[PATCH 1/2] kexec: implement -y (--no-sync) option

[Tejun Heo]

>From a32a35e46a950cd0e4b4e317a9062c41e79fbfeb Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj at kernel.org>
Date: Thu, 26 Mar 2015 14:56:26 -0400

During kernel develoment, kexec can be used to get out of sticky
situations without going through possibly lenghty reboot; however,
there are situations where the filesystem and/or storage stack are
known to be misbehaving and performing sync before kexecing is
dangerous or just never finishes.

This patch implement -y (--no-sync) option which makes kexec skip
syncing in the similar way as -x (--no-ifdown).

Signed-off-by: Tejun Heo <tj at kernel.org>
Suggested-by: Chris Mason <clm at fb.com>
---
 kexec/kexec.8 | 8 ++++++--
 kexec/kexec.c | 8 +++++++-
 kexec/kexec.h | 4 +++-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/kexec/kexec.8 b/kexec/kexec.8
index 2575f9e..24d1969 100644
--- a/kexec/kexec.8
+++ b/kexec/kexec.8
@@ -6,7 +6,7 @@
 kexec \- directly boot into a new kernel
 .SH SYNOPSIS
 .B /sbin/kexec
-.B [-v (\-\-version)] [-f (\-\-force)] [-x (\-\-no-ifdown)] [-l (\-\-load)] [-p (\-\-load-panic)] [-u (\-\-unload)] [-e (\-\-exec)] [-t (\-\-type)]
+.B [-v (\-\-version)] [-f (\-\-force)] [-x (\-\-no-ifdown)] [-y (\-\-no-sync)] [-l (\-\-load)] [-p (\-\-load-panic)] [-u (\-\-unload)] [-e (\-\-exec)] [-t (\-\-type)]
 .BI [\-\-mem\-min= addr ]
 .BI [\-\-mem\-max= addr ]
 
@@ -148,7 +148,11 @@ Return the version number of the installed utility.
 .TP
 .B \-x\ (\-\-no\-ifdown)
 Shut down the running kernel, but restore the interface on reload. (If
-this option is used, it must be specified last.)
+this option is used, it must be one of last options specified.)
+.TP
+.B \-y\ (\-\-no\-sync)
+Shut down the running kernel, but skip syncing the filesystems. (If
+this option is used, it must be one of last options specified.)
 .TP
 .BI \-\-mem\-min= addr
 Specify the lowest memory address
diff --git a/kexec/kexec.c b/kexec/kexec.c
index b088916..7123460 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -913,7 +913,10 @@ void usage(void)
 	       " -f, --force          Force an immediate kexec,\n"
 	       "                      don't call shutdown.\n"
 	       " -x, --no-ifdown      Don't bring down network interfaces.\n"
-	       "                      (if used, must be last option\n"
+	       "                      (if used, must be one of last options\n"
+	       "                       specified)\n"
+	       " -y, --no-sync        Don't sync filesystems before kexec.\n"
+	       "                      (if used, must be one of last options\n"
 	       "                       specified)\n"
 	       " -l, --load           Load the new kernel into the\n"
 	       "                      current kernel.\n"
@@ -1218,6 +1221,9 @@ int main(int argc, char *argv[])
 		case OPT_NOIFDOWN:
 			do_ifdown = 0;
 			break;
+		case OPT_NOSYNC:
+			do_sync = 0;
+			break;
 		case OPT_FORCE:
 			do_load = 1;
 			do_shutdown = 0;
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 4be2b2f..b129c15 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -209,6 +209,7 @@ extern int file_types;
 #define OPT_DEBUG		'd'
 #define OPT_FORCE		'f'
 #define OPT_NOIFDOWN		'x'
+#define OPT_NOSYNC		'y'
 #define OPT_EXEC		'e'
 #define OPT_LOAD		'l'
 #define OPT_UNLOAD		'u'
@@ -227,6 +228,7 @@ extern int file_types;
 	{ "version",		0, 0, OPT_VERSION }, \
 	{ "force",		0, 0, OPT_FORCE }, \
 	{ "no-ifdown",		0, 0, OPT_NOIFDOWN }, \
+	{ "no-sync",		0, 0, OPT_NOSYNC }, \
 	{ "load",		0, 0, OPT_LOAD }, \
 	{ "unload",		0, 0, OPT_UNLOAD }, \
 	{ "exec",		0, 0, OPT_EXEC }, \
@@ -241,7 +243,7 @@ extern int file_types;
 	{ "kexec-file-syscall",	0, 0, OPT_KEXEC_FILE_SYSCALL }, \
 	{ "debug",		0, 0, OPT_DEBUG }, \
 
-#define KEXEC_OPT_STR "h?vdfxluet:ps"
+#define KEXEC_OPT_STR "h?vdfxyluet:ps"
 
 extern void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr);
 extern void die(const char *fmt, ...)
-- 
2.1.0