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, 53 insertions, 0 deletions

diff --git a/drivers/input/misc/ad714x.h b/drivers/input/misc/ad714x.h
new file mode 100644
index 000000000..dafa12325
--- /dev/null
+++ b/drivers/input/misc/ad714x.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * AD714X CapTouch Programmable Controller driver (bus interfaces)
+ *
+ * Copyright 2009-2011 Analog Devices Inc.
+ */
+
+#ifndef _AD714X_H_
+#define _AD714X_H_
+
+#include <linux/pm.h>
+#include <linux/types.h>
+
+#define STAGE_NUM              12
+
+struct device;
+struct ad714x_platform_data;
+struct ad714x_driver_data;
+struct ad714x_chip;
+
+typedef int (*ad714x_read_t)(struct ad714x_chip *, unsigned short, unsigned short *, size_t);
+typedef int (*ad714x_write_t)(struct ad714x_chip *, unsigned short, unsigned short);
+
+struct ad714x_chip {
+	unsigned short l_state;
+	unsigned short h_state;
+	unsigned short c_state;
+	unsigned short adc_reg[STAGE_NUM];
+	unsigned short amb_reg[STAGE_NUM];
+	unsigned short sensor_val[STAGE_NUM];
+
+	struct ad714x_platform_data *hw;
+	struct ad714x_driver_data *sw;
+
+	int irq;
+	struct device *dev;
+	ad714x_read_t read;
+	ad714x_write_t write;
+
+	struct mutex mutex;
+
+	unsigned product;
+	unsigned version;
+
+	__be16 xfer_buf[16] ____cacheline_aligned;
+
+};
+
+extern const struct dev_pm_ops ad714x_pm;
+struct ad714x_chip *ad714x_probe(struct device *dev, u16 bus_type, int irq,
+				 ad714x_read_t read, ad714x_write_t write);
+
+#endif