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

11 files changed, 469 insertions, 0 deletions

diff --git a/Documentation/tools/rv/Makefile b/Documentation/tools/rv/Makefile
new file mode 100644
index 000000000..ec8713c1b
--- /dev/null
+++ b/Documentation/tools/rv/Makefile
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+INSTALL		?= install
+RM		?= rm -f
+RMDIR		?= rmdir --ignore-fail-on-non-empty
+
+PREFIX		?= /usr/share
+MANDIR		?= $(PREFIX)/man
+MAN1DIR		= $(MANDIR)/man1
+
+MAN1_RST	= $(wildcard rv*.rst)
+
+_DOC_MAN1	= $(patsubst %.rst,%.1,$(MAN1_RST))
+DOC_MAN1	= $(addprefix $(OUTPUT),$(_DOC_MAN1))
+
+RST2MAN_DEP	:= $(shell command -v rst2man 2>/dev/null)
+RST2MAN_OPTS	+= --verbose
+
+TEST_RST2MAN = $(shell sh -c "rst2man --version > /dev/null 2>&1 || echo n")
+
+$(OUTPUT)%.1: %.rst
+ifndef RST2MAN_DEP
+	$(info ********************************************)
+	$(info ** NOTICE: rst2man not found)
+	$(info **)
+	$(info ** Consider installing the latest rst2man from your)
+	$(info ** distribution, e.g., 'dnf install python3-docutils' on Fedora,)
+	$(info ** or from source:)
+	$(info **)
+	$(info **  https://docutils.sourceforge.io/docs/dev/repository.html )
+	$(info **)
+	$(info ********************************************)
+	$(error NOTICE: rst2man required to generate man pages)
+endif
+	rst2man $(RST2MAN_OPTS) $< > $@
+
+man1: $(DOC_MAN1)
+man: man1
+
+clean:
+	$(RM) $(DOC_MAN1)
+
+install: man
+	$(INSTALL) -d -m 755 $(DESTDIR)$(MAN1DIR)
+	$(INSTALL) -m 644 $(DOC_MAN1) $(DESTDIR)$(MAN1DIR)
+
+uninstall:
+	$(RM) $(addprefix $(DESTDIR)$(MAN1DIR)/,$(_DOC_MAN1))
+	$(RMDIR) $(DESTDIR)$(MAN1DIR)
+
+.PHONY: man man1 clean install uninstall
+.DEFAULT_GOAL := man
diff --git a/Documentation/tools/rv/common_appendix.rst b/Documentation/tools/rv/common_appendix.rst
new file mode 100644
index 000000000..f4239192b
--- /dev/null
+++ b/Documentation/tools/rv/common_appendix.rst
@@ -0,0 +1,16 @@
+REPORTING BUGS
+==============
+
+Report bugs to <linux-kernel@vger.kernel.org>
+and <linux-trace-devel@vger.kernel.org>
+
+LICENSE
+=======
+
+**rv** is Free Software licensed under the GNU GPLv2
+
+COPYING
+=======
+
+Copyright \(C) 2022 Red Hat, Inc. Free use of this software is granted under
+the terms of the GNU Public License (GPL).
diff --git a/Documentation/tools/rv/common_ikm.rst b/Documentation/tools/rv/common_ikm.rst
new file mode 100644
index 000000000..e50a5f8a7
--- /dev/null
+++ b/Documentation/tools/rv/common_ikm.rst
@@ -0,0 +1,21 @@
+**-h**, **--help**
+
+        Print the monitor's options and the available reactors list.
+
+**-r**, **--reactor** *reactor*
+
+        Enables the *reactor*. See **-h** for a list of available reactors.
+
+**-s**, **--self**
+
+        When tracing (**-t**), also print the events that happened during the **rv**
+        command itself. If the **rv** command itself generates too many events,
+        the tool might get busy processing its own events only.
+
+**-t**, **--trace**
+
+        Trace monitor's events and error.
+
+**-v**, **--verbose**
+
+        Print debug messages.
diff --git a/Documentation/tools/rv/index.rst b/Documentation/tools/rv/index.rst
new file mode 100644
index 000000000..2aaa01c9f
--- /dev/null
+++ b/Documentation/tools/rv/index.rst
@@ -0,0 +1,19 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================
+Runtime verification (rv) tool
+==============================
+
+**rv** tool provides the interface for a collection of runtime verification
+(rv) monitors.
+
+.. toctree::
+   :maxdepth: 1
+
+   rv
+   rv-list
+   rv-mon
+   rv-mon-wip
+   rv-mon-wwnr
+   rv-mon-sched
+   rv-mon-stall
diff --git a/Documentation/tools/rv/rv-list.rst b/Documentation/tools/rv/rv-list.rst
new file mode 100644
index 000000000..51e4608f9
--- /dev/null
+++ b/Documentation/tools/rv/rv-list.rst
@@ -0,0 +1,43 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======
+rv-list
+=======
+-----------------------
+List available monitors
+-----------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+
+**rv list** [*OPTIONS*]
+
+DESCRIPTION
+===========
+
+The **rv list** command prints all available monitors. These monitors
+can be enabled using the **rv mon** command.
+
+OPTIONS
+=======
+
+**-h**, **--help**
+
+        Print help menu.
+
+SEE ALSO
+========
+
+**rv**\(1), **rv-mon**\(1)
+
+Linux kernel *RV* documentation:
+<https://www.kernel.org/doc/html/latest/trace/rv/index.html>
+
+AUTHOR
+======
+
+Written by Daniel Bristot de Oliveira <bristot@kernel.org>
+
+.. include:: common_appendix.rst
diff --git a/Documentation/tools/rv/rv-mon-sched.rst b/Documentation/tools/rv/rv-mon-sched.rst
new file mode 100644
index 000000000..da0fe4c79
--- /dev/null
+++ b/Documentation/tools/rv/rv-mon-sched.rst
@@ -0,0 +1,69 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+rv-mon-sched
+============
+-----------------------------
+Scheduler monitors collection
+-----------------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+
+**rv mon sched** [*OPTIONS*]
+
+**rv mon <NESTED_MONITOR>** [*OPTIONS*]
+
+**rv mon sched:<NESTED_MONITOR>** [*OPTIONS*]
+
+DESCRIPTION
+===========
+
+The scheduler monitor collection is a container for several monitors to model
+the behaviour of the scheduler. Each monitor describes a specification that
+the scheduler should follow.
+
+As a monitor container, it will enable all nested monitors and set them
+according to OPTIONS.
+Nevertheless nested monitors can also be activated independently both by name
+and by specifying sched: , e.g. to enable only monitor tss you can do any of:
+
+    # rv mon sched:tss
+
+    # rv mon tss
+
+See kernel documentation for further information about this monitor:
+<https://docs.kernel.org/trace/rv/monitor_sched.html>
+
+OPTIONS
+=======
+
+.. include:: common_ikm.rst
+
+NESTED MONITOR
+==============
+
+The available nested monitors are:
+  * scpd: schedule called with preemption disabled
+  * snep: schedule does not enable preempt
+  * sncid: schedule not called with interrupt disabled
+  * snroc: set non runnable on its own context
+  * sco: scheduling context operations
+  * tss: task switch while scheduling
+
+SEE ALSO
+========
+
+**rv**\(1), **rv-mon**\(1)
+
+Linux kernel *RV* documentation:
+<https://www.kernel.org/doc/html/latest/trace/rv/index.html>
+
+AUTHOR
+======
+
+Written by Gabriele Monaco <gmonaco@redhat.com>
+
+.. include:: common_appendix.rst
diff --git a/Documentation/tools/rv/rv-mon-stall.rst b/Documentation/tools/rv/rv-mon-stall.rst
new file mode 100644
index 000000000..c79d7c2e4
--- /dev/null
+++ b/Documentation/tools/rv/rv-mon-stall.rst
@@ -0,0 +1,44 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+rv-mon-stall
+============
+--------------------
+Stalled task monitor
+--------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+
+**rv mon stall** [*OPTIONS*]
+
+DESCRIPTION
+===========
+
+The stalled task (**stall**) monitor is a sample per-task timed monitor that
+checks if tasks are scheduled within a defined threshold after they are ready.
+
+See kernel documentation for further information about this monitor:
+<https://docs.kernel.org/trace/rv/monitor_stall.html>
+
+OPTIONS
+=======
+
+.. include:: common_ikm.rst
+
+SEE ALSO
+========
+
+**rv**\(1), **rv-mon**\(1)
+
+Linux kernel *RV* documentation:
+<https://www.kernel.org/doc/html/latest/trace/rv/index.html>
+
+AUTHOR
+======
+
+Written by Gabriele Monaco <gmonaco@redhat.com>
+
+.. include:: common_appendix.rst
diff --git a/Documentation/tools/rv/rv-mon-wip.rst b/Documentation/tools/rv/rv-mon-wip.rst
new file mode 100644
index 000000000..2d42104d6
--- /dev/null
+++ b/Documentation/tools/rv/rv-mon-wip.rst
@@ -0,0 +1,44 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========
+rv-mon-wip
+==========
+----------------------------
+Wakeup In Preemptive monitor
+----------------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+
+**rv mon wip** [*OPTIONS*]
+
+DESCRIPTION
+===========
+
+The wakeup in preemptive (**wip**) monitor is a sample per-cpu monitor that
+checks if the wakeup events always take place with preemption disabled.
+
+See kernel documentation for further information about this monitor:
+<https://docs.kernel.org/trace/rv/monitor_wip.html>
+
+OPTIONS
+=======
+
+.. include:: common_ikm.rst
+
+SEE ALSO
+========
+
+**rv**\(1), **rv-mon**\(1)
+
+Linux kernel *RV* documentation:
+<https://www.kernel.org/doc/html/latest/trace/rv/index.html>
+
+AUTHOR
+======
+
+Written by Daniel Bristot de Oliveira <bristot@kernel.org>
+
+.. include:: common_appendix.rst
diff --git a/Documentation/tools/rv/rv-mon-wwnr.rst b/Documentation/tools/rv/rv-mon-wwnr.rst
new file mode 100644
index 000000000..a18f3fd54
--- /dev/null
+++ b/Documentation/tools/rv/rv-mon-wwnr.rst
@@ -0,0 +1,43 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========
+rv-mon-wwnr
+===========
+--------------------------------
+Wakeup While Not Running monitor
+--------------------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+
+**rv mon wip** [*OPTIONS*]
+
+DESCRIPTION
+===========
+
+The wakeup while not running (**wwnr**) is a per-task sample monitor.
+
+See kernel documentation for further information about this monitor:
+<https://docs.kernel.org/trace/rv/monitor_wwnr.html>
+
+OPTIONS
+=======
+
+.. include:: common_ikm.rst
+
+SEE ALSO
+========
+
+**rv**\(1), **rv-mon**\(1)
+
+Linux kernel *RV* documentation:
+<https://www.kernel.org/doc/html/latest/trace/rv/index.html>
+
+AUTHOR
+======
+
+Written by Daniel Bristot de Oliveira <bristot@kernel.org>
+
+.. include:: common_appendix.rst
diff --git a/Documentation/tools/rv/rv-mon.rst b/Documentation/tools/rv/rv-mon.rst
new file mode 100644
index 000000000..4d86fd55e
--- /dev/null
+++ b/Documentation/tools/rv/rv-mon.rst
@@ -0,0 +1,55 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======
+rv-mon
+======
+-----------------------
+List available monitors
+-----------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+
+**rv mon** [*-h*] **monitor_name** [*-h*] [*MONITOR OPTIONS*]
+
+DESCRIPTION
+===========
+
+The **rv mon** command runs the monitor named *monitor_name*. Each monitor
+has its own set of options. The **rv list** command shows all available
+monitors.
+
+OPTIONS
+=======
+
+**-h**, **--help**
+
+        Print help menu.
+
+AVAILABLE MONITORS
+==================
+
+The **rv** tool provides the interface for a set of monitors. Use the
+**rv list** command to list all available monitors.
+
+Each monitor has its own set of options. See man **rv-mon**-*monitor_name*
+for details about each specific monitor. Also, running **rv mon**
+**monitor_name** **-h** display the help menu with the available
+options.
+
+SEE ALSO
+========
+
+**rv**\(1), **rv-mon**\(1)
+
+Linux kernel *RV* documentation:
+<https://www.kernel.org/doc/html/latest/trace/rv/index.html>
+
+AUTHOR
+======
+
+Written by Daniel Bristot de Oliveira <bristot@kernel.org>
+
+.. include:: common_appendix.rst
diff --git a/Documentation/tools/rv/rv.rst b/Documentation/tools/rv/rv.rst
new file mode 100644
index 000000000..cee93dc21
--- /dev/null
+++ b/Documentation/tools/rv/rv.rst
@@ -0,0 +1,63 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==
+rv
+==
+--------------------
+Runtime Verification
+--------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+
+**rv** *COMMAND* [*OPTIONS*]
+
+DESCRIPTION
+===========
+
+Runtime Verification (**RV**) is a lightweight (yet rigorous) method
+for formal verification with a practical approach for complex systems.
+Instead of relying on a fine-grained model of a system (e.g., a
+re-implementation a instruction level), RV works by analyzing the trace
+of the system's actual execution, comparing it against a formal
+specification of the system behavior.
+
+The **rv** tool provides the interface for a collection of runtime
+verification (rv) monitors.
+
+COMMANDS
+========
+
+**list**
+
+        List all available monitors.
+
+**mon**
+
+        Run monitor.
+
+OPTIONS
+=======
+
+**-h**, **--help**
+
+        Display the help text.
+
+For other options, see the man page for the corresponding command.
+
+SEE ALSO
+========
+
+**rv-list**\(1), **rv-mon**\(1)
+
+Linux kernel *RV* documentation:
+<https://www.kernel.org/doc/html/latest/trace/rv/index.html>
+
+AUTHOR
+======
+
+Daniel Bristot de Oliveira <bristot@kernel.org>
+
+.. include:: common_appendix.rst