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, 134 insertions, 0 deletions

diff --git a/drivers/input/misc/pcspkr.c b/drivers/input/misc/pcspkr.c
new file mode 100644
index 000000000..046780840
--- /dev/null
+++ b/drivers/input/misc/pcspkr.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  PC Speaker beeper driver for Linux
+ *
+ *  Copyright (c) 2002 Vojtech Pavlik
+ *  Copyright (c) 1992 Orest Zborowski
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i8253.h>
+#include <linux/input.h>
+#include <linux/platform_device.h>
+#include <linux/timex.h>
+#include <linux/io.h>
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION("PC Speaker beeper driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:pcspkr");
+
+static int pcspkr_event(struct input_dev *dev, unsigned int type,
+			unsigned int code, int value)
+{
+	unsigned int count = 0;
+	unsigned long flags;
+
+	if (type != EV_SND)
+		return -EINVAL;
+
+	switch (code) {
+	case SND_BELL:
+		if (value)
+			value = 1000;
+		break;
+	case SND_TONE:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (value > 20 && value < 32767)
+		count = PIT_TICK_RATE / value;
+
+	raw_spin_lock_irqsave(&i8253_lock, flags);
+
+	if (count) {
+		/* set command for counter 2, 2 byte write */
+		outb_p(0xB6, 0x43);
+		/* select desired HZ */
+		outb_p(count & 0xff, 0x42);
+		outb((count >> 8) & 0xff, 0x42);
+		/* enable counter 2 */
+		outb_p(inb_p(0x61) | 3, 0x61);
+	} else {
+		/* disable counter 2 */
+		outb(inb_p(0x61) & 0xFC, 0x61);
+	}
+
+	raw_spin_unlock_irqrestore(&i8253_lock, flags);
+
+	return 0;
+}
+
+static int pcspkr_probe(struct platform_device *dev)
+{
+	struct input_dev *pcspkr_dev;
+	int err;
+
+	pcspkr_dev = input_allocate_device();
+	if (!pcspkr_dev)
+		return -ENOMEM;
+
+	pcspkr_dev->name = "PC Speaker";
+	pcspkr_dev->phys = "isa0061/input0";
+	pcspkr_dev->id.bustype = BUS_ISA;
+	pcspkr_dev->id.vendor = 0x001f;
+	pcspkr_dev->id.product = 0x0001;
+	pcspkr_dev->id.version = 0x0100;
+	pcspkr_dev->dev.parent = &dev->dev;
+
+	pcspkr_dev->evbit[0] = BIT_MASK(EV_SND);
+	pcspkr_dev->sndbit[0] = BIT_MASK(SND_BELL) | BIT_MASK(SND_TONE);
+	pcspkr_dev->event = pcspkr_event;
+
+	err = input_register_device(pcspkr_dev);
+	if (err) {
+		input_free_device(pcspkr_dev);
+		return err;
+	}
+
+	platform_set_drvdata(dev, pcspkr_dev);
+
+	return 0;
+}
+
+static void pcspkr_remove(struct platform_device *dev)
+{
+	struct input_dev *pcspkr_dev = platform_get_drvdata(dev);
+
+	input_unregister_device(pcspkr_dev);
+	/* turn off the speaker */
+	pcspkr_event(NULL, EV_SND, SND_BELL, 0);
+}
+
+static int pcspkr_suspend(struct device *dev)
+{
+	pcspkr_event(NULL, EV_SND, SND_BELL, 0);
+
+	return 0;
+}
+
+static void pcspkr_shutdown(struct platform_device *dev)
+{
+	/* turn off the speaker */
+	pcspkr_event(NULL, EV_SND, SND_BELL, 0);
+}
+
+static const struct dev_pm_ops pcspkr_pm_ops = {
+	.suspend = pcspkr_suspend,
+};
+
+static struct platform_driver pcspkr_platform_driver = {
+	.driver		= {
+		.name	= "pcspkr",
+		.pm	= &pcspkr_pm_ops,
+	},
+	.probe		= pcspkr_probe,
+	.remove		= pcspkr_remove,
+	.shutdown	= pcspkr_shutdown,
+};
+module_platform_driver(pcspkr_platform_driver);
+