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, 96 insertions, 0 deletions

diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
new file mode 100644
index 000000000..a8b7065fd
--- /dev/null
+++ b/drivers/rpmsg/rpmsg_internal.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * remote processor messaging bus internals
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <ohad@wizery.com>
+ * Brian Swetland <swetland@google.com>
+ */
+
+#ifndef __RPMSG_INTERNAL_H__
+#define __RPMSG_INTERNAL_H__
+
+#include <linux/rpmsg.h>
+#include <linux/poll.h>
+
+#define to_rpmsg_device(d) container_of(d, struct rpmsg_device, dev)
+#define to_rpmsg_driver(d) container_of_const(d, struct rpmsg_driver, drv)
+
+extern const struct class rpmsg_class;
+
+/**
+ * struct rpmsg_device_ops - indirection table for the rpmsg_device operations
+ * @create_channel:	create backend-specific channel, optional
+ * @release_channel:	release backend-specific channel, optional
+ * @create_ept:		create backend-specific endpoint, required
+ * @announce_create:	announce presence of new channel, optional
+ * @announce_destroy:	announce destruction of channel, optional
+ *
+ * Indirection table for the operations that a rpmsg backend should implement.
+ * @announce_create and @announce_destroy are optional as the backend might
+ * advertise new channels implicitly by creating the endpoints.
+ */
+struct rpmsg_device_ops {
+	struct rpmsg_device *(*create_channel)(struct rpmsg_device *rpdev,
+					       struct rpmsg_channel_info *chinfo);
+	int (*release_channel)(struct rpmsg_device *rpdev,
+			       struct rpmsg_channel_info *chinfo);
+	struct rpmsg_endpoint *(*create_ept)(struct rpmsg_device *rpdev,
+					    rpmsg_rx_cb_t cb, void *priv,
+					    struct rpmsg_channel_info chinfo);
+
+	int (*announce_create)(struct rpmsg_device *rpdev);
+	int (*announce_destroy)(struct rpmsg_device *rpdev);
+};
+
+/**
+ * struct rpmsg_endpoint_ops - indirection table for rpmsg_endpoint operations
+ * @destroy_ept:	see @rpmsg_destroy_ept(), required
+ * @send:		see @rpmsg_send(), required
+ * @sendto:		see @rpmsg_sendto(), optional
+ * @trysend:		see @rpmsg_trysend(), required
+ * @trysendto:		see @rpmsg_trysendto(), optional
+ * @poll:		see @rpmsg_poll(), optional
+ * @set_flow_control:	see @rpmsg_set_flow_control(), optional
+ * @get_mtu:		see @rpmsg_get_mtu(), optional
+ *
+ * Indirection table for the operations that a rpmsg backend should implement.
+ * In addition to @destroy_ept, the backend must at least implement @send and
+ * @trysend, while the variants sending data off-channel are optional.
+ */
+struct rpmsg_endpoint_ops {
+	void (*destroy_ept)(struct rpmsg_endpoint *ept);
+
+	int (*send)(struct rpmsg_endpoint *ept, const void *data, int len);
+	int (*sendto)(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst);
+
+	int (*trysend)(struct rpmsg_endpoint *ept, const void *data, int len);
+	int (*trysendto)(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst);
+	__poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
+			     poll_table *wait);
+	int (*set_flow_control)(struct rpmsg_endpoint *ept, bool pause, u32 dst);
+	ssize_t (*get_mtu)(struct rpmsg_endpoint *ept);
+};
+
+struct device *rpmsg_find_device(struct device *parent,
+				 struct rpmsg_channel_info *chinfo);
+
+struct rpmsg_device *rpmsg_create_channel(struct rpmsg_device *rpdev,
+					  struct rpmsg_channel_info *chinfo);
+int rpmsg_release_channel(struct rpmsg_device *rpdev,
+			  struct rpmsg_channel_info *chinfo);
+/**
+ * rpmsg_ctrldev_register_device() - register a char device for control based on rpdev
+ * @rpdev:	prepared rpdev to be used for creating endpoints
+ *
+ * This function wraps rpmsg_register_device() preparing the rpdev for use as
+ * basis for the rpmsg chrdev.
+ */
+static inline int rpmsg_ctrldev_register_device(struct rpmsg_device *rpdev)
+{
+	return rpmsg_register_device_override(rpdev, "rpmsg_ctrl");
+}
+
+#endif