[xfsprogs PATCH v3 3/3] xfs_io: add a new 'log_writes' command

[Ross Zwisler <ross.zwisler@linux.intel.com>]

Add a new 'log_writes' command to xfs_io so that we can add dm-log-writes
log marks.  It's helpful to allow users of xfs_io to adds these marks from
within xfs_io instead of waiting until after xfs_io exits because then they
are able to replay the dm-log-writes log up to immediately after another
xfs_io operation such as mwrite.  This isolates the log replay from other
operations that happen as part of xfs_io exiting (file handles being
closed, mmaps being torn down, etc.).  This also allows users to insert
multiple marks between different xfs_io commands.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
---

Changes from v2:
 - Use 'exitcode' to have the xfs_io shell command error out with status
   1 if we hit any of our many error condtions during execution. (Dave)

---
 configure.ac            |   1 +
 debian/control          |   2 +-
 include/builddefs.in    |   2 +
 io/Makefile             |   6 +++
 io/init.c               |   1 +
 io/io.h                 |   6 +++
 io/log_writes.c         | 106 ++++++++++++++++++++++++++++++++++++++++++++++++
 m4/Makefile             |   1 +
 m4/package_devmapper.m4 |  11 +++++
 man/man8/xfs_io.8       |  23 ++++++++++-
 10 files changed, 157 insertions(+), 2 deletions(-)
 create mode 100644 io/log_writes.c
 create mode 100644 m4/package_devmapper.m4

diff --git a/configure.ac b/configure.ac
index f3325aa0..f83d5817 100644
--- a/configure.ac
+++ b/configure.ac
@@ -164,6 +164,7 @@ AC_NEED_INTERNAL_FSXATTR
 AC_HAVE_GETFSMAP
 AC_HAVE_STATFS_FLAGS
 AC_HAVE_MAP_SYNC
+AC_HAVE_DEVMAPPER
 
 if test "$enable_blkid" = yes; then
 AC_HAVE_BLKID_TOPO
diff --git a/debian/control b/debian/control
index ad816622..5c26e3d7 100644
--- a/debian/control
+++ b/debian/control
@@ -3,7 +3,7 @@ Section: admin
 Priority: optional
 Maintainer: XFS Development Team <linux-xfs@vger.kernel.org>
 Uploaders: Nathan Scott <nathans@debian.org>, Anibal Monsalve Salazar <anibal@debian.org>
-Build-Depends: uuid-dev, dh-autoreconf, debhelper (>= 5), gettext, libtool, libreadline-gplv2-dev | libreadline5-dev, libblkid-dev (>= 2.17), linux-libc-dev
+Build-Depends: uuid-dev, dh-autoreconf, debhelper (>= 5), gettext, libtool, libreadline-gplv2-dev | libreadline5-dev, libblkid-dev (>= 2.17), linux-libc-dev, libdevmapper-dev
 Standards-Version: 3.9.1
 Homepage: http://xfs.org/
 
diff --git a/include/builddefs.in b/include/builddefs.in
index 126f7e95..66bdbfa2 100644
--- a/include/builddefs.in
+++ b/include/builddefs.in
@@ -35,6 +35,7 @@ LIBTERMCAP = @libtermcap@
 LIBEDITLINE = @libeditline@
 LIBREADLINE = @libreadline@
 LIBBLKID = @libblkid@
+LIBDEVMAPPER = @libdevmapper@
 LIBXFS = $(TOPDIR)/libxfs/libxfs.la
 LIBXCMD = $(TOPDIR)/libxcmd/libxcmd.la
 LIBXLOG = $(TOPDIR)/libxlog/libxlog.la
@@ -116,6 +117,7 @@ NEED_INTERNAL_FSXATTR = @need_internal_fsxattr@
 HAVE_GETFSMAP = @have_getfsmap@
 HAVE_STATFS_FLAGS = @have_statfs_flags@
 HAVE_MAP_SYNC = @have_map_sync@
+HAVE_DEVMAPPER = @have_devmapper@
 
 GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall
 #	   -Wbitwise -Wno-transparent-union -Wno-old-initializer -Wno-decl
diff --git a/io/Makefile b/io/Makefile
index 2987ee11..b7585a1b 100644
--- a/io/Makefile
+++ b/io/Makefile
@@ -107,6 +107,12 @@ ifeq ($(HAVE_MAP_SYNC),yes)
 LCFLAGS += -DHAVE_MAP_SYNC
 endif
 
+ifeq ($(HAVE_DEVMAPPER),yes)
+CFILES += log_writes.c
+LLDLIBS += $(LIBDEVMAPPER)
+LCFLAGS += -DHAVE_DEVMAPPER
+endif
+
 # On linux we get fsmap from the system or define it ourselves
 # so include this based on platform type.  If this reverts to only
 # the autoconf check w/o local definition, change to testing HAVE_GETFSMAP
diff --git a/io/init.c b/io/init.c
index 20d5f80d..34d87b5f 100644
--- a/io/init.c
+++ b/io/init.c
@@ -72,6 +72,7 @@ init_commands(void)
 	help_init();
 	imap_init();
 	inject_init();
+	log_writes_init();
 	madvise_init();
 	mincore_init();
 	mmap_init();
diff --git a/io/io.h b/io/io.h
index 8b2753b3..9349cc75 100644
--- a/io/io.h
+++ b/io/io.h
@@ -186,3 +186,9 @@ extern void		fsmap_init(void);
 #else
 # define fsmap_init()	do { } while (0)
 #endif
+
+#ifdef HAVE_DEVMAPPER
+extern void		log_writes_init(void);
+#else
+#define log_writes_init()	do { } while (0)
+#endif
diff --git a/io/log_writes.c b/io/log_writes.c
new file mode 100644
index 00000000..c7b7392e
--- /dev/null
+++ b/io/log_writes.c
@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2017 Intel Corporation.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include "platform_defs.h"
+#include <libdevmapper.h>
+#include "command.h"
+#include "init.h"
+
+static cmdinfo_t log_writes_cmd;
+
+static int
+mark_log(const char *device, const char *mark)
+{
+	struct dm_task *dmt;
+	const int size = 80;
+	char message[size];
+	int len, ret = 0;
+
+	len = snprintf(message, size, "mark %s", mark);
+	if (len >= size) {
+		printf("mark '%s' is too long\n", mark);
+		return ret;
+	}
+
+	if (!(dmt = dm_task_create(DM_DEVICE_TARGET_MSG)))
+		return ret;
+
+	if (!dm_task_set_name(dmt, device))
+		goto out;
+
+	if (!dm_task_set_sector(dmt, 0))
+		goto out;
+
+	if (!dm_task_set_message(dmt, message))
+		goto out;
+
+	if (dm_task_run(dmt))
+		ret = 1;
+out:
+	dm_task_destroy(dmt);
+	return ret;
+}
+
+static int
+log_writes_f(
+	int			argc,
+	char			**argv)
+{
+	const char *device = NULL;
+	const char *mark = NULL;
+	int c;
+
+	exitcode = 1;
+	while ((c = getopt(argc, argv, "d:m:")) != EOF) {
+		switch (c) {
+		case 'd':
+			device = optarg;
+			break;
+		case 'm':
+			mark = optarg;
+			break;
+		default:
+			return command_usage(&log_writes_cmd);
+		}
+	}
+
+	if (device == NULL || mark == NULL)
+		return command_usage(&log_writes_cmd);
+
+	if (mark_log(device, mark))
+		exitcode = 0;
+
+	return 0;
+}
+
+void
+log_writes_init(void)
+{
+	log_writes_cmd.name = "log_writes";
+	log_writes_cmd.altname = "lw";
+	log_writes_cmd.cfunc = log_writes_f;
+	log_writes_cmd.flags = CMD_NOMAP_OK | CMD_NOFILE_OK | CMD_FOREIGN_OK
+				| CMD_FLAG_ONESHOT;
+	log_writes_cmd.argmin = 0;
+	log_writes_cmd.argmax = -1;
+	log_writes_cmd.args = _("-d device -m mark");
+	log_writes_cmd.oneline =
+		_("create mark <mark> in the dm-log-writes log specified by <device>");
+
+	add_command(&log_writes_cmd);
+}
diff --git a/m4/Makefile b/m4/Makefile
index 4706121b..77f2edda 100644
--- a/m4/Makefile
+++ b/m4/Makefile
@@ -15,6 +15,7 @@ CONFIGURE = \
 LSRCFILES = \
 	manual_format.m4 \
 	package_blkid.m4 \
+	package_devmapper.m4 \
 	package_globals.m4 \
 	package_libcdev.m4 \
 	package_pthread.m4 \
diff --git a/m4/package_devmapper.m4 b/m4/package_devmapper.m4
new file mode 100644
index 00000000..821f283c
--- /dev/null
+++ b/m4/package_devmapper.m4
@@ -0,0 +1,11 @@
+#
+# See if libdevmapper is available on the system.
+#
+AC_DEFUN([AC_HAVE_DEVMAPPER],
+[ AC_SEARCH_LIBS([dm_task_create], [devmapper],
+        libdevmapper="-ldevmapper"
+        have_devmapper=yes,
+        have_devmapper=no,)
+    AC_SUBST(have_devmapper)
+    AC_SUBST(libdevmapper)
+])
diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
index 1693f7f1..4fce6d39 100644
--- a/man/man8/xfs_io.8
+++ b/man/man8/xfs_io.8
@@ -1123,7 +1123,27 @@ version of policy structure (numeric)
 .BR get_encpolicy
 On filesystems that support encryption, display the encryption policy of the
 current file.
+.RE
+.PD
+.TP
+.BI "log_writes \-d " device " \-m "  mark
+Create a mark named
+.I mark
+in the dm-log-writes log specified by
+.I device.
+This is intended to be equivalent to the shell command:
 
+.B dmsetup message
+.I device
+.B 0 mark
+.I mark
+.PD
+.RE
+.TP
+.B lw
+See the
+.B log_writes
+command.
 .SH SEE ALSO
 .BR mkfs.xfs (8),
 .BR xfsctl (3),
@@ -1141,4 +1161,5 @@ current file.
 .BR open (2),
 .BR pread (2),
 .BR pwrite (2),
-.BR readdir (3).
+.BR readdir (3),
+.BR dmsetup (8).
-- 
2.14.3