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, 157 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-ralink.c b/drivers/clocksource/timer-ralink.c
new file mode 100644
index 000000000..68434d9ed
--- /dev/null
+++ b/drivers/clocksource/timer-ralink.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ralink System Tick Counter driver present on RT3352 and MT7620 SoCs.
+ *
+ * Copyright (C) 2013 by John Crispin <john@phrozen.org>
+ */
+
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/interrupt.h>
+#include <linux/reset.h>
+#include <linux/init.h>
+#include <linux/time.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+
+#define SYSTICK_FREQ		(50 * 1000)
+
+#define SYSTICK_CONFIG		0x00
+#define SYSTICK_COMPARE		0x04
+#define SYSTICK_COUNT		0x08
+
+/* route systick irq to mips irq 7 instead of the r4k-timer */
+#define CFG_EXT_STK_EN		0x2
+/* enable the counter */
+#define CFG_CNT_EN		0x1
+
+struct systick_device {
+	void __iomem *membase;
+	struct clock_event_device dev;
+	int irq_requested;
+	int freq_scale;
+};
+
+static int systick_set_oneshot(struct clock_event_device *evt);
+static int systick_shutdown(struct clock_event_device *evt);
+
+static int systick_next_event(unsigned long delta,
+			      struct clock_event_device *evt)
+{
+	struct systick_device *sdev;
+	u32 count;
+
+	sdev = container_of(evt, struct systick_device, dev);
+	count = ioread32(sdev->membase + SYSTICK_COUNT);
+	count = (count + delta) % SYSTICK_FREQ;
+	iowrite32(count, sdev->membase + SYSTICK_COMPARE);
+
+	return 0;
+}
+
+static void systick_event_handler(struct clock_event_device *dev)
+{
+	/* noting to do here */
+}
+
+static irqreturn_t systick_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *dev = (struct clock_event_device *)dev_id;
+
+	dev->event_handler(dev);
+
+	return IRQ_HANDLED;
+}
+
+static struct systick_device systick = {
+	.dev = {
+		/*
+		 * cevt-r4k uses 300, make sure systick
+		 * gets used if available
+		 */
+		.rating			= 310,
+		.features		= CLOCK_EVT_FEAT_ONESHOT,
+		.set_next_event		= systick_next_event,
+		.set_state_shutdown	= systick_shutdown,
+		.set_state_oneshot	= systick_set_oneshot,
+		.event_handler		= systick_event_handler,
+	},
+};
+
+static int systick_shutdown(struct clock_event_device *evt)
+{
+	struct systick_device *sdev;
+
+	sdev = container_of(evt, struct systick_device, dev);
+
+	if (sdev->irq_requested)
+		free_irq(systick.dev.irq, &systick.dev);
+	sdev->irq_requested = 0;
+	iowrite32(0, systick.membase + SYSTICK_CONFIG);
+
+	return 0;
+}
+
+static int systick_set_oneshot(struct clock_event_device *evt)
+{
+	const char *name = systick.dev.name;
+	struct systick_device *sdev;
+	int irq = systick.dev.irq;
+
+	sdev = container_of(evt, struct systick_device, dev);
+
+	if (!sdev->irq_requested) {
+		if (request_irq(irq, systick_interrupt,
+				IRQF_PERCPU | IRQF_TIMER, name, &systick.dev))
+			pr_err("Failed to request irq %d (%s)\n", irq, name);
+	}
+	sdev->irq_requested = 1;
+	iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
+		  systick.membase + SYSTICK_CONFIG);
+
+	return 0;
+}
+
+static int __init ralink_systick_init(struct device_node *np)
+{
+	int ret;
+
+	systick.membase = of_iomap(np, 0);
+	if (!systick.membase)
+		return -ENXIO;
+
+	systick.dev.name = np->name;
+	clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60);
+	systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev);
+	systick.dev.max_delta_ticks = 0x7fff;
+	systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
+	systick.dev.min_delta_ticks = 0x3;
+	systick.dev.irq = irq_of_parse_and_map(np, 0);
+	if (!systick.dev.irq) {
+		pr_err("%pOFn: request_irq failed", np);
+		ret = -EINVAL;
+		goto err_iounmap;
+	}
+
+	ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
+				    SYSTICK_FREQ, 301, 16,
+				    clocksource_mmio_readl_up);
+	if (ret)
+		goto err_free_irq;
+
+	clockevents_register_device(&systick.dev);
+
+	pr_info("%pOFn: running - mult: %d, shift: %d\n",
+			np, systick.dev.mult, systick.dev.shift);
+
+	return 0;
+
+err_free_irq:
+	irq_dispose_mapping(systick.dev.irq);
+err_iounmap:
+	iounmap(systick.membase);
+	return ret;
+}
+
+TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);