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, 155 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-gx6605s.c b/drivers/clocksource/timer-gx6605s.c
new file mode 100644
index 000000000..8d386adbe
--- /dev/null
+++ b/drivers/clocksource/timer-gx6605s.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/sched_clock.h>
+
+#include "timer-of.h"
+
+#define CLKSRC_OFFSET	0x40
+
+#define TIMER_STATUS	0x00
+#define TIMER_VALUE	0x04
+#define TIMER_CONTRL	0x10
+#define TIMER_CONFIG	0x20
+#define TIMER_DIV	0x24
+#define TIMER_INI	0x28
+
+#define GX6605S_STATUS_CLR	BIT(0)
+#define GX6605S_CONTRL_RST	BIT(0)
+#define GX6605S_CONTRL_START	BIT(1)
+#define GX6605S_CONFIG_EN	BIT(0)
+#define GX6605S_CONFIG_IRQ_EN	BIT(1)
+
+static irqreturn_t gx6605s_timer_interrupt(int irq, void *dev)
+{
+	struct clock_event_device *ce = dev;
+	void __iomem *base = timer_of_base(to_timer_of(ce));
+
+	writel_relaxed(GX6605S_STATUS_CLR, base + TIMER_STATUS);
+	writel_relaxed(0, base + TIMER_INI);
+
+	ce->event_handler(ce);
+
+	return IRQ_HANDLED;
+}
+
+static int gx6605s_timer_set_oneshot(struct clock_event_device *ce)
+{
+	void __iomem *base = timer_of_base(to_timer_of(ce));
+
+	/* reset and stop counter */
+	writel_relaxed(GX6605S_CONTRL_RST, base + TIMER_CONTRL);
+
+	/* enable with irq and start */
+	writel_relaxed(GX6605S_CONFIG_EN | GX6605S_CONFIG_IRQ_EN,
+		       base + TIMER_CONFIG);
+
+	return 0;
+}
+
+static int gx6605s_timer_set_next_event(unsigned long delta,
+					struct clock_event_device *ce)
+{
+	void __iomem *base = timer_of_base(to_timer_of(ce));
+
+	/* use reset to pause timer */
+	writel_relaxed(GX6605S_CONTRL_RST, base + TIMER_CONTRL);
+
+	/* config next timeout value */
+	writel_relaxed(ULONG_MAX - delta, base + TIMER_INI);
+	writel_relaxed(GX6605S_CONTRL_START, base + TIMER_CONTRL);
+
+	return 0;
+}
+
+static int gx6605s_timer_shutdown(struct clock_event_device *ce)
+{
+	void __iomem *base = timer_of_base(to_timer_of(ce));
+
+	writel_relaxed(0, base + TIMER_CONTRL);
+	writel_relaxed(0, base + TIMER_CONFIG);
+
+	return 0;
+}
+
+static struct timer_of to = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_BASE | TIMER_OF_CLOCK,
+	.clkevt = {
+		.rating			= 300,
+		.features		= CLOCK_EVT_FEAT_DYNIRQ |
+					  CLOCK_EVT_FEAT_ONESHOT,
+		.set_state_shutdown	= gx6605s_timer_shutdown,
+		.set_state_oneshot	= gx6605s_timer_set_oneshot,
+		.set_next_event		= gx6605s_timer_set_next_event,
+		.cpumask		= cpu_possible_mask,
+	},
+	.of_irq = {
+		.handler		= gx6605s_timer_interrupt,
+		.flags			= IRQF_TIMER | IRQF_IRQPOLL,
+	},
+};
+
+static u64 notrace gx6605s_sched_clock_read(void)
+{
+	void __iomem *base;
+
+	base = timer_of_base(&to) + CLKSRC_OFFSET;
+
+	return (u64)readl_relaxed(base + TIMER_VALUE);
+}
+
+static void gx6605s_clkevt_init(void __iomem *base)
+{
+	writel_relaxed(0, base + TIMER_DIV);
+	writel_relaxed(0, base + TIMER_CONFIG);
+
+	clockevents_config_and_register(&to.clkevt, timer_of_rate(&to), 2,
+					ULONG_MAX);
+}
+
+static int gx6605s_clksrc_init(void __iomem *base)
+{
+	writel_relaxed(0, base + TIMER_DIV);
+	writel_relaxed(0, base + TIMER_INI);
+
+	writel_relaxed(GX6605S_CONTRL_RST, base + TIMER_CONTRL);
+
+	writel_relaxed(GX6605S_CONFIG_EN, base + TIMER_CONFIG);
+
+	writel_relaxed(GX6605S_CONTRL_START, base + TIMER_CONTRL);
+
+	sched_clock_register(gx6605s_sched_clock_read, 32, timer_of_rate(&to));
+
+	return clocksource_mmio_init(base + TIMER_VALUE, "gx6605s",
+			timer_of_rate(&to), 200, 32, clocksource_mmio_readl_up);
+}
+
+static int __init gx6605s_timer_init(struct device_node *np)
+{
+	int ret;
+
+	/*
+	 * The timer driver is for nationalchip gx6605s SOC and there are two
+	 * same timer in gx6605s. We use one for clkevt and another for clksrc.
+	 *
+	 * The timer is mmio map to access, so we need give mmio address in dts.
+	 *
+	 * It provides a 32bit countup timer and interrupt will be caused by
+	 * count-overflow.
+	 * So we need set-next-event by ULONG_MAX - delta in TIMER_INI reg.
+	 *
+	 * The counter at 0x0  offset is clock event.
+	 * The counter at 0x40 offset is clock source.
+	 * They are the same in hardware, just different used by driver.
+	 */
+	ret = timer_of_init(np, &to);
+	if (ret)
+		return ret;
+
+	gx6605s_clkevt_init(timer_of_base(&to));
+
+	return gx6605s_clksrc_init(timer_of_base(&to) + CLKSRC_OFFSET);
+}
+TIMER_OF_DECLARE(csky_gx6605s_timer, "csky,gx6605s-timer", gx6605s_timer_init);