Kernels 4.3 and newer (commit 1bab0de0 "dm-mpath, scsi_dh: don't
let dm detach device handlers") imply "retain_attached_hw_handler yes".
Clarify this in the propsel code, log messages, and documentation.
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
---
libmultipath/configure.c | 3 ++-
libmultipath/dmparser.c | 3 ++-
libmultipath/propsel.c | 7 ++++++-
libmultipath/util.c | 36 ++++++++++++++++++++++++++++++++++++
libmultipath/util.h | 2 ++
multipath/multipath.conf.5 | 15 +++++++++++----
6 files changed, 59 insertions(+), 7 deletions(-)
diff --git a/libmultipath/configure.c b/libmultipath/configure.c
index a7f2b443..74b6f52a 100644
--- a/libmultipath/configure.c
+++ b/libmultipath/configure.c
@@ -572,7 +572,8 @@ select_action (struct multipath * mpp, vector curmp, int force_reload)
}
if (mpp->retain_hwhandler != RETAIN_HWHANDLER_UNDEF &&
- mpp->retain_hwhandler != cmpp->retain_hwhandler) {
+ mpp->retain_hwhandler != cmpp->retain_hwhandler &&
+ get_linux_version_code() < KERNEL_VERSION(4, 3, 0)) {
mpp->action = ACT_RELOAD;
condlog(3, "%s: set ACT_RELOAD (retain_hwhandler change)",
mpp->alias);
diff --git a/libmultipath/dmparser.c b/libmultipath/dmparser.c
index 1121c715..b647c256 100644
--- a/libmultipath/dmparser.c
+++ b/libmultipath/dmparser.c
@@ -97,7 +97,8 @@ assemble_map (struct multipath * mp, char * params, int len)
} else if (mp->no_path_retry != NO_PATH_RETRY_UNDEF) {
add_feature(&f, no_path_retry);
}
- if (mp->retain_hwhandler == RETAIN_HWHANDLER_ON)
+ if (mp->retain_hwhandler == RETAIN_HWHANDLER_ON &&
+ get_linux_version_code() < KERNEL_VERSION(4, 3, 0))
add_feature(&f, retain_hwhandler);
APPEND(p, end, "%s %s %i %i", f, mp->hwhandler, nr_priority_groups,
diff --git a/libmultipath/propsel.c b/libmultipath/propsel.c
index e885a845..d609394e 100644
--- a/libmultipath/propsel.c
+++ b/libmultipath/propsel.c
@@ -628,7 +628,12 @@ int select_retain_hwhandler(struct config *conf, struct multipath *mp)
if (!VERSION_GE(conf->version, minv_dm_retain)) {
mp->retain_hwhandler = RETAIN_HWHANDLER_OFF;
- origin = "(setting: WARNING, requires kernel version >= 1.5.0)";
+ origin = "(setting: WARNING, requires kernel dm-mpath version >= 1.5.0)";
+ goto out;
+ }
+ if (get_linux_version_code() >= KERNEL_VERSION(4, 3, 0)) {
+ mp->retain_hwhandler = RETAIN_HWHANDLER_ON;
+ origin = "(setting: implied in kernel >= 4.3.0)";
goto out;
}
mp_set_ovr(retain_hwhandler);
diff --git a/libmultipath/util.c b/libmultipath/util.c
index b90cd8b0..dff2ed3c 100644
--- a/libmultipath/util.c
+++ b/libmultipath/util.c
@@ -6,6 +6,7 @@
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <sys/types.h>
+#include <sys/utsname.h>
#include <dirent.h>
#include <unistd.h>
#include <errno.h>
@@ -380,3 +381,38 @@ int systemd_service_enabled(const char *dev)
found = systemd_service_enabled_in(dev, "/run");
return found;
}
+
+static int _linux_version_code;
+static pthread_once_t _lvc_initialized = PTHREAD_ONCE_INIT;
+
+/* Returns current kernel version encoded as major*65536 + minor*256 + patch,
+ * so, for example, to check if the kernel is greater than 2.2.11:
+ *
+ * if (get_linux_version_code() > KERNEL_VERSION(2,2,11)) { <stuff> }
+ *
+ * Copyright (C) 1999-2004 by Erik Andersen <andersen@xxxxxxxxxxxx>
+ * Code copied from busybox (GPLv2 or later)
+ */
+static void
+_set_linux_version_code(void)
+{
+ struct utsname name;
+ char *t;
+ int i, r;
+
+ uname(&name); /* never fails */
+ t = name.release;
+ r = 0;
+ for (i = 0; i < 3; i++) {
+ t = strtok(t, ".");
+ r = r * 256 + (t ? atoi(t) : 0);
+ t = NULL;
+ }
+ _linux_version_code = r;
+}
+
+int get_linux_version_code(void)
+{
+ pthread_once(&_lvc_initialized, _set_linux_version_code);
+ return _linux_version_code;
+}
diff --git a/libmultipath/util.h b/libmultipath/util.h
index b087e32e..45291be8 100644
--- a/libmultipath/util.h
+++ b/libmultipath/util.h
@@ -15,6 +15,8 @@ char *convert_dev(char *dev, int is_path_device);
char *parse_uid_attribute_by_attrs(char *uid_attrs, char *path_dev);
void setup_thread_attr(pthread_attr_t *attr, size_t stacksize, int detached);
int systemd_service_enabled(const char *dev);
+int get_linux_version_code(void);
+#define KERNEL_VERSION(maj, min, ptc) ((((maj) * 256) + (min)) * 256 + (ptc))
#define safe_sprintf(var, format, args...) \
snprintf(var, sizeof(var), format, ##args) >= sizeof(var)
diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
index b32d0383..3b4e5187 100644
--- a/multipath/multipath.conf.5
+++ b/multipath/multipath.conf.5
@@ -698,15 +698,16 @@ The default is: \fB<unset>\fR
.
.TP
.B retain_attached_hw_handler
-If set to
+(Obsolete for kernels >= 4.3) If set to
.I yes
and the SCSI layer has already attached a hardware_handler to the device,
multipath will not force the device to use the hardware_handler specified by
mutipath.conf. If the SCSI layer has not attached a hardware handler,
multipath will continue to use its configured hardware handler.
.RS
-.TP
-The default is: \fByes\fR
+.PP
+The default is: \fByes\fR. Linux kernel 4.3 or newer always behaves as if
+\fB"retain_attached_hw_handler yes"\fR was set.
.RE
.
.
@@ -1182,8 +1183,14 @@ Active/Standby mode exclusively.
.I 1 alua
(Hardware-dependent)
Hardware handler for SCSI-3 ALUA compatible arrays.
-.TP
+.PP
The default is: \fB<unset>\fR
+.PP
+\fBImportant Note:\fR Linux kernels 4.3 and newer automatically attach a device
+handler to known devices (which includes all devices supporting SCSI-3 ALUA)
+and disallow changing the handler
+afterwards. Setting \fBhardware_handler\fR for such devices on these kernels
+has no effect.
.RE
.
.
--
2.13.1
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