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, 88 insertions, 0 deletions

diff --git a/drivers/interconnect/trace.h b/drivers/interconnect/trace.h
new file mode 100644
index 000000000..206373546
--- /dev/null
+++ b/drivers/interconnect/trace.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Interconnect framework tracepoints
+ * Copyright (c) 2019, Linaro Ltd.
+ * Author: Georgi Djakov <georgi.djakov@linaro.org>
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM interconnect
+
+#if !defined(_TRACE_INTERCONNECT_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_INTERCONNECT_H
+
+#include <linux/interconnect.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(icc_set_bw,
+
+	TP_PROTO(struct icc_path *p, struct icc_node *n, int i,
+		 u32 avg_bw, u32 peak_bw),
+
+	TP_ARGS(p, n, i, avg_bw, peak_bw),
+
+	TP_STRUCT__entry(
+		__string(path_name, p->name)
+		__string(dev, dev_name(p->reqs[i].dev))
+		__string(node_name, n->name)
+		__field(u32, avg_bw)
+		__field(u32, peak_bw)
+		__field(u32, node_avg_bw)
+		__field(u32, node_peak_bw)
+	),
+
+	TP_fast_assign(
+		__assign_str(path_name);
+		__assign_str(dev);
+		__assign_str(node_name);
+		__entry->avg_bw = avg_bw;
+		__entry->peak_bw = peak_bw;
+		__entry->node_avg_bw = n->avg_bw;
+		__entry->node_peak_bw = n->peak_bw;
+	),
+
+	TP_printk("path=%s dev=%s node=%s avg_bw=%u peak_bw=%u agg_avg=%u agg_peak=%u",
+		  __get_str(path_name),
+		  __get_str(dev),
+		  __get_str(node_name),
+		  __entry->avg_bw,
+		  __entry->peak_bw,
+		  __entry->node_avg_bw,
+		  __entry->node_peak_bw)
+);
+
+TRACE_EVENT(icc_set_bw_end,
+
+	TP_PROTO(struct icc_path *p, int ret),
+
+	TP_ARGS(p, ret),
+
+	TP_STRUCT__entry(
+		__string(path_name, p->name)
+		__string(dev, dev_name(p->reqs[0].dev))
+		__field(int, ret)
+	),
+
+	TP_fast_assign(
+		__assign_str(path_name);
+		__assign_str(dev);
+		__entry->ret = ret;
+	),
+
+	TP_printk("path=%s dev=%s ret=%d",
+		  __get_str(path_name),
+		  __get_str(dev),
+		  __entry->ret)
+);
+
+#endif /* _TRACE_INTERCONNECT_H */
+
+/* This part must be outside protection */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE trace
+
+#include <trace/define_trace.h>