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, 165 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-ti-32k.c b/drivers/clocksource/timer-ti-32k.c
new file mode 100644
index 000000000..a86529a70
--- /dev/null
+++ b/drivers/clocksource/timer-ti-32k.c
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * timer-ti-32k.c - OMAP2 32k Timer Support
+ *
+ * Copyright (C) 2009 Nokia Corporation
+ *
+ * Update to use new clocksource/clockevent layers
+ * Author: Kevin Hilman, MontaVista Software, Inc. <source@mvista.com>
+ * Copyright (C) 2007 MontaVista Software, Inc.
+ *
+ * Original driver:
+ * Copyright (C) 2005 Nokia Corporation
+ * Author: Paul Mundt <paul.mundt@nokia.com>
+ *         Juha Yrjölä <juha.yrjola@nokia.com>
+ * OMAP Dual-mode timer framework support by Timo Teras
+ *
+ * Some parts based off of TI's 24xx code:
+ *
+ * Copyright (C) 2004-2009 Texas Instruments, Inc.
+ *
+ * Roughly modelled after the OMAP1 MPU timer code.
+ * Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
+ *
+ * Copyright (C) 2015 Texas Instruments Incorporated - https://www.ti.com
+ */
+
+#include <linux/clk.h>
+#include <linux/init.h>
+#include <linux/time.h>
+#include <linux/sched_clock.h>
+#include <linux/clocksource.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+
+/*
+ * 32KHz clocksource ... always available, on pretty most chips except
+ * OMAP 730 and 1510.  Other timers could be used as clocksources, with
+ * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
+ * but systems won't necessarily want to spend resources that way.
+ */
+
+#define OMAP2_32KSYNCNT_REV_OFF		0x0
+#define OMAP2_32KSYNCNT_REV_SCHEME	(0x3 << 30)
+#define OMAP2_32KSYNCNT_CR_OFF_LOW	0x10
+#define OMAP2_32KSYNCNT_CR_OFF_HIGH	0x30
+
+struct ti_32k {
+	void __iomem		*base;
+	void __iomem		*counter;
+	struct clocksource	cs;
+};
+
+static inline struct ti_32k *to_ti_32k(struct clocksource *cs)
+{
+	return container_of(cs, struct ti_32k, cs);
+}
+
+static u64 notrace ti_32k_read_cycles(struct clocksource *cs)
+{
+	struct ti_32k *ti = to_ti_32k(cs);
+
+	return (u64)readl_relaxed(ti->counter);
+}
+
+static struct ti_32k ti_32k_timer = {
+	.cs = {
+		.name		= "32k_counter",
+		.rating		= 250,
+		.read		= ti_32k_read_cycles,
+		.mask		= CLOCKSOURCE_MASK(32),
+		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+	},
+};
+
+static u64 notrace omap_32k_read_sched_clock(void)
+{
+	return ti_32k_read_cycles(&ti_32k_timer.cs);
+}
+
+static void __init ti_32k_timer_enable_clock(struct device_node *np,
+					     const char *name)
+{
+	struct clk *clock;
+	int error;
+
+	clock = of_clk_get_by_name(np->parent, name);
+	if (IS_ERR(clock)) {
+		/* Only some SoCs have a separate interface clock */
+		if (PTR_ERR(clock) == -EINVAL && !strncmp("ick", name, 3))
+			return;
+
+		pr_warn("%s: could not get clock %s %li\n",
+			__func__, name, PTR_ERR(clock));
+		return;
+	}
+
+	error = clk_prepare_enable(clock);
+	if (error) {
+		pr_warn("%s: could not enable %s: %i\n",
+			__func__, name, error);
+		return;
+	}
+}
+
+static void __init ti_32k_timer_module_init(struct device_node *np,
+					    void __iomem *base)
+{
+	void __iomem *sysc = base + 4;
+
+	if (!of_device_is_compatible(np->parent, "ti,sysc"))
+		return;
+
+	ti_32k_timer_enable_clock(np, "fck");
+	ti_32k_timer_enable_clock(np, "ick");
+
+	/*
+	 * Force idle module as wkup domain is active with MPU.
+	 * No need to tag the module disabled for ti-sysc probe.
+	 */
+	writel_relaxed(0, sysc);
+}
+
+static int __init ti_32k_timer_init(struct device_node *np)
+{
+	int ret;
+
+	ti_32k_timer.base = of_iomap(np, 0);
+	if (!ti_32k_timer.base) {
+		pr_err("Can't ioremap 32k timer base\n");
+		return -ENXIO;
+	}
+
+	if (!of_machine_is_compatible("ti,am43"))
+		ti_32k_timer.cs.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;
+
+	ti_32k_timer.counter = ti_32k_timer.base;
+	ti_32k_timer_module_init(np, ti_32k_timer.base);
+
+	/*
+	 * 32k sync Counter IP register offsets vary between the highlander
+	 * version and the legacy ones.
+	 *
+	 * The 'SCHEME' bits(30-31) of the revision register is used to identify
+	 * the version.
+	 */
+	if (readl_relaxed(ti_32k_timer.base + OMAP2_32KSYNCNT_REV_OFF) &
+			OMAP2_32KSYNCNT_REV_SCHEME)
+		ti_32k_timer.counter += OMAP2_32KSYNCNT_CR_OFF_HIGH;
+	else
+		ti_32k_timer.counter += OMAP2_32KSYNCNT_CR_OFF_LOW;
+
+	pr_info("OMAP clocksource: 32k_counter at 32768 Hz\n");
+
+	ret = clocksource_register_hz(&ti_32k_timer.cs, 32768);
+	if (ret) {
+		pr_err("32k_counter: can't register clocksource\n");
+		return ret;
+	}
+
+	sched_clock_register(omap_32k_read_sched_clock, 32, 32768);
+
+	return 0;
+}
+TIMER_OF_DECLARE(ti_32k_timer, "ti,omap-counter32k",
+		ti_32k_timer_init);