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, 278 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-xgene.c b/drivers/rtc/rtc-xgene.c
new file mode 100644
index 000000000..6660b664e
--- /dev/null
+++ b/drivers/rtc/rtc-xgene.c
@@ -0,0 +1,278 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * APM X-Gene SoC Real Time Clock Driver
+ *
+ * Copyright (c) 2014, Applied Micro Circuits Corporation
+ * Author: Rameshwar Prasad Sahu <rsahu@apm.com>
+ *         Loc Ho <lho@apm.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+/* RTC CSR Registers */
+#define RTC_CCVR		0x00
+#define RTC_CMR			0x04
+#define RTC_CLR			0x08
+#define RTC_CCR			0x0C
+#define  RTC_CCR_IE		BIT(0)
+#define  RTC_CCR_MASK		BIT(1)
+#define  RTC_CCR_EN		BIT(2)
+#define  RTC_CCR_WEN		BIT(3)
+#define RTC_STAT		0x10
+#define  RTC_STAT_BIT		BIT(0)
+#define RTC_RSTAT		0x14
+#define RTC_EOI			0x18
+#define RTC_VER			0x1C
+
+struct xgene_rtc_dev {
+	struct rtc_device *rtc;
+	void __iomem *csr_base;
+	struct clk *clk;
+	unsigned int irq_wake;
+	unsigned int irq_enabled;
+};
+
+static int xgene_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
+
+	rtc_time64_to_tm(readl(pdata->csr_base + RTC_CCVR), tm);
+	return 0;
+}
+
+static int xgene_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
+
+	/*
+	 * NOTE: After the following write, the RTC_CCVR is only reflected
+	 *       after the update cycle of 1 seconds.
+	 */
+	writel((u32)rtc_tm_to_time64(tm), pdata->csr_base + RTC_CLR);
+	readl(pdata->csr_base + RTC_CLR); /* Force a barrier */
+
+	return 0;
+}
+
+static int xgene_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
+
+	/* If possible, CMR should be read here */
+	rtc_time64_to_tm(0, &alrm->time);
+	alrm->enabled = readl(pdata->csr_base + RTC_CCR) & RTC_CCR_IE;
+
+	return 0;
+}
+
+static int xgene_rtc_alarm_irq_enable(struct device *dev, u32 enabled)
+{
+	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
+	u32 ccr;
+
+	ccr = readl(pdata->csr_base + RTC_CCR);
+	if (enabled) {
+		ccr &= ~RTC_CCR_MASK;
+		ccr |= RTC_CCR_IE;
+	} else {
+		ccr &= ~RTC_CCR_IE;
+		ccr |= RTC_CCR_MASK;
+	}
+	writel(ccr, pdata->csr_base + RTC_CCR);
+
+	return 0;
+}
+
+static int xgene_rtc_alarm_irq_enabled(struct device *dev)
+{
+	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
+
+	return readl(pdata->csr_base + RTC_CCR) & RTC_CCR_IE ? 1 : 0;
+}
+
+static int xgene_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
+
+	writel((u32)rtc_tm_to_time64(&alrm->time), pdata->csr_base + RTC_CMR);
+
+	xgene_rtc_alarm_irq_enable(dev, alrm->enabled);
+
+	return 0;
+}
+
+static const struct rtc_class_ops xgene_rtc_ops = {
+	.read_time	= xgene_rtc_read_time,
+	.set_time	= xgene_rtc_set_time,
+	.read_alarm	= xgene_rtc_read_alarm,
+	.set_alarm	= xgene_rtc_set_alarm,
+	.alarm_irq_enable = xgene_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t xgene_rtc_interrupt(int irq, void *id)
+{
+	struct xgene_rtc_dev *pdata = id;
+
+	/* Check if interrupt asserted */
+	if (!(readl(pdata->csr_base + RTC_STAT) & RTC_STAT_BIT))
+		return IRQ_NONE;
+
+	/* Clear interrupt */
+	readl(pdata->csr_base + RTC_EOI);
+
+	rtc_update_irq(pdata->rtc, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static int xgene_rtc_probe(struct platform_device *pdev)
+{
+	struct xgene_rtc_dev *pdata;
+	int ret;
+	int irq;
+
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, pdata);
+
+	pdata->csr_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pdata->csr_base))
+		return PTR_ERR(pdata->csr_base);
+
+	pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(pdata->rtc))
+		return PTR_ERR(pdata->rtc);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+	ret = devm_request_irq(&pdev->dev, irq, xgene_rtc_interrupt, 0,
+			       dev_name(&pdev->dev), pdata);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not request IRQ\n");
+		return ret;
+	}
+
+	pdata->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(pdata->clk)) {
+		dev_err(&pdev->dev, "Couldn't get the clock for RTC\n");
+		return -ENODEV;
+	}
+	ret = clk_prepare_enable(pdata->clk);
+	if (ret)
+		return ret;
+
+	/* Turn on the clock and the crystal */
+	writel(RTC_CCR_EN, pdata->csr_base + RTC_CCR);
+
+	ret = device_init_wakeup(&pdev->dev, true);
+	if (ret) {
+		clk_disable_unprepare(pdata->clk);
+		return ret;
+	}
+
+	pdata->rtc->ops = &xgene_rtc_ops;
+	pdata->rtc->range_max = U32_MAX;
+
+	ret = devm_rtc_register_device(pdata->rtc);
+	if (ret) {
+		clk_disable_unprepare(pdata->clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void xgene_rtc_remove(struct platform_device *pdev)
+{
+	struct xgene_rtc_dev *pdata = platform_get_drvdata(pdev);
+
+	xgene_rtc_alarm_irq_enable(&pdev->dev, 0);
+	device_init_wakeup(&pdev->dev, false);
+	clk_disable_unprepare(pdata->clk);
+}
+
+static int __maybe_unused xgene_rtc_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct xgene_rtc_dev *pdata = platform_get_drvdata(pdev);
+	int irq;
+
+	irq = platform_get_irq(pdev, 0);
+
+	/*
+	 * If this RTC alarm will be used for waking the system up,
+	 * don't disable it of course. Else we just disable the alarm
+	 * and await suspension.
+	 */
+	if (device_may_wakeup(&pdev->dev)) {
+		if (!enable_irq_wake(irq))
+			pdata->irq_wake = 1;
+	} else {
+		pdata->irq_enabled = xgene_rtc_alarm_irq_enabled(dev);
+		xgene_rtc_alarm_irq_enable(dev, 0);
+		clk_disable_unprepare(pdata->clk);
+	}
+	return 0;
+}
+
+static int __maybe_unused xgene_rtc_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct xgene_rtc_dev *pdata = platform_get_drvdata(pdev);
+	int irq;
+	int rc;
+
+	irq = platform_get_irq(pdev, 0);
+
+	if (device_may_wakeup(&pdev->dev)) {
+		if (pdata->irq_wake) {
+			disable_irq_wake(irq);
+			pdata->irq_wake = 0;
+		}
+	} else {
+		rc = clk_prepare_enable(pdata->clk);
+		if (rc) {
+			dev_err(dev, "Unable to enable clock error %d\n", rc);
+			return rc;
+		}
+		xgene_rtc_alarm_irq_enable(dev, pdata->irq_enabled);
+	}
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(xgene_rtc_pm_ops, xgene_rtc_suspend, xgene_rtc_resume);
+
+#ifdef CONFIG_OF
+static const struct of_device_id xgene_rtc_of_match[] = {
+	{.compatible = "apm,xgene-rtc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, xgene_rtc_of_match);
+#endif
+
+static struct platform_driver xgene_rtc_driver = {
+	.probe		= xgene_rtc_probe,
+	.remove		= xgene_rtc_remove,
+	.driver		= {
+		.name	= "xgene-rtc",
+		.pm = &xgene_rtc_pm_ops,
+		.of_match_table	= of_match_ptr(xgene_rtc_of_match),
+	},
+};
+
+module_platform_driver(xgene_rtc_driver);
+
+MODULE_DESCRIPTION("APM X-Gene SoC RTC driver");
+MODULE_AUTHOR("Rameshwar Sahu <rsahu@apm.com>");
+MODULE_LICENSE("GPL");