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, 79 insertions, 0 deletions

diff --git a/drivers/mfd/mp2629.c b/drivers/mfd/mp2629.c
new file mode 100644
index 000000000..717b704c3
--- /dev/null
+++ b/drivers/mfd/mp2629.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * MP2629 parent driver for ADC and battery charger
+ *
+ * Copyright 2020 Monolithic Power Systems, Inc
+ *
+ * Author: Saravanan Sekar <sravanhome@gmail.com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/mp2629.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+static const struct mfd_cell mp2629_cell[] = {
+	{
+		.name = "mp2629_adc",
+		.of_compatible = "mps,mp2629_adc",
+	},
+	{
+		.name = "mp2629_charger",
+		.of_compatible = "mps,mp2629_charger",
+	}
+};
+
+static const struct regmap_config mp2629_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0x17,
+};
+
+static int mp2629_probe(struct i2c_client *client)
+{
+	struct mp2629_data *ddata;
+	int ret;
+
+	ddata = devm_kzalloc(&client->dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	ddata->dev = &client->dev;
+	i2c_set_clientdata(client, ddata);
+
+	ddata->regmap = devm_regmap_init_i2c(client, &mp2629_regmap_config);
+	if (IS_ERR(ddata->regmap)) {
+		dev_err(ddata->dev, "Failed to allocate regmap\n");
+		return PTR_ERR(ddata->regmap);
+	}
+
+	ret = devm_mfd_add_devices(ddata->dev, PLATFORM_DEVID_AUTO, mp2629_cell,
+				   ARRAY_SIZE(mp2629_cell), NULL, 0, NULL);
+	if (ret)
+		dev_err(ddata->dev, "Failed to register sub-devices %d\n", ret);
+
+	return ret;
+}
+
+static const struct of_device_id mp2629_of_match[] = {
+	{ .compatible = "mps,mp2629"},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mp2629_of_match);
+
+static struct i2c_driver mp2629_driver = {
+	.driver = {
+		.name = "mp2629",
+		.of_match_table = mp2629_of_match,
+	},
+	.probe		= mp2629_probe,
+};
+module_i2c_driver(mp2629_driver);
+
+MODULE_AUTHOR("Saravanan Sekar <sravanhome@gmail.com>");
+MODULE_DESCRIPTION("MP2629 Battery charger parent driver");
+MODULE_LICENSE("GPL");