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, 111 insertions, 0 deletions

diff --git a/drivers/reset/reset-berlin.c b/drivers/reset/reset-berlin.c
new file mode 100644
index 000000000..578fe8670
--- /dev/null
+++ b/drivers/reset/reset-berlin.c
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2014 Marvell Technology Group Ltd.
+ *
+ * Marvell Berlin reset driver
+ *
+ * Antoine Tenart <antoine.tenart@free-electrons.com>
+ * Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#define BERLIN_MAX_RESETS	32
+
+#define to_berlin_reset_priv(p)		\
+	container_of((p), struct berlin_reset_priv, rcdev)
+
+struct berlin_reset_priv {
+	struct regmap			*regmap;
+	struct reset_controller_dev	rcdev;
+};
+
+static int berlin_reset_reset(struct reset_controller_dev *rcdev,
+			      unsigned long id)
+{
+	struct berlin_reset_priv *priv = to_berlin_reset_priv(rcdev);
+	int offset = id >> 8;
+	int mask = BIT(id & 0x1f);
+
+	regmap_write(priv->regmap, offset, mask);
+
+	/* let the reset be effective */
+	udelay(10);
+
+	return 0;
+}
+
+static const struct reset_control_ops berlin_reset_ops = {
+	.reset	= berlin_reset_reset,
+};
+
+static int berlin_reset_xlate(struct reset_controller_dev *rcdev,
+			      const struct of_phandle_args *reset_spec)
+{
+	unsigned int offset, bit;
+
+	offset = reset_spec->args[0];
+	bit = reset_spec->args[1];
+
+	if (bit >= BERLIN_MAX_RESETS)
+		return -EINVAL;
+
+	return (offset << 8) | bit;
+}
+
+static int berlin2_reset_probe(struct platform_device *pdev)
+{
+	struct device_node *parent_np;
+	struct berlin_reset_priv *priv;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	parent_np = of_get_parent(pdev->dev.of_node);
+	priv->regmap = syscon_node_to_regmap(parent_np);
+	of_node_put(parent_np);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.ops = &berlin_reset_ops;
+	priv->rcdev.of_node = pdev->dev.of_node;
+	priv->rcdev.of_reset_n_cells = 2;
+	priv->rcdev.of_xlate = berlin_reset_xlate;
+
+	return reset_controller_register(&priv->rcdev);
+}
+
+static const struct of_device_id berlin_reset_dt_match[] = {
+	{ .compatible = "marvell,berlin2-reset" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, berlin_reset_dt_match);
+
+static struct platform_driver berlin_reset_driver = {
+	.probe	= berlin2_reset_probe,
+	.driver	= {
+		.name = "berlin2-reset",
+		.of_match_table = berlin_reset_dt_match,
+	},
+};
+module_platform_driver(berlin_reset_driver);
+
+MODULE_AUTHOR("Antoine Tenart <antoine.tenart@free-electrons.com>");
+MODULE_AUTHOR("Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>");
+MODULE_DESCRIPTION("Synaptics Berlin reset controller");
+MODULE_LICENSE("GPL");