Add mirror log fault-handling policy.

WHATS_NEW

@@ -1,5 +1,7 @@
 Version 2.02.06 -
 =================================
+  Add mirror log fault-handling policy.
+  Improve mirror warning messages and tidy dmeventd syslog output.
   Propagate nosync flag around cluster.
   Allow vgreduce to handle mirror log failures.
   Add --corelog to lvcreate and lvconvert.

daemons/dmeventd/plugins/mirror/dmeventd_mirror.c

@@ -99,10 +99,13 @@ static int _get_mirror_event(char *params)
 	return rtn;
 }
 
-static void _temporary_log_fn(int level, const char *file, int line, const char *format)
+static void _temporary_log_fn(int level, const char *file,
+			      int line, const char *format)
 {
-	return;
+	if (!strncmp(format, "WARNING: ", 9) && (level < 5))
-	syslog(LOG_DEBUG, "%s", format);
+		syslog(LOG_CRIT, "%s", format);
+	else
+		syslog(LOG_DEBUG, "%s", format);
 }
 
 static int _remove_failed_devices(const char *device)
@@ -205,7 +208,7 @@ void process_event(const char *device, enum dm_event_type event)
 
 int register_device(const char *device)
 {
-	syslog(LOG_INFO, "Monitoring %s for events\n", device);
+	syslog(LOG_INFO, "Monitoring mirror device, %s for events\n", device);
 
 	/*
 	 * Need some space for allocations.  1024 should be more
@@ -224,8 +227,6 @@ int register_device(const char *device)
 
 int unregister_device(const char *device)
 {
-        syslog(LOG_INFO, "Stopped monitoring %s for events\n", device);
-
 	if (!(--register_count)) {
 		dm_pool_destroy(mem_pool);
 		mem_pool = NULL;

dmeventd/mirror/dmeventd_mirror.c

@@ -99,10 +99,13 @@ static int _get_mirror_event(char *params)
 	return rtn;
 }
 
-static void _temporary_log_fn(int level, const char *file, int line, const char *format)
+static void _temporary_log_fn(int level, const char *file,
+			      int line, const char *format)
 {
-	return;
+	if (!strncmp(format, "WARNING: ", 9) && (level < 5))
-	syslog(LOG_DEBUG, "%s", format);
+		syslog(LOG_CRIT, "%s", format);
+	else
+		syslog(LOG_DEBUG, "%s", format);
 }
 
 static int _remove_failed_devices(const char *device)
@@ -205,7 +208,7 @@ void process_event(const char *device, enum dm_event_type event)
 
 int register_device(const char *device)
 {
-	syslog(LOG_INFO, "Monitoring %s for events\n", device);
+	syslog(LOG_INFO, "Monitoring mirror device, %s for events\n", device);
 
 	/*
 	 * Need some space for allocations.  1024 should be more
@@ -224,8 +227,6 @@ int register_device(const char *device)
 
 int unregister_device(const char *device)
 {
-        syslog(LOG_INFO, "Stopped monitoring %s for events\n", device);
-
 	if (!(--register_count)) {
 		dm_pool_destroy(mem_pool);
 		mem_pool = NULL;

doc/example.conf

@@ -232,9 +232,6 @@ activation {
     # target or make it return zeros.
     missing_stripe_filler = "/dev/ioerror"
 
-    # Size (in KB) of each copy operation when mirroring
-    mirror_region_size = 512
-
     # How much stack (in KB) to reserve for use while devices suspended
     reserved_stack = 256
 
@@ -251,6 +248,54 @@ activation {
     #   "@*" matches if any tag defined on the host is also set in the LV or VG
     #
     # volume_list = [ "vg1", "vg2/lvol1", "@tag1", "@*" ]
+
+    # Size (in KB) of each copy operation when mirroring
+    mirror_region_size = 512
+
+    # 'mirror_image_fault_policy' and 'mirror_log_fault_policy' define
+    # how a device failure affecting a mirror is handled.
+    # A mirror is composed of mirror images (copies) and a log.
+    # A disk log ensures that a mirror does not need to be re-synced
+    # (all copies made the same) every time a machine reboots or crashes.
+    #
+    # In the event of a failure, the specified policy will be used to
+    # determine what happens:
+    #
+    # "remove" - Simply remove the faulty device and run without it.  If
+    #            the log device fails, the mirror would convert to using
+    #            an in-memory log.  This means the mirror will not
+    #            remember its sync status across crashes/reboots and
+    #            the entire mirror will be re-synced.  If a
+    #            mirror image fails, the mirror will convert to a
+    #            non-mirrored device if there is only one remaining good
+    #            copy.
+    #
+    # "allocate" - Remove the faulty device and try to allocate space on
+    #            a new device to be a replacement for the failed device.
+    #            Using this policy for the log is fast and maintains the
+    #            ability to remember sync state through crashes/reboots.
+    #            Using this policy for a mirror device is slow, as it
+    #            requires the mirror to resynchronize the devices, but it
+    #            will preserve the mirror characteristic of the device.
+    #            This policy acts like "remove" if no suitable device and
+    #            space can be allocated for the replacement.
+    #            Currently this is not implemented properly and behaves
+    #            similarly to:
+    #
+    # "allocate_anywhere" - Operates like "allocate", but it does not
+    #            require that the new space being allocated be on a
+    #            device is not part of the mirror.  For a log device
+    #            failure, this could mean that the log is allocated on
+    #            the same device as a mirror device.  For a mirror
+    #            device, this could mean that the mirror device is
+    #            allocated on the same device as another mirror device.
+    #            This policy would not be wise for mirror devices
+    #            because it would break the redundant nature of the
+    #            mirror.  This policy acts like "remove" if no suitable
+    #            device and space can be allocated for the replacement.
+
+    mirror_log_fault_policy = "allocate"
+    mirror_dev_fault_policy = "remove"
 }
 
 

lib/config/defaults.h

@@ -34,6 +34,8 @@
 #define DEFAULT_LOCK_DIR "/var/lock/lvm"
 #define DEFAULT_LOCKING_LIB "lvm2_locking.so"
 
+#define DEFAULT_MIRROR_LOG_FAULT_POLICY "allocate"
+#define DEFAULT_MIRROR_DEV_FAULT_POLICY "remove"
 #define DEFAULT_DMEVENTD_MIRROR_LIB "libdevmapper-event-lvm2mirror.so"
 
 #define DEFAULT_UMASK 0077

lib/metadata/mirror.c

@@ -23,6 +23,13 @@
 #include "lvm-string.h"
 #include "locking.h"	/* FIXME Should not be used in this file */
 
+#include "defaults.h" /* FIXME: should this be defaults.h? */
+
+/* These are the flags that represent the mirror failure restoration policies */
+#define MIRROR_REMOVE            0
+#define MIRROR_ALLOCATE          1
+#define MIRROR_ALLOCATE_ANYWHERE 2
+
 struct lv_segment *find_mirror_seg(struct lv_segment *seg)
 {
 	return seg->mirror_seg;
@@ -230,18 +237,112 @@ int remove_mirror_images(struct lv_segment *mirrored_seg, uint32_t num_mirrors,
 	return 1;
 }
 
+static int get_mirror_fault_policy(struct cmd_context *cmd, int log_policy)
+{
+	const char *policy;
+
+	if (log_policy)
+		policy = find_config_str(NULL, "activation/mirror_log_fault_policy",
+					 DEFAULT_MIRROR_LOG_FAULT_POLICY);
+	else
+		policy = find_config_str(NULL, "activation/mirror_dev_fault_policy",
+					 DEFAULT_MIRROR_DEV_FAULT_POLICY);
+
+	if (!strcmp(policy, "remove"))
+		return MIRROR_REMOVE;
+	else if (!strcmp(policy, "allocate"))
+		return MIRROR_ALLOCATE;
+	else if (!strcmp(policy, "allocate_anywhere"))
+		return MIRROR_ALLOCATE_ANYWHERE;
+
+	if (log_policy)
+		log_error("Bad activation/mirror_log_fault_policy");
+	else
+		log_error("Bad activation/mirror_dev_fault_policy");
+
+	return MIRROR_REMOVE;
+}
+
+static int get_mirror_log_fault_policy(struct cmd_context *cmd)
+{
+	return get_mirror_fault_policy(cmd, 1);
+}
+
+static int get_mirror_dev_fault_policy(struct cmd_context *cmd)
+{
+	return get_mirror_fault_policy(cmd, 0);
+}
+
+/*
+ * replace_mirror_images
+ * @mirrored_seg: segment (which may be linear now) to restore
+ * @num_mirrors: number of copies we should end up with
+ * @replace_log: replace log if not present
+ * @in_sync: was the original mirror in-sync?
+ *
+ * in_sync will be set to 0 if new mirror devices are being added
+ * In other words, it is only useful if the log (and only the log)
+ * is being restored.
+ *
+ * Returns: 0 on failure, 1 on reconfig, -1 if no reconfig done
+ */
+static int replace_mirror_images(struct lv_segment *mirrored_seg,
+				 uint32_t num_mirrors,
+				 int log_policy, int in_sync)
+{
+	int r = -1;
+	struct logical_volume *lv = mirrored_seg->lv;
+
+	/* FIXME: Use lvconvert rather than duplicating its code */
+
+	if (mirrored_seg->area_count < num_mirrors) {
+		log_error("WARNING: Failed to replace mirror device in %s/%s",
+			  mirrored_seg->lv->vg->name, mirrored_seg->lv->name);
+
+		if ((mirrored_seg->area_count > 1) && !mirrored_seg->log_lv)
+			log_error("WARNING: Use 'lvconvert -m %d %s/%s --corelog' to replace failed devices",
+				  num_mirrors - 1, lv->vg->name, lv->name);
+		else
+			log_error("WARNING: Use 'lvconvert -m %d %s/%s' to replace failed devices",
+				  num_mirrors - 1, lv->vg->name, lv->name);
+		r = 0;
+
+		/* REMEMBER/FIXME: set in_sync to 0 if a new mirror device was added */
+		in_sync = 0;
+	}
+
+	/*
+	 * FIXME: right now, we ignore the allocation policy specified to
+	 * allocate the new log.
+	 */
+	if ((mirrored_seg->area_count > 1) && !mirrored_seg->log_lv &&
+	    (log_policy != MIRROR_REMOVE)) {
+		log_error("WARNING: Failed to replace mirror log device in %s/%s",
+			  lv->vg->name, lv->name);
+
+		log_error("WARNING: Use 'lvconvert -m %d %s/%s' to replace failed devices",
+			  mirrored_seg->area_count - 1 , lv->vg->name, lv->name);
+		r = 0;
+	}
+
+	return r;
+}
+
 int reconfigure_mirror_images(struct lv_segment *mirrored_seg, uint32_t num_mirrors,
 			      struct list *removable_pvs, int remove_log)
 {
 	int r;
 	int insync = 0;
-	// int mirror_dev_failed = (mirrored_seg->area_count != num_mirrors);
+	int log_policy, dev_policy;
+	uint32_t old_num_mirrors = mirrored_seg->area_count;
+	int had_log = (mirrored_seg->log_lv) ? 1 : 0;
 	float sync_percent = 0;
 
 	/* was the mirror in-sync before problems? */
 	if (!lv_mirror_percent(mirrored_seg->lv->vg->cmd,
 			       mirrored_seg->lv, 0, &sync_percent, NULL))
-		log_error("Unable to determine mirror sync status.");
+		log_error("WARNING: Unable to determine mirror sync status of %s/%s.",
+			  mirrored_seg->lv->vg->name, mirrored_seg->lv->name);
 	else if (sync_percent >= 100.0)
 		insync = 1;
 
@@ -258,6 +359,38 @@ int reconfigure_mirror_images(struct lv_segment *mirrored_seg, uint32_t num_mirr
 		/* Unable to remove bad devices */
 		return 0;
 
+	log_print("WARNING: Bad device removed from mirror volume, %s/%s",
+		  mirrored_seg->lv->vg->name, mirrored_seg->lv->name);
+
+	log_policy = get_mirror_log_fault_policy(mirrored_seg->lv->vg->cmd);
+	dev_policy = get_mirror_dev_fault_policy(mirrored_seg->lv->vg->cmd);
+
+	r = replace_mirror_images(mirrored_seg,
+				  (dev_policy != MIRROR_REMOVE) ?
+				  old_num_mirrors : num_mirrors,
+				  log_policy, insync);
+
+	if (!r)
+		/* Failed to replace device(s) */
+		log_error("WARNING: Unable to find substitute device for mirror volume, %s/%s",
+			  mirrored_seg->lv->vg->name, mirrored_seg->lv->name);
+	else if (r > 0)
+		/* Success in replacing device(s) */
+		log_print("WARNING: Mirror volume, %s/%s restored - substitute for failed device found.",
+			  mirrored_seg->lv->vg->name, mirrored_seg->lv->name);
+	else
+		/* Bad device removed, but not replaced because of policy */
+		if (mirrored_seg->area_count == 1) {
+			log_print("WARNING: Mirror volume, %s/%s converted to linear due to device failure.",
+				  mirrored_seg->lv->vg->name, mirrored_seg->lv->name);
+		} else if (had_log && !mirrored_seg->log_lv) {
+			log_print("WARNING: Mirror volume, %s/%s disk log removed due to device failure.",
+				  mirrored_seg->lv->vg->name, mirrored_seg->lv->name);
+		}
+	/*
+	 * If we made it here, we at least removed the bad device.
+	 * Consider this success.
+	 */
 	return 1;
 }