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, 72 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-of.h b/drivers/clocksource/timer-of.h
new file mode 100644
index 000000000..74a632b85
--- /dev/null
+++ b/drivers/clocksource/timer-of.h
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __TIMER_OF_H__
+#define __TIMER_OF_H__
+
+#include <linux/clockchips.h>
+
+#define TIMER_OF_BASE	0x1
+#define TIMER_OF_CLOCK	0x2
+#define TIMER_OF_IRQ	0x4
+
+struct of_timer_irq {
+	int irq;
+	int index;
+	const char *name;
+	unsigned long flags;
+	irq_handler_t handler;
+};
+
+struct of_timer_base {
+	void __iomem *base;
+	const char *name;
+	int index;
+};
+
+struct of_timer_clk {
+	struct clk *clk;
+	const char *name;
+	int index;
+	unsigned long rate;
+	unsigned long period;
+};
+
+struct timer_of {
+	unsigned int flags;
+	struct device_node *np;
+	struct clock_event_device clkevt;
+	struct of_timer_base of_base;
+	struct of_timer_irq  of_irq;
+	struct of_timer_clk  of_clk;
+	void *private_data;
+};
+
+static inline struct timer_of *to_timer_of(struct clock_event_device *clkevt)
+{
+	return container_of(clkevt, struct timer_of, clkevt);
+}
+
+static inline void __iomem *timer_of_base(struct timer_of *to)
+{
+	return to->of_base.base;
+}
+
+static inline int timer_of_irq(struct timer_of *to)
+{
+	return to->of_irq.irq;
+}
+
+static inline unsigned long timer_of_rate(struct timer_of *to)
+{
+	return to->of_clk.rate;
+}
+
+static inline unsigned long timer_of_period(struct timer_of *to)
+{
+	return to->of_clk.period;
+}
+
+int timer_of_init(struct device_node *np, struct timer_of *to);
+
+void timer_of_cleanup(struct timer_of *to);
+
+#endif