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, 220 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-max8907.c b/drivers/rtc/rtc-max8907.c
new file mode 100644
index 000000000..af97140dd
--- /dev/null
+++ b/drivers/rtc/rtc-max8907.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * RTC driver for Maxim MAX8907
+ *
+ * Copyright (c) 2011-2012, NVIDIA Corporation.
+ *
+ * Based on drivers/rtc/rtc-max8925.c,
+ * Copyright (C) 2009-2010 Marvell International Ltd.
+ */
+
+#include <linux/bcd.h>
+#include <linux/mfd/max8907.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+enum {
+	RTC_SEC = 0,
+	RTC_MIN,
+	RTC_HOUR,
+	RTC_WEEKDAY,
+	RTC_DATE,
+	RTC_MONTH,
+	RTC_YEAR1,
+	RTC_YEAR2,
+};
+
+#define TIME_NUM			8
+#define ALARM_1SEC			(1 << 7)
+#define HOUR_12				(1 << 7)
+#define HOUR_AM_PM			(1 << 5)
+#define ALARM0_IRQ			(1 << 3)
+#define ALARM1_IRQ			(1 << 2)
+#define ALARM0_STATUS			(1 << 2)
+#define ALARM1_STATUS			(1 << 1)
+
+struct max8907_rtc {
+	struct max8907		*max8907;
+	struct regmap		*regmap;
+	struct rtc_device	*rtc_dev;
+	int			irq;
+};
+
+static irqreturn_t max8907_irq_handler(int irq, void *data)
+{
+	struct max8907_rtc *rtc = data;
+
+	regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0);
+
+	rtc_update_irq(rtc->rtc_dev, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static void regs_to_tm(u8 *regs, struct rtc_time *tm)
+{
+	tm->tm_year = bcd2bin(regs[RTC_YEAR2]) * 100 +
+		bcd2bin(regs[RTC_YEAR1]) - 1900;
+	tm->tm_mon = bcd2bin(regs[RTC_MONTH] & 0x1f) - 1;
+	tm->tm_mday = bcd2bin(regs[RTC_DATE] & 0x3f);
+	tm->tm_wday = (regs[RTC_WEEKDAY] & 0x07);
+	if (regs[RTC_HOUR] & HOUR_12) {
+		tm->tm_hour = bcd2bin(regs[RTC_HOUR] & 0x01f);
+		if (tm->tm_hour == 12)
+			tm->tm_hour = 0;
+		if (regs[RTC_HOUR] & HOUR_AM_PM)
+			tm->tm_hour += 12;
+	} else {
+		tm->tm_hour = bcd2bin(regs[RTC_HOUR] & 0x03f);
+	}
+	tm->tm_min = bcd2bin(regs[RTC_MIN] & 0x7f);
+	tm->tm_sec = bcd2bin(regs[RTC_SEC] & 0x7f);
+}
+
+static void tm_to_regs(struct rtc_time *tm, u8 *regs)
+{
+	u8 high, low;
+
+	high = (tm->tm_year + 1900) / 100;
+	low = tm->tm_year % 100;
+	regs[RTC_YEAR2] = bin2bcd(high);
+	regs[RTC_YEAR1] = bin2bcd(low);
+	regs[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
+	regs[RTC_DATE] = bin2bcd(tm->tm_mday);
+	regs[RTC_WEEKDAY] = tm->tm_wday;
+	regs[RTC_HOUR] = bin2bcd(tm->tm_hour);
+	regs[RTC_MIN] = bin2bcd(tm->tm_min);
+	regs[RTC_SEC] = bin2bcd(tm->tm_sec);
+}
+
+static int max8907_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+	int ret;
+
+	ret = regmap_bulk_read(rtc->regmap, MAX8907_REG_RTC_SEC, regs,
+			       TIME_NUM);
+	if (ret < 0)
+		return ret;
+
+	regs_to_tm(regs, tm);
+
+	return 0;
+}
+
+static int max8907_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+
+	tm_to_regs(tm, regs);
+
+	return regmap_bulk_write(rtc->regmap, MAX8907_REG_RTC_SEC, regs,
+				 TIME_NUM);
+}
+
+static int max8907_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+	unsigned int val;
+	int ret;
+
+	ret = regmap_bulk_read(rtc->regmap, MAX8907_REG_ALARM0_SEC, regs,
+			       TIME_NUM);
+	if (ret < 0)
+		return ret;
+
+	regs_to_tm(regs, &alrm->time);
+
+	ret = regmap_read(rtc->regmap, MAX8907_REG_ALARM0_CNTL, &val);
+	if (ret < 0)
+		return ret;
+
+	alrm->enabled = !!(val & 0x7f);
+
+	return 0;
+}
+
+static int max8907_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+	int ret;
+
+	tm_to_regs(&alrm->time, regs);
+
+	/* Disable alarm while we update the target time */
+	ret = regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_bulk_write(rtc->regmap, MAX8907_REG_ALARM0_SEC, regs,
+				TIME_NUM);
+	if (ret < 0)
+		return ret;
+
+	if (alrm->enabled)
+		ret = regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0x77);
+
+	return ret;
+}
+
+static const struct rtc_class_ops max8907_rtc_ops = {
+	.read_time	= max8907_rtc_read_time,
+	.set_time	= max8907_rtc_set_time,
+	.read_alarm	= max8907_rtc_read_alarm,
+	.set_alarm	= max8907_rtc_set_alarm,
+};
+
+static int max8907_rtc_probe(struct platform_device *pdev)
+{
+	struct max8907 *max8907 = dev_get_drvdata(pdev->dev.parent);
+	struct max8907_rtc *rtc;
+	int ret;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, rtc);
+
+	rtc->max8907 = max8907;
+	rtc->regmap = max8907->regmap_rtc;
+
+	rtc->rtc_dev = devm_rtc_device_register(&pdev->dev, "max8907-rtc",
+					&max8907_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc->rtc_dev)) {
+		ret = PTR_ERR(rtc->rtc_dev);
+		dev_err(&pdev->dev, "Failed to register RTC device: %d\n", ret);
+		return ret;
+	}
+
+	rtc->irq = regmap_irq_get_virq(max8907->irqc_rtc,
+				       MAX8907_IRQ_RTC_ALARM0);
+	if (rtc->irq < 0)
+		return rtc->irq;
+
+	ret = devm_request_threaded_irq(&pdev->dev, rtc->irq, NULL,
+				max8907_irq_handler,
+				IRQF_ONESHOT, "max8907-alarm0", rtc);
+	if (ret < 0)
+		dev_err(&pdev->dev, "Failed to request IRQ%d: %d\n",
+			rtc->irq, ret);
+
+	return ret;
+}
+
+static struct platform_driver max8907_rtc_driver = {
+	.driver = {
+		.name = "max8907-rtc",
+	},
+	.probe = max8907_rtc_probe,
+};
+module_platform_driver(max8907_rtc_driver);
+
+MODULE_DESCRIPTION("Maxim MAX8907 RTC driver");
+MODULE_LICENSE("GPL v2");