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, 207 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-goldfish.c b/drivers/rtc/rtc-goldfish.c
new file mode 100644
index 000000000..53ec7173c
--- /dev/null
+++ b/drivers/rtc/rtc-goldfish.c
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0
+/* drivers/rtc/rtc-goldfish.c
+ *
+ * Copyright (C) 2007 Google, Inc.
+ * Copyright (C) 2017 Imagination Technologies Ltd.
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/goldfish.h>
+#include <clocksource/timer-goldfish.h>
+
+struct goldfish_rtc {
+	void __iomem *base;
+	int irq;
+	struct rtc_device *rtc;
+};
+
+static int goldfish_rtc_read_alarm(struct device *dev,
+				   struct rtc_wkalrm *alrm)
+{
+	u64 rtc_alarm;
+	u64 rtc_alarm_low;
+	u64 rtc_alarm_high;
+	void __iomem *base;
+	struct goldfish_rtc *rtcdrv;
+
+	rtcdrv = dev_get_drvdata(dev);
+	base = rtcdrv->base;
+
+	rtc_alarm_low = gf_ioread32(base + TIMER_ALARM_LOW);
+	rtc_alarm_high = gf_ioread32(base + TIMER_ALARM_HIGH);
+	rtc_alarm = (rtc_alarm_high << 32) | rtc_alarm_low;
+
+	do_div(rtc_alarm, NSEC_PER_SEC);
+	memset(alrm, 0, sizeof(struct rtc_wkalrm));
+
+	rtc_time64_to_tm(rtc_alarm, &alrm->time);
+
+	if (gf_ioread32(base + TIMER_ALARM_STATUS))
+		alrm->enabled = 1;
+	else
+		alrm->enabled = 0;
+
+	return 0;
+}
+
+static int goldfish_rtc_set_alarm(struct device *dev,
+				  struct rtc_wkalrm *alrm)
+{
+	struct goldfish_rtc *rtcdrv;
+	u64 rtc_alarm64;
+	u64 rtc_status_reg;
+	void __iomem *base;
+
+	rtcdrv = dev_get_drvdata(dev);
+	base = rtcdrv->base;
+
+	if (alrm->enabled) {
+		rtc_alarm64 = rtc_tm_to_time64(&alrm->time) * NSEC_PER_SEC;
+		gf_iowrite32((rtc_alarm64 >> 32), base + TIMER_ALARM_HIGH);
+		gf_iowrite32(rtc_alarm64, base + TIMER_ALARM_LOW);
+		gf_iowrite32(1, base + TIMER_IRQ_ENABLED);
+	} else {
+		/*
+		 * if this function was called with enabled=0
+		 * then it could mean that the application is
+		 * trying to cancel an ongoing alarm
+		 */
+		rtc_status_reg = gf_ioread32(base + TIMER_ALARM_STATUS);
+		if (rtc_status_reg)
+			gf_iowrite32(1, base + TIMER_CLEAR_ALARM);
+	}
+
+	return 0;
+}
+
+static int goldfish_rtc_alarm_irq_enable(struct device *dev,
+					 unsigned int enabled)
+{
+	void __iomem *base;
+	struct goldfish_rtc *rtcdrv;
+
+	rtcdrv = dev_get_drvdata(dev);
+	base = rtcdrv->base;
+
+	if (enabled)
+		gf_iowrite32(1, base + TIMER_IRQ_ENABLED);
+	else
+		gf_iowrite32(0, base + TIMER_IRQ_ENABLED);
+
+	return 0;
+}
+
+static irqreturn_t goldfish_rtc_interrupt(int irq, void *dev_id)
+{
+	struct goldfish_rtc *rtcdrv = dev_id;
+	void __iomem *base = rtcdrv->base;
+
+	gf_iowrite32(1, base + TIMER_CLEAR_INTERRUPT);
+
+	rtc_update_irq(rtcdrv->rtc, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static int goldfish_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct goldfish_rtc *rtcdrv;
+	void __iomem *base;
+	u64 time_high;
+	u64 time_low;
+	u64 time;
+
+	rtcdrv = dev_get_drvdata(dev);
+	base = rtcdrv->base;
+
+	time_low = gf_ioread32(base + TIMER_TIME_LOW);
+	time_high = gf_ioread32(base + TIMER_TIME_HIGH);
+	time = (time_high << 32) | time_low;
+
+	do_div(time, NSEC_PER_SEC);
+
+	rtc_time64_to_tm(time, tm);
+
+	return 0;
+}
+
+static int goldfish_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct goldfish_rtc *rtcdrv;
+	void __iomem *base;
+	u64 now64;
+
+	rtcdrv = dev_get_drvdata(dev);
+	base = rtcdrv->base;
+
+	now64 = rtc_tm_to_time64(tm) * NSEC_PER_SEC;
+	gf_iowrite32((now64 >> 32), base + TIMER_TIME_HIGH);
+	gf_iowrite32(now64, base + TIMER_TIME_LOW);
+
+	return 0;
+}
+
+static const struct rtc_class_ops goldfish_rtc_ops = {
+	.read_time	= goldfish_rtc_read_time,
+	.set_time	= goldfish_rtc_set_time,
+	.read_alarm	= goldfish_rtc_read_alarm,
+	.set_alarm	= goldfish_rtc_set_alarm,
+	.alarm_irq_enable = goldfish_rtc_alarm_irq_enable
+};
+
+static int goldfish_rtc_probe(struct platform_device *pdev)
+{
+	struct goldfish_rtc *rtcdrv;
+	int err;
+
+	rtcdrv = devm_kzalloc(&pdev->dev, sizeof(*rtcdrv), GFP_KERNEL);
+	if (!rtcdrv)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, rtcdrv);
+	rtcdrv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(rtcdrv->base))
+		return PTR_ERR(rtcdrv->base);
+
+	rtcdrv->irq = platform_get_irq(pdev, 0);
+	if (rtcdrv->irq < 0)
+		return -ENODEV;
+
+	rtcdrv->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtcdrv->rtc))
+		return PTR_ERR(rtcdrv->rtc);
+
+	rtcdrv->rtc->ops = &goldfish_rtc_ops;
+	rtcdrv->rtc->range_max = U64_MAX / NSEC_PER_SEC;
+
+	err = devm_request_irq(&pdev->dev, rtcdrv->irq,
+			       goldfish_rtc_interrupt,
+			       0, pdev->name, rtcdrv);
+	if (err)
+		return err;
+
+	return devm_rtc_register_device(rtcdrv->rtc);
+}
+
+static const struct of_device_id goldfish_rtc_of_match[] = {
+	{ .compatible = "google,goldfish-rtc", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, goldfish_rtc_of_match);
+
+static struct platform_driver goldfish_rtc = {
+	.probe = goldfish_rtc_probe,
+	.driver = {
+		.name = "goldfish_rtc",
+		.of_match_table = goldfish_rtc_of_match,
+	}
+};
+
+module_platform_driver(goldfish_rtc);
+
+MODULE_DESCRIPTION("Android Goldfish Real Time Clock driver");
+MODULE_LICENSE("GPL v2");