bq32k.c
new file mode 100644
index 000000000..573231613
--- /dev/null
+++ b/drivers/rtc/rtc-bq32k.c
@@ -0,0 +1,341 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for TI BQ32000 RTC.
+ *
+ * Copyright (C) 2009 Semihalf.
+ * Copyright (C) 2014 Pavel Machek <pavel@denx.de>
+ *
+ * You can get hardware description at
+ * https://www.ti.com/lit/ds/symlink/bq32000.pdf
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/init.h>
+#include <linux/kstrtox.h>
+#include <linux/errno.h>
+#include <linux/bcd.h>
+#include <linux/delay.h>
+
+#define BQ32K_SECONDS		0x00	/* Seconds register address */
+#define BQ32K_SECONDS_MASK	0x7F	/* Mask over seconds value */
+#define BQ32K_STOP		0x80	/* Oscillator Stop flat */
+
+#define BQ32K_MINUTES		0x01	/* Minutes register address */
+#define BQ32K_MINUTES_MASK	0x7F	/* Mask over minutes value */
+#define BQ32K_OF		0x80	/* Oscillator Failure flag */
+
+#define BQ32K_HOURS_MASK	0x3F	/* Mask over hours value */
+#define BQ32K_CENT		0x40	/* Century flag */
+#define BQ32K_CENT_EN		0x80	/* Century flag enable bit */
+
+#define BQ32K_CALIBRATION	0x07	/* CAL_CFG1, calibration and control */
+#define BQ32K_TCH2		0x08	/* Trickle charge enable */
+#define BQ32K_CFG2		0x09	/* Trickle charger control */
+#define BQ32K_TCFE		BIT(6)	/* Trickle charge FET bypass */
+
+#define MAX_LEN			10	/* Maximum number of consecutive
+					 * register for this particular RTC.
+					 */
+
+struct bq32k_regs {
+	uint8_t		seconds;
+	uint8_t		minutes;
+	uint8_t		cent_hours;
+	uint8_t		day;
+	uint8_t		date;
+	uint8_t		month;
+	uint8_t		years;
+};
+
+static struct i2c_driver bq32k_driver;
+
+static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct i2c_msg msgs[] = {
+		{
+			.addr = client->addr,
+			.flags = 0,
+			.len = 1,
+			.buf = &off,
+		}, {
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = len,
+			.buf = data,
+		}
+	};
+
+	if (i2c_transfer(client->adapter, msgs, 2) == 2)
+		return 0;
+
+	return -EIO;
+}
+
+static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	uint8_t buffer[MAX_LEN + 1];
+
+	buffer[0] = off;
+	memcpy(&buffer[1], data, len);
+
+	if (i2c_master_send(client, buffer, len + 1) == len + 1)
+		return 0;
+
+	return -EIO;
+}
+
+static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct bq32k_regs regs;
+	int error;
+
+	/*
+	 * When the device doesn't have the interrupt connected, prevent
+	 * userpace from polling the RTC registers too frequently.
+	 */
+	if (client->irq <= 0)
+		usleep_range(2000, 2500);
+
+	error = bq32k_read(dev, &regs, 0, sizeof(regs));
+	if (error)
+		return error;
+
+	/*
+	 * In case of oscillator failure, the register contents should be
+	 * considered invalid. The flag is cleared the next time the RTC is set.
+	 */
+	if (regs.minutes & BQ32K_OF)
+		return -EINVAL;
+
+	tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
+	tm->tm_min = bcd2bin(regs.minutes & BQ32K_MINUTES_MASK);
+	tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
+	tm->tm_mday = bcd2bin(regs.date);
+	tm->tm_wday = bcd2bin(regs.day) - 1;
+	tm->tm_mon = bcd2bin(regs.month) - 1;
+	tm->tm_year = bcd2bin(regs.years) +
+				((regs.cent_hours & BQ32K_CENT) ? 100 : 0);
+
+	return 0;
+}
+
+static int bq32k_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bq32k_regs regs;
+
+	regs.seconds = bin2bcd(tm->tm_sec);
+	regs.minutes = bin2bcd(tm->tm_min);
+	regs.cent_hours = bin2bcd(tm->tm_hour) | BQ32K_CENT_EN;
+	regs.day = bin2bcd(tm->tm_wday + 1);
+	regs.date = bin2bcd(tm->tm_mday);
+	regs.month = bin2bcd(tm->tm_mon + 1);
+
+	if (tm->tm_year >= 100) {
+		regs.cent_hours |= BQ32K_CENT;
+		regs.years = bin2bcd(tm->tm_year - 100);
+	} else
+		regs.years = bin2bcd(tm->tm_year);
+
+	return bq32k_write(dev, &regs, 0, sizeof(regs));
+}
+
+static const struct rtc_class_ops bq32k_rtc_ops = {
+	.read_time	= bq32k_rtc_read_time,
+	.set_time	= bq32k_rtc_set_time,
+};
+
+static int trickle_charger_of_init(struct device *dev, struct device_node *node)
+{
+	unsigned char reg;
+	int error;
+	u32 ohms = 0;
+
+	if (of_property_read_u32(node, "trickle-resistor-ohms" , &ohms))
+		return 0;
+
+	switch (ohms) {
+	case 180+940:
+		/*
+		 * TCHE[3:0] == 0x05, TCH2 == 1, TCFE == 0 (charging
+		 * over diode and 940ohm resistor)
+		 */
+
+		if (of_property_read_bool(node, "trickle-diode-disable")) {
+			dev_err(dev, "diode and resistor mismatch\n");
+			return -EINVAL;
+		}
+		reg = 0x05;
+		break;
+
+	case 180+20000:
+		/* diode disabled */
+
+		if (!of_property_read_bool(node, "trickle-diode-disable")) {
+			dev_err(dev, "bq32k: diode and resistor mismatch\n");
+			return -EINVAL;
+		}
+		reg = 0x45;
+		break;
+
+	default:
+		dev_err(dev, "invalid resistor value (%d)\n", ohms);
+		return -EINVAL;
+	}
+
+	error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
+	if (error)
+		return error;
+
+	reg = 0x20;
+	error = bq32k_write(dev, &reg, BQ32K_TCH2, 1);
+	if (error)
+		return error;
+
+	dev_info(dev, "Enabled trickle RTC battery charge.\n");
+	return 0;
+}
+
+static ssize_t bq32k_sysfs_show_tricklecharge_bypass(struct device *dev,
+					       struct device_attribute *attr,
+					       char *buf)
+{
+	int reg, error;
+
+	error = bq32k_read(dev, &reg, BQ32K_CFG2, 1);
+	if (error)
+		return error;
+
+	return sprintf(buf, "%d\n", (reg & BQ32K_TCFE) ? 1 : 0);
+}
+
+static ssize_t bq32k_sysfs_store_tricklecharge_bypass(struct device *dev,
+						struct device_attribute *attr,
+						const char *buf, size_t count)
+{
+	int reg, enable, error;
+
+	if (kstrtoint(buf, 0, &enable))
+		return -EINVAL;
+
+	error = bq32k_read(dev, &reg, BQ32K_CFG2, 1);
+	if (error)
+		return error;
+
+	if (enable) {
+		reg |= BQ32K_TCFE;
+		error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
+		if (error)
+			return error;
+
+		dev_info(dev, "Enabled trickle charge FET bypass.\n");
+	} else {
+		reg &= ~BQ32K_TCFE;
+		error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
+		if (error)
+			return error;
+
+		dev_info(dev, "Disabled trickle charge FET bypass.\n");
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR(trickle_charge_bypass, 0644,
+		   bq32k_sysfs_show_tricklecharge_bypass,
+		   bq32k_sysfs_store_tricklecharge_bypass);
+
+static int bq32k_sysfs_register(struct device *dev)
+{
+	return device_create_file(dev, &dev_attr_trickle_charge_bypass);
+}
+
+static void bq32k_sysfs_unregister(struct device *dev)
+{
+	device_remove_file(dev, &dev_attr_trickle_charge_bypass);
+}
+
+static int bq32k_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct rtc_device *rtc;
+	uint8_t reg;
+	int error;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	/* Check Oscillator Stop flag */
+	error = bq32k_read(dev, &reg, BQ32K_SECONDS, 1);
+	if (!error && (reg & BQ32K_STOP)) {
+		dev_warn(dev, "Oscillator was halted. Restarting...\n");
+		reg &= ~BQ32K_STOP;
+		error = bq32k_write(dev, &reg, BQ32K_SECONDS, 1);
+	}
+	if (error)
+		return error;
+
+	/* Check Oscillator Failure flag */
+	error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
+	if (error)
+		return error;
+	if (reg & BQ32K_OF)
+		dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
+
+	if (client->dev.of_node)
+		trickle_charger_of_init(dev, client->dev.of_node);
+
+	rtc = devm_rtc_device_register(&client->dev, bq32k_driver.driver.name,
+						&bq32k_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	error = bq32k_sysfs_register(&client->dev);
+	if (error) {
+		dev_err(&client->dev,
+			"Unable to create sysfs entries for rtc bq32000\n");
+		return error;
+	}
+
+
+	i2c_set_clientdata(client, rtc);
+
+	return 0;
+}
+
+static void bq32k_remove(struct i2c_client *client)
+{
+	bq32k_sysfs_unregister(&client->dev);
+}
+
+static const struct i2c_device_id bq32k_id[] = {
+	{ .name = "bq32000" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, bq32k_id);
+
+static const __maybe_unused struct of_device_id bq32k_of_match[] = {
+	{ .compatible = "ti,bq32000" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, bq32k_of_match);
+
+static struct i2c_driver bq32k_driver = {
+	.driver = {
+		.name	= "bq32k",
+		.of_match_table = of_match_ptr(bq32k_of_match),
+	},
+	.probe		= bq32k_probe,
+	.remove		= bq32k_remove,
+	.id_table	= bq32k_id,
+};
+
+module_i2c_driver(bq32k_driver);
+
+MODULE_AUTHOR("Semihalf, Piotr Ziecik <kosmo@semihalf.com>");
+MODULE_DESCRIPTION("TI BQ32000 I2C RTC driver");
+MODULE_LICENSE("GPL");