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, 47 insertions, 0 deletions

diff --git a/drivers/interconnect/internal.h b/drivers/interconnect/internal.h
new file mode 100644
index 000000000..3b9d50589
--- /dev/null
+++ b/drivers/interconnect/internal.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Interconnect framework internal structs
+ *
+ * Copyright (c) 2019, Linaro Ltd.
+ * Author: Georgi Djakov <georgi.djakov@linaro.org>
+ */
+
+#ifndef __DRIVERS_INTERCONNECT_INTERNAL_H
+#define __DRIVERS_INTERCONNECT_INTERNAL_H
+
+/**
+ * struct icc_req - constraints that are attached to each node
+ * @req_node: entry in list of requests for the particular @node
+ * @node: the interconnect node to which this constraint applies
+ * @dev: reference to the device that sets the constraints
+ * @enabled: indicates whether the path with this request is enabled
+ * @tag: path tag (optional)
+ * @avg_bw: an integer describing the average bandwidth in kBps
+ * @peak_bw: an integer describing the peak bandwidth in kBps
+ */
+struct icc_req {
+	struct hlist_node req_node;
+	struct icc_node *node;
+	struct device *dev;
+	bool enabled;
+	u32 tag;
+	u32 avg_bw;
+	u32 peak_bw;
+};
+
+/**
+ * struct icc_path - interconnect path structure
+ * @name: a string name of the path (useful for ftrace)
+ * @num_nodes: number of hops (nodes)
+ * @reqs: array of the requests applicable to this path of nodes
+ */
+struct icc_path {
+	const char *name;
+	size_t num_nodes;
+	struct icc_req reqs[] __counted_by(num_nodes);
+};
+
+struct icc_path *icc_get(struct device *dev, const char *src, const char *dst);
+int icc_debugfs_client_init(struct dentry *icc_dir);
+
+#endif