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, 165 insertions, 0 deletions

diff --git a/drivers/extcon/extcon-gpio.c b/drivers/extcon/extcon-gpio.c
new file mode 100644
index 000000000..4105df74f
--- /dev/null
+++ b/drivers/extcon/extcon-gpio.c
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * extcon_gpio.c - Single-state GPIO extcon driver based on extcon class
+ *
+ * Copyright (C) 2008 Google, Inc.
+ * Author: Mike Lockwood <lockwood@android.com>
+ *
+ * Modified by MyungJoo Ham <myungjoo.ham@samsung.com> to support extcon
+ * (originally switch class is supported)
+ */
+
+#include <linux/devm-helpers.h>
+#include <linux/extcon-provider.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+/**
+ * struct gpio_extcon_data - A simple GPIO-controlled extcon device state container.
+ * @edev:		Extcon device.
+ * @work:		Work fired by the interrupt.
+ * @debounce_jiffies:	Number of jiffies to wait for the GPIO to stabilize, from the debounce
+ *			value.
+ * @gpiod:		GPIO descriptor for this external connector.
+ * @extcon_id:		The unique id of specific external connector.
+ * @debounce:		Debounce time for GPIO IRQ in ms.
+ * @check_on_resume:	Boolean describing whether to check the state of gpio
+ *			while resuming from sleep.
+ */
+struct gpio_extcon_data {
+	struct extcon_dev *edev;
+	struct delayed_work work;
+	unsigned long debounce_jiffies;
+	struct gpio_desc *gpiod;
+	unsigned int extcon_id;
+	unsigned long debounce;
+	bool check_on_resume;
+};
+
+static void gpio_extcon_work(struct work_struct *work)
+{
+	int state;
+	struct gpio_extcon_data	*data =
+		container_of(to_delayed_work(work), struct gpio_extcon_data,
+			     work);
+
+	state = gpiod_get_value_cansleep(data->gpiod);
+	extcon_set_state_sync(data->edev, data->extcon_id, state);
+}
+
+static irqreturn_t gpio_irq_handler(int irq, void *dev_id)
+{
+	struct gpio_extcon_data *data = dev_id;
+
+	queue_delayed_work(system_power_efficient_wq, &data->work,
+			      data->debounce_jiffies);
+	return IRQ_HANDLED;
+}
+
+static int gpio_extcon_probe(struct platform_device *pdev)
+{
+	struct gpio_extcon_data *data;
+	struct device *dev = &pdev->dev;
+	unsigned long irq_flags;
+	int irq;
+	int ret;
+
+	data = devm_kzalloc(dev, sizeof(struct gpio_extcon_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/*
+	 * FIXME: extcon_id represents the unique identifier of external
+	 * connectors such as EXTCON_USB, EXTCON_DISP_HDMI and so on. extcon_id
+	 * is necessary to register the extcon device. But, it's not yet
+	 * developed to get the extcon id from device-tree or others.
+	 * On later, it have to be solved.
+	 */
+	if (data->extcon_id > EXTCON_NONE)
+		return -EINVAL;
+
+	data->gpiod = devm_gpiod_get(dev, "extcon", GPIOD_IN);
+	if (IS_ERR(data->gpiod))
+		return PTR_ERR(data->gpiod);
+	irq = gpiod_to_irq(data->gpiod);
+	if (irq <= 0)
+		return irq;
+
+	/*
+	 * It is unlikely that this is an acknowledged interrupt that goes
+	 * away after handling, what we are looking for are falling edges
+	 * if the signal is active low, and rising edges if the signal is
+	 * active high.
+	 */
+	if (gpiod_is_active_low(data->gpiod))
+		irq_flags = IRQF_TRIGGER_FALLING;
+	else
+		irq_flags = IRQF_TRIGGER_RISING;
+
+	/* Allocate the memory of extcon devie and register extcon device */
+	data->edev = devm_extcon_dev_allocate(dev, &data->extcon_id);
+	if (IS_ERR(data->edev)) {
+		dev_err(dev, "failed to allocate extcon device\n");
+		return -ENOMEM;
+	}
+
+	ret = devm_extcon_dev_register(dev, data->edev);
+	if (ret < 0)
+		return ret;
+
+	ret = devm_delayed_work_autocancel(dev, &data->work, gpio_extcon_work);
+	if (ret)
+		return ret;
+
+	/*
+	 * Request the interrupt of gpio to detect whether external connector
+	 * is attached or detached.
+	 */
+	ret = devm_request_any_context_irq(dev, irq,
+					gpio_irq_handler, irq_flags,
+					pdev->name, data);
+	if (ret < 0)
+		return ret;
+
+	platform_set_drvdata(pdev, data);
+	/* Perform initial detection */
+	gpio_extcon_work(&data->work.work);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int gpio_extcon_resume(struct device *dev)
+{
+	struct gpio_extcon_data *data;
+
+	data = dev_get_drvdata(dev);
+	if (data->check_on_resume)
+		queue_delayed_work(system_power_efficient_wq,
+			&data->work, data->debounce_jiffies);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(gpio_extcon_pm_ops, NULL, gpio_extcon_resume);
+
+static struct platform_driver gpio_extcon_driver = {
+	.probe		= gpio_extcon_probe,
+	.driver		= {
+		.name	= "extcon-gpio",
+		.pm	= &gpio_extcon_pm_ops,
+	},
+};
+
+module_platform_driver(gpio_extcon_driver);
+
+MODULE_AUTHOR("Mike Lockwood <lockwood@android.com>");
+MODULE_DESCRIPTION("GPIO extcon driver");
+MODULE_LICENSE("GPL");