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, 173 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-mp-csky.c b/drivers/clocksource/timer-mp-csky.c
new file mode 100644
index 000000000..183a99551
--- /dev/null
+++ b/drivers/clocksource/timer-mp-csky.c
@@ -0,0 +1,173 @@
+// 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 <linux/cpu.h>
+#include <linux/of_irq.h>
+#include <asm/reg_ops.h>
+
+#include "timer-of.h"
+
+#define PTIM_CCVR	"cr<3, 14>"
+#define PTIM_CTLR	"cr<0, 14>"
+#define PTIM_LVR	"cr<6, 14>"
+#define PTIM_TSR	"cr<1, 14>"
+
+static int csky_mptimer_irq;
+
+static int csky_mptimer_set_next_event(unsigned long delta,
+				       struct clock_event_device *ce)
+{
+	mtcr(PTIM_LVR, delta);
+
+	return 0;
+}
+
+static int csky_mptimer_shutdown(struct clock_event_device *ce)
+{
+	mtcr(PTIM_CTLR, 0);
+
+	return 0;
+}
+
+static int csky_mptimer_oneshot(struct clock_event_device *ce)
+{
+	mtcr(PTIM_CTLR, 1);
+
+	return 0;
+}
+
+static int csky_mptimer_oneshot_stopped(struct clock_event_device *ce)
+{
+	mtcr(PTIM_CTLR, 0);
+
+	return 0;
+}
+
+static DEFINE_PER_CPU(struct timer_of, csky_to) = {
+	.flags					= TIMER_OF_CLOCK,
+	.clkevt = {
+		.rating				= 300,
+		.features			= CLOCK_EVT_FEAT_PERCPU |
+						  CLOCK_EVT_FEAT_ONESHOT,
+		.set_state_shutdown		= csky_mptimer_shutdown,
+		.set_state_oneshot		= csky_mptimer_oneshot,
+		.set_state_oneshot_stopped	= csky_mptimer_oneshot_stopped,
+		.set_next_event			= csky_mptimer_set_next_event,
+	},
+};
+
+static irqreturn_t csky_timer_interrupt(int irq, void *dev)
+{
+	struct timer_of *to = this_cpu_ptr(&csky_to);
+
+	mtcr(PTIM_TSR, 0);
+
+	to->clkevt.event_handler(&to->clkevt);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * clock event for percpu
+ */
+static int csky_mptimer_starting_cpu(unsigned int cpu)
+{
+	struct timer_of *to = per_cpu_ptr(&csky_to, cpu);
+
+	to->clkevt.cpumask = cpumask_of(cpu);
+
+	enable_percpu_irq(csky_mptimer_irq, 0);
+
+	clockevents_config_and_register(&to->clkevt, timer_of_rate(to),
+					2, ULONG_MAX);
+
+	return 0;
+}
+
+static int csky_mptimer_dying_cpu(unsigned int cpu)
+{
+	disable_percpu_irq(csky_mptimer_irq);
+
+	return 0;
+}
+
+/*
+ * clock source
+ */
+static u64 notrace sched_clock_read(void)
+{
+	return (u64)mfcr(PTIM_CCVR);
+}
+
+static u64 clksrc_read(struct clocksource *c)
+{
+	return (u64)mfcr(PTIM_CCVR);
+}
+
+struct clocksource csky_clocksource = {
+	.name	= "csky",
+	.rating	= 400,
+	.mask	= CLOCKSOURCE_MASK(32),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.read	= clksrc_read,
+};
+
+static int __init csky_mptimer_init(struct device_node *np)
+{
+	int ret, cpu, cpu_rollback;
+	struct timer_of *to = NULL;
+
+	/*
+	 * Csky_mptimer is designed for C-SKY SMP multi-processors and
+	 * every core has it's own private irq and regs for clkevt and
+	 * clksrc.
+	 *
+	 * The regs is accessed by cpu instruction: mfcr/mtcr instead of
+	 * mmio map style. So we needn't mmio-address in dts, but we still
+	 * need to give clk and irq number.
+	 *
+	 * We use private irq for the mptimer and irq number is the same
+	 * for every core. So we use request_percpu_irq() in timer_of_init.
+	 */
+	csky_mptimer_irq = irq_of_parse_and_map(np, 0);
+	if (csky_mptimer_irq <= 0)
+		return -EINVAL;
+
+	ret = request_percpu_irq(csky_mptimer_irq, csky_timer_interrupt,
+				 "csky_mp_timer", &csky_to);
+	if (ret)
+		return -EINVAL;
+
+	for_each_possible_cpu(cpu) {
+		to = per_cpu_ptr(&csky_to, cpu);
+		ret = timer_of_init(np, to);
+		if (ret)
+			goto rollback;
+	}
+
+	clocksource_register_hz(&csky_clocksource, timer_of_rate(to));
+	sched_clock_register(sched_clock_read, 32, timer_of_rate(to));
+
+	ret = cpuhp_setup_state(CPUHP_AP_CSKY_TIMER_STARTING,
+				"clockevents/csky/timer:starting",
+				csky_mptimer_starting_cpu,
+				csky_mptimer_dying_cpu);
+	if (ret)
+		return -EINVAL;
+
+	return 0;
+
+rollback:
+	for_each_possible_cpu(cpu_rollback) {
+		if (cpu_rollback == cpu)
+			break;
+
+		to = per_cpu_ptr(&csky_to, cpu_rollback);
+		timer_of_cleanup(to);
+	}
+	return -EINVAL;
+}
+TIMER_OF_DECLARE(csky_mptimer, "csky,mptimer", csky_mptimer_init);