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, 267 insertions, 0 deletions

diff --git a/drivers/extcon/devres.c b/drivers/extcon/devres.c
new file mode 100644
index 000000000..f9d52e8ec
--- /dev/null
+++ b/drivers/extcon/devres.c
@@ -0,0 +1,267 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * drivers/extcon/devres.c - EXTCON device's resource management
+ *
+ * Copyright (C) 2016 Samsung Electronics
+ * Author: Chanwoo Choi <cw00.choi@samsung.com>
+ */
+
+#include "extcon.h"
+
+static int devm_extcon_dev_match(struct device *dev, void *res, void *data)
+{
+	struct extcon_dev **r = res;
+
+	if (WARN_ON(!r || !*r))
+		return 0;
+
+	return *r == data;
+}
+
+static void devm_extcon_dev_release(struct device *dev, void *res)
+{
+	extcon_dev_free(*(struct extcon_dev **)res);
+}
+
+
+static void devm_extcon_dev_unreg(struct device *dev, void *res)
+{
+	extcon_dev_unregister(*(struct extcon_dev **)res);
+}
+
+struct extcon_dev_notifier_devres {
+	struct extcon_dev *edev;
+	unsigned int id;
+	struct notifier_block *nb;
+};
+
+static void devm_extcon_dev_notifier_unreg(struct device *dev, void *res)
+{
+	struct extcon_dev_notifier_devres *this = res;
+
+	extcon_unregister_notifier(this->edev, this->id, this->nb);
+}
+
+static void devm_extcon_dev_notifier_all_unreg(struct device *dev, void *res)
+{
+	struct extcon_dev_notifier_devres *this = res;
+
+	extcon_unregister_notifier_all(this->edev, this->nb);
+}
+
+/**
+ * devm_extcon_dev_allocate - Allocate managed extcon device
+ * @dev:		the device owning the extcon device being created
+ * @supported_cable:	the array of the supported external connectors
+ *			ending with EXTCON_NONE.
+ *
+ * This function manages automatically the memory of extcon device using device
+ * resource management and simplify the control of freeing the memory of extcon
+ * device.
+ *
+ * Returns the pointer memory of allocated extcon_dev if success
+ * or ERR_PTR(err) if fail
+ */
+struct extcon_dev *devm_extcon_dev_allocate(struct device *dev,
+					const unsigned int *supported_cable)
+{
+	struct extcon_dev **ptr, *edev;
+
+	ptr = devres_alloc(devm_extcon_dev_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	edev = extcon_dev_allocate(supported_cable);
+	if (IS_ERR(edev)) {
+		devres_free(ptr);
+		return edev;
+	}
+
+	edev->dev.parent = dev;
+
+	*ptr = edev;
+	devres_add(dev, ptr);
+
+	return edev;
+}
+EXPORT_SYMBOL_GPL(devm_extcon_dev_allocate);
+
+/**
+ * devm_extcon_dev_free() - Resource-managed extcon_dev_unregister()
+ * @dev:	the device owning the extcon device being created
+ * @edev:	the extcon device to be freed
+ *
+ * Free the memory that is allocated with devm_extcon_dev_allocate()
+ * function.
+ */
+void devm_extcon_dev_free(struct device *dev, struct extcon_dev *edev)
+{
+	WARN_ON(devres_release(dev, devm_extcon_dev_release,
+			       devm_extcon_dev_match, edev));
+}
+EXPORT_SYMBOL_GPL(devm_extcon_dev_free);
+
+/**
+ * devm_extcon_dev_register() - Resource-managed extcon_dev_register()
+ * @dev:	the device owning the extcon device being created
+ * @edev:	the extcon device to be registered
+ *
+ * this function, that extcon device is automatically unregistered on driver
+ * detach. Internally this function calls extcon_dev_register() function.
+ * To get more information, refer that function.
+ *
+ * If extcon device is registered with this function and the device needs to be
+ * unregistered separately, devm_extcon_dev_unregister() should be used.
+ *
+ * Returns 0 if success or negaive error number if failure.
+ */
+int devm_extcon_dev_register(struct device *dev, struct extcon_dev *edev)
+{
+	struct extcon_dev **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_extcon_dev_unreg, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = extcon_dev_register(edev);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	*ptr = edev;
+	devres_add(dev, ptr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_extcon_dev_register);
+
+/**
+ * devm_extcon_dev_unregister() - Resource-managed extcon_dev_unregister()
+ * @dev:	the device owning the extcon device being created
+ * @edev:	the extcon device to unregistered
+ *
+ * Unregister extcon device that is registered with devm_extcon_dev_register()
+ * function.
+ */
+void devm_extcon_dev_unregister(struct device *dev, struct extcon_dev *edev)
+{
+	WARN_ON(devres_release(dev, devm_extcon_dev_unreg,
+			       devm_extcon_dev_match, edev));
+}
+EXPORT_SYMBOL_GPL(devm_extcon_dev_unregister);
+
+/**
+ * devm_extcon_register_notifier() - Resource-managed extcon_register_notifier()
+ * @dev:	the device owning the extcon device being created
+ * @edev:	the extcon device
+ * @id:		the unique id among the extcon enumeration
+ * @nb:		a notifier block to be registered
+ *
+ * This function manages automatically the notifier of extcon device using
+ * device resource management and simplify the control of unregistering
+ * the notifier of extcon device.
+ *
+ * Note that the second parameter given to the callback of nb (val) is
+ * "old_state", not the current state. The current state can be retrieved
+ * by looking at the third pameter (edev pointer)'s state value.
+ *
+ * Returns 0 if success or negaive error number if failure.
+ */
+int devm_extcon_register_notifier(struct device *dev, struct extcon_dev *edev,
+				unsigned int id, struct notifier_block *nb)
+{
+	struct extcon_dev_notifier_devres *ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_extcon_dev_notifier_unreg, sizeof(*ptr),
+				GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = extcon_register_notifier(edev, id, nb);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	ptr->edev = edev;
+	ptr->id = id;
+	ptr->nb = nb;
+	devres_add(dev, ptr);
+
+	return 0;
+}
+EXPORT_SYMBOL(devm_extcon_register_notifier);
+
+/**
+ * devm_extcon_unregister_notifier()
+ *			- Resource-managed extcon_unregister_notifier()
+ * @dev:	the device owning the extcon device being created
+ * @edev:	the extcon device
+ * @id:		the unique id among the extcon enumeration
+ * @nb:		a notifier block to be registered
+ */
+void devm_extcon_unregister_notifier(struct device *dev,
+				struct extcon_dev *edev, unsigned int id,
+				struct notifier_block *nb)
+{
+	WARN_ON(devres_release(dev, devm_extcon_dev_notifier_unreg,
+			       devm_extcon_dev_match, edev));
+}
+EXPORT_SYMBOL(devm_extcon_unregister_notifier);
+
+/**
+ * devm_extcon_register_notifier_all()
+ *		- Resource-managed extcon_register_notifier_all()
+ * @dev:	the device owning the extcon device being created
+ * @edev:	the extcon device
+ * @nb:		a notifier block to be registered
+ *
+ * This function manages automatically the notifier of extcon device using
+ * device resource management and simplify the control of unregistering
+ * the notifier of extcon device. To get more information, refer that function.
+ *
+ * Returns 0 if success or negaive error number if failure.
+ */
+int devm_extcon_register_notifier_all(struct device *dev, struct extcon_dev *edev,
+				struct notifier_block *nb)
+{
+	struct extcon_dev_notifier_devres *ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_extcon_dev_notifier_all_unreg, sizeof(*ptr),
+				GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = extcon_register_notifier_all(edev, nb);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	ptr->edev = edev;
+	ptr->nb = nb;
+	devres_add(dev, ptr);
+
+	return 0;
+}
+EXPORT_SYMBOL(devm_extcon_register_notifier_all);
+
+/**
+ * devm_extcon_unregister_notifier_all()
+ *		- Resource-managed extcon_unregister_notifier_all()
+ * @dev:	the device owning the extcon device being created
+ * @edev:	the extcon device
+ * @nb:		a notifier block to be registered
+ */
+void devm_extcon_unregister_notifier_all(struct device *dev,
+				struct extcon_dev *edev,
+				struct notifier_block *nb)
+{
+	WARN_ON(devres_release(dev, devm_extcon_dev_notifier_all_unreg,
+			       devm_extcon_dev_match, edev));
+}
+EXPORT_SYMBOL(devm_extcon_unregister_notifier_all);