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, 126 insertions, 0 deletions

diff --git a/drivers/reset/reset-brcmstb.c b/drivers/reset/reset-brcmstb.c
new file mode 100644
index 000000000..810fe7645
--- /dev/null
+++ b/drivers/reset/reset-brcmstb.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Broadcom STB generic reset controller for SW_INIT style reset controller
+ *
+ * Author: Florian Fainelli <f.fainelli@gmail.com>
+ * Copyright (C) 2018 Broadcom
+ */
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/types.h>
+
+struct brcmstb_reset {
+	void __iomem *base;
+	struct reset_controller_dev rcdev;
+};
+
+#define SW_INIT_SET		0x00
+#define SW_INIT_CLEAR		0x04
+#define SW_INIT_STATUS		0x08
+
+#define SW_INIT_BIT(id)		BIT((id) & 0x1f)
+#define SW_INIT_BANK(id)	((id) >> 5)
+
+/* A full bank contains extra registers that we are not utilizing but still
+ * qualify as a single bank.
+ */
+#define SW_INIT_BANK_SIZE	0x18
+
+static inline
+struct brcmstb_reset *to_brcmstb(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct brcmstb_reset, rcdev);
+}
+
+static int brcmstb_reset_assert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	unsigned int off = SW_INIT_BANK(id) * SW_INIT_BANK_SIZE;
+	struct brcmstb_reset *priv = to_brcmstb(rcdev);
+
+	writel_relaxed(SW_INIT_BIT(id), priv->base + off + SW_INIT_SET);
+
+	return 0;
+}
+
+static int brcmstb_reset_deassert(struct reset_controller_dev *rcdev,
+				  unsigned long id)
+{
+	unsigned int off = SW_INIT_BANK(id) * SW_INIT_BANK_SIZE;
+	struct brcmstb_reset *priv = to_brcmstb(rcdev);
+
+	writel_relaxed(SW_INIT_BIT(id), priv->base + off + SW_INIT_CLEAR);
+	/* Maximum reset delay after de-asserting a line and seeing block
+	 * operation is typically 14us for the worst case, build some slack
+	 * here.
+	 */
+	usleep_range(100, 200);
+
+	return 0;
+}
+
+static int brcmstb_reset_status(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	unsigned int off = SW_INIT_BANK(id) * SW_INIT_BANK_SIZE;
+	struct brcmstb_reset *priv = to_brcmstb(rcdev);
+
+	return readl_relaxed(priv->base + off + SW_INIT_STATUS) &
+			     SW_INIT_BIT(id);
+}
+
+static const struct reset_control_ops brcmstb_reset_ops = {
+	.assert	= brcmstb_reset_assert,
+	.deassert = brcmstb_reset_deassert,
+	.status = brcmstb_reset_status,
+};
+
+static int brcmstb_reset_probe(struct platform_device *pdev)
+{
+	struct device *kdev = &pdev->dev;
+	struct brcmstb_reset *priv;
+	struct resource *res;
+
+	priv = devm_kzalloc(kdev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	dev_set_drvdata(kdev, priv);
+
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = DIV_ROUND_DOWN_ULL(resource_size(res),
+						   SW_INIT_BANK_SIZE) * 32;
+	priv->rcdev.ops = &brcmstb_reset_ops;
+	priv->rcdev.of_node = kdev->of_node;
+	/* Use defaults: 1 cell and simple xlate function */
+
+	return devm_reset_controller_register(kdev, &priv->rcdev);
+}
+
+static const struct of_device_id brcmstb_reset_of_match[] = {
+	{ .compatible = "brcm,brcmstb-reset" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, brcmstb_reset_of_match);
+
+static struct platform_driver brcmstb_reset_driver = {
+	.probe	= brcmstb_reset_probe,
+	.driver	= {
+		.name = "brcmstb-reset",
+		.of_match_table = brcmstb_reset_of_match,
+	},
+};
+module_platform_driver(brcmstb_reset_driver);
+
+MODULE_AUTHOR("Broadcom");
+MODULE_DESCRIPTION("Broadcom STB reset controller");
+MODULE_LICENSE("GPL");