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, 202 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-rda.c b/drivers/clocksource/timer-rda.c
new file mode 100644
index 000000000..0be8e0597
--- /dev/null
+++ b/drivers/clocksource/timer-rda.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * RDA8810PL SoC timer driver
+ *
+ * Copyright RDA Microelectronics Company Limited
+ * Copyright (c) 2017 Andreas Färber
+ * Copyright (c) 2018 Manivannan Sadhasivam
+ *
+ * RDA8810PL has two independent timers: OSTIMER (56 bit) and HWTIMER (64 bit).
+ * Each timer provides optional interrupt support. In this driver, OSTIMER is
+ * used for clockevents and HWTIMER is used for clocksource.
+ */
+
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/sched_clock.h>
+
+#include "timer-of.h"
+
+#define RDA_OSTIMER_LOADVAL_L	0x000
+#define RDA_OSTIMER_CTRL	0x004
+#define RDA_HWTIMER_LOCKVAL_L	0x024
+#define RDA_HWTIMER_LOCKVAL_H	0x028
+#define RDA_TIMER_IRQ_MASK_SET	0x02c
+#define RDA_TIMER_IRQ_MASK_CLR	0x030
+#define RDA_TIMER_IRQ_CLR	0x034
+
+#define RDA_OSTIMER_CTRL_ENABLE		BIT(24)
+#define RDA_OSTIMER_CTRL_REPEAT		BIT(28)
+#define RDA_OSTIMER_CTRL_LOAD		BIT(30)
+
+#define RDA_TIMER_IRQ_MASK_OSTIMER	BIT(0)
+
+#define RDA_TIMER_IRQ_CLR_OSTIMER	BIT(0)
+
+static int rda_ostimer_start(void __iomem *base, bool periodic, u64 cycles)
+{
+	u32 ctrl, load_l;
+
+	load_l = (u32)cycles;
+	ctrl = ((cycles >> 32) & 0xffffff);
+	ctrl |= RDA_OSTIMER_CTRL_LOAD | RDA_OSTIMER_CTRL_ENABLE;
+	if (periodic)
+		ctrl |= RDA_OSTIMER_CTRL_REPEAT;
+
+	/* Enable ostimer interrupt first */
+	writel_relaxed(RDA_TIMER_IRQ_MASK_OSTIMER,
+		       base + RDA_TIMER_IRQ_MASK_SET);
+
+	/* Write low 32 bits first, high 24 bits are with ctrl */
+	writel_relaxed(load_l, base + RDA_OSTIMER_LOADVAL_L);
+	writel_relaxed(ctrl, base + RDA_OSTIMER_CTRL);
+
+	return 0;
+}
+
+static int rda_ostimer_stop(void __iomem *base)
+{
+	/* Disable ostimer interrupt first */
+	writel_relaxed(RDA_TIMER_IRQ_MASK_OSTIMER,
+		       base + RDA_TIMER_IRQ_MASK_CLR);
+
+	writel_relaxed(0, base + RDA_OSTIMER_CTRL);
+
+	return 0;
+}
+
+static int rda_ostimer_set_state_shutdown(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+
+	rda_ostimer_stop(timer_of_base(to));
+
+	return 0;
+}
+
+static int rda_ostimer_set_state_oneshot(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+
+	rda_ostimer_stop(timer_of_base(to));
+
+	return 0;
+}
+
+static int rda_ostimer_set_state_periodic(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+	unsigned long cycles_per_jiffy;
+
+	rda_ostimer_stop(timer_of_base(to));
+
+	cycles_per_jiffy = ((unsigned long long)NSEC_PER_SEC / HZ *
+			     evt->mult) >> evt->shift;
+	rda_ostimer_start(timer_of_base(to), true, cycles_per_jiffy);
+
+	return 0;
+}
+
+static int rda_ostimer_tick_resume(struct clock_event_device *evt)
+{
+	return 0;
+}
+
+static int rda_ostimer_set_next_event(unsigned long evt,
+				      struct clock_event_device *ev)
+{
+	struct timer_of *to = to_timer_of(ev);
+
+	rda_ostimer_start(timer_of_base(to), false, evt);
+
+	return 0;
+}
+
+static irqreturn_t rda_ostimer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+	struct timer_of *to = to_timer_of(evt);
+
+	/* clear timer int */
+	writel_relaxed(RDA_TIMER_IRQ_CLR_OSTIMER,
+		       timer_of_base(to) + RDA_TIMER_IRQ_CLR);
+
+	if (evt->event_handler)
+		evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct timer_of rda_ostimer_of = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_BASE,
+
+	.clkevt = {
+		.name = "rda-ostimer",
+		.rating = 250,
+		.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
+			    CLOCK_EVT_FEAT_DYNIRQ,
+		.set_state_shutdown = rda_ostimer_set_state_shutdown,
+		.set_state_oneshot = rda_ostimer_set_state_oneshot,
+		.set_state_periodic = rda_ostimer_set_state_periodic,
+		.tick_resume = rda_ostimer_tick_resume,
+		.set_next_event	= rda_ostimer_set_next_event,
+	},
+
+	.of_base = {
+		.name = "rda-timer",
+		.index = 0,
+	},
+
+	.of_irq = {
+		.name = "ostimer",
+		.handler = rda_ostimer_interrupt,
+		.flags = IRQF_TIMER,
+	},
+};
+
+static u64 rda_hwtimer_clocksource_read(void)
+{
+	void __iomem *base = timer_of_base(&rda_ostimer_of);
+	u32 lo, hi;
+
+	/* Always read low 32 bits first */
+	do {
+		lo = readl_relaxed(base + RDA_HWTIMER_LOCKVAL_L);
+		hi = readl_relaxed(base + RDA_HWTIMER_LOCKVAL_H);
+	} while (hi != readl_relaxed(base + RDA_HWTIMER_LOCKVAL_H));
+
+	return ((u64)hi << 32) | lo;
+}
+
+static u64 rda_hwtimer_read(struct clocksource *cs)
+{
+	return rda_hwtimer_clocksource_read();
+}
+
+static struct clocksource rda_hwtimer_clocksource = {
+	.name           = "rda-timer",
+	.rating         = 400,
+	.read           = rda_hwtimer_read,
+	.mask           = CLOCKSOURCE_MASK(64),
+	.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init rda_timer_init(struct device_node *np)
+{
+	unsigned long rate = 2000000;
+	int ret;
+
+	ret = timer_of_init(np, &rda_ostimer_of);
+	if (ret)
+		return ret;
+
+	clocksource_register_hz(&rda_hwtimer_clocksource, rate);
+	sched_clock_register(rda_hwtimer_clocksource_read, 64, rate);
+
+	clockevents_config_and_register(&rda_ostimer_of.clkevt, rate,
+					0x2, UINT_MAX);
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(rda8810pl, "rda,8810pl-timer", rda_timer_init);