Add a [--poll {y|n}] flag to vgchange and lvchange to control whether

the background polldaemon is allowed to start.  It can be used
standalone or in conjunction with --refresh or --available y.

Control over when the background polldaemon starts will be particularly
important for snapshot-merge of a root filesystem.

Dracut will be updated to activate all LVs with: --poll n

The lvm2-monitor initscript will start polling with: --poll y

NOTE: Because we currently have no way of knowing if a background
polldaemon is active for a given LV the following limitations exist and
have been deemed acceptable:
1) it is not possible to stop an active polldaemon; so the lvm2-monitor
   initscript doesn't stop running polldaemon(s)
2) redundant polldaemon instances will be started for all specified LVs
   if vgchange or lvchange are repeatedly used with '--poll y'

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

4 files changed, 99 insertions, 11 deletions

diff --git a/tools/args.h b/tools/args.h
index 1f2427b6..85f6a3cf 100644
--- a/tools/args.h
+++ b/tools/args.h
@@ -64,6 +64,7 @@ arg(dataalignmentoffset_ARG, '\0', "dataalignmentoffset", size_kb_arg, 0)
 arg(virtualoriginsize_ARG, '\0', "virtualoriginsize", size_mb_arg, 0)
 arg(virtualsize_ARG, '\0', "virtualsize", size_mb_arg, 0)
 arg(noudevsync_ARG, '\0', "noudevsync", NULL, 0)
+arg(poll_ARG, '\0', "poll", yes_no_arg, 0)
 
 /* Allow some variations */
 arg(resizable_ARG, '\0', "resizable", yes_no_arg, 0)
diff --git a/tools/commands.h b/tools/commands.h
index 85222e4e..032bde64 100644
--- a/tools/commands.h
+++ b/tools/commands.h
@@ -72,6 +72,7 @@ xx(lvchange,
    "\t[--ignorelockingfailure]\n"
    "\t[--ignoremonitoring]\n"
    "\t[--monitor {y|n}]\n"
+   "\t[--poll {y|n}]\n"
    "\t[--noudevsync]\n"
    "\t[-M|--persistent y|n] [--major major] [--minor minor]\n"
    "\t[-P|--partial] " "\n"
@@ -88,8 +89,8 @@ xx(lvchange,
    alloc_ARG, autobackup_ARG, available_ARG, contiguous_ARG, force_ARG,
    ignorelockingfailure_ARG, ignoremonitoring_ARG, major_ARG, minor_ARG,
    monitor_ARG, noudevsync_ARG, partial_ARG, permission_ARG, persistent_ARG,
-   readahead_ARG, resync_ARG, refresh_ARG, addtag_ARG, deltag_ARG, test_ARG,
-   yes_ARG)
+   poll_ARG, readahead_ARG, resync_ARG, refresh_ARG, addtag_ARG, deltag_ARG,
+   test_ARG, yes_ARG)
 
 xx(lvconvert,
    "Change logical volume layout",
@@ -688,6 +689,7 @@ xx(vgchange,
    "\t[--ignorelockingfailure]\n"
    "\t[--ignoremonitoring]\n"
    "\t[--monitor {y|n}]\n"
+   "\t[--poll {y|n}]\n"
    "\t[--noudevsync]\n"
    "\t[--refresh]\n"
    "\t[-t|--test]" "\n"
@@ -707,7 +709,7 @@ xx(vgchange,
    addtag_ARG, alloc_ARG, allocation_ARG, autobackup_ARG, available_ARG,
    clustered_ARG, deltag_ARG, ignorelockingfailure_ARG, ignoremonitoring_ARG,
    logicalvolume_ARG, maxphysicalvolumes_ARG, monitor_ARG, noudevsync_ARG,
-   partial_ARG, physicalextentsize_ARG, refresh_ARG, resizeable_ARG,
+   partial_ARG, physicalextentsize_ARG, poll_ARG, refresh_ARG, resizeable_ARG,
    resizable_ARG, test_ARG, uuid_ARG)
 
 xx(vgck,
diff --git a/tools/lvchange.c b/tools/lvchange.c
index f43b07af..f01d560a 100644
--- a/tools/lvchange.c
+++ b/tools/lvchange.c
@@ -101,6 +101,22 @@ static int lvchange_monitoring(struct cmd_context *cmd,
 	return 1;
 }
 
+static int lvchange_background_polling(struct cmd_context *cmd,
+				       struct logical_volume *lv)
+{
+	struct lvinfo info;
+
+	if (!lv_info(cmd, lv, &info, 0, 0) || !info.exists) {
+		log_error("Logical volume, %s, is not active", lv->name);
+		return 0;
+	}
+
+	if (background_polling())
+		lv_spawn_background_polling(cmd, lv);
+
+	return 1;
+}
+
 static int lvchange_availability(struct cmd_context *cmd,
 				 struct logical_volume *lv)
 {
@@ -135,7 +151,8 @@ static int lvchange_availability(struct cmd_context *cmd,
 				return_0;
 		}
 
-		lv_spawn_background_polling(cmd, lv);
+		if (background_polling())
+			lv_spawn_background_polling(cmd, lv);
 	}
 
 	return 1;
@@ -577,6 +594,9 @@ static int lvchange_single(struct cmd_context *cmd, struct logical_volume *lv,
 					    (is_static() || arg_count(cmd, ignoremonitoring_ARG)) ?
 					    DMEVENTD_MONITOR_IGNORE : DEFAULT_DMEVENTD_MONITOR));
 
+	init_background_polling(arg_int_value(cmd, poll_ARG,
+					      DEFAULT_BACKGROUND_POLLING));
+
 	/* access permission change */
 	if (arg_count(cmd, permission_ARG)) {
 		if (!archive(lv->vg)) {
@@ -679,6 +699,15 @@ static int lvchange_single(struct cmd_context *cmd, struct logical_volume *lv,
 		}
 	}
 
+	if (!arg_count(cmd, available_ARG) &&
+	    !arg_count(cmd, refresh_ARG) &&
+	    arg_count(cmd, poll_ARG)) {
+		if (!lvchange_background_polling(cmd, lv)) {
+			stack;
+			return ECMD_FAILED;
+		}
+	}
+
 	if (doit != docmds) {
 		stack;
 		return ECMD_FAILED;
@@ -695,10 +724,10 @@ int lvchange(struct cmd_context *cmd, int argc, char **argv)
 	    && !arg_count(cmd, persistent_ARG) && !arg_count(cmd, addtag_ARG)
 	    && !arg_count(cmd, deltag_ARG) && !arg_count(cmd, refresh_ARG)
 	    && !arg_count(cmd, alloc_ARG) && !arg_count(cmd, monitor_ARG)
-	    && !arg_count(cmd, resync_ARG)) {
+	    && !arg_count(cmd, poll_ARG) && !arg_count(cmd, resync_ARG)) {
 		log_error("Need 1 or more of -a, -C, -j, -m, -M, -p, -r, "
-			  "--resync, --refresh, --alloc, --addtag, --deltag "
-			  "or --monitor");
+			  "--resync, --refresh, --alloc, --addtag, --deltag, "
+			  "--monitor or --poll");
 		return EINVALID_CMD_LINE;
 	}
 
diff --git a/tools/vgchange.c b/tools/vgchange.c
index 1c52e75f..9b6b27ff 100644
--- a/tools/vgchange.c
+++ b/tools/vgchange.c
@@ -51,6 +51,39 @@ static int _monitor_lvs_in_vg(struct cmd_context *cmd,
 	return count;
 }
 
+static int _poll_lvs_in_vg(struct cmd_context *cmd,
+			   struct volume_group *vg)
+{
+	struct lv_list *lvl;
+	struct logical_volume *lv;
+	struct lvinfo info;
+	int lv_active;
+	int count = 0;
+
+	dm_list_iterate_items(lvl, &vg->lvs) {
+		lv = lvl->lv;
+
+		if (!lv_info(cmd, lv, &info, 0, 0))
+			lv_active = 0;
+		else
+			lv_active = info.exists;
+
+		if (!lv_active ||
+		    !(lv->status & (PVMOVE|CONVERTING)))
+			continue;
+
+		lv_spawn_background_polling(cmd, lv);
+		count++;
+	}
+
+	/*
+	 * returns the number of polled devices
+	 * - there is no way to know if lv is already being polled
+	 */
+
+	return count;
+}
+
 static int _activate_lvs_in_vg(struct cmd_context *cmd,
 			       struct volume_group *vg, int activate)
 {
@@ -95,7 +128,8 @@ static int _activate_lvs_in_vg(struct cmd_context *cmd,
 		} else if (!activate_lv(cmd, lv))
 			continue;
 
-		if (activate != CHANGE_AN && activate != CHANGE_ALN &&
+		if (background_polling() &&
+		    activate != CHANGE_AN && activate != CHANGE_ALN &&
 		    (lv->status & (PVMOVE|CONVERTING)))
 			lv_spawn_background_polling(cmd, lv);
 
@@ -125,6 +159,20 @@ static int _vgchange_monitoring(struct cmd_context *cmd, struct volume_group *vg
 	return ECMD_PROCESSED;
 }
 
+static int _vgchange_background_polling(struct cmd_context *cmd, struct volume_group *vg)
+{
+	int polled;
+
+	if (lvs_in_vg_activated(vg) && background_polling()) {
+	        polled = _poll_lvs_in_vg(cmd, vg);
+		log_print("Background polling started for %d logical volume(s) "
+			  "in volume group \"%s\"",
+			  polled, vg->name);
+	}
+
+	return ECMD_PROCESSED;
+}
+
 static int _vgchange_available(struct cmd_context *cmd, struct volume_group *vg)
 {
 	int lv_open, active, monitored;
@@ -490,12 +538,18 @@ static int vgchange_single(struct cmd_context *cmd, const char *vg_name,
 					    (is_static() || arg_count(cmd, ignoremonitoring_ARG)) ?
 					    DMEVENTD_MONITOR_IGNORE : DEFAULT_DMEVENTD_MONITOR));
 
+	init_background_polling(arg_int_value(cmd, poll_ARG,
+					      DEFAULT_BACKGROUND_POLLING));
+
 	if (arg_count(cmd, available_ARG))
 		r = _vgchange_available(cmd, vg);
 
 	else if (arg_count(cmd, monitor_ARG))
 		r = _vgchange_monitoring(cmd, vg);
 
+	else if (arg_count(cmd, poll_ARG))
+		r = _vgchange_background_polling(cmd, vg);
+
 	else if (arg_count(cmd, resizeable_ARG))
 		r = _vgchange_resizeable(cmd, vg);
 
@@ -538,9 +592,11 @@ int vgchange(struct cmd_context *cmd, int argc, char **argv)
 	     arg_count(cmd, addtag_ARG) + arg_count(cmd, uuid_ARG) +
 	     arg_count(cmd, physicalextentsize_ARG) +
 	     arg_count(cmd, clustered_ARG) + arg_count(cmd, alloc_ARG) +
-	     arg_count(cmd, monitor_ARG) + arg_count(cmd, refresh_ARG))) {
-		log_error("One of -a, -c, -l, -p, -s, -x, --refresh, "
-				"--uuid, --alloc, --addtag or --deltag required");
+	     arg_count(cmd, monitor_ARG) + arg_count(cmd, poll_ARG) +
+	     arg_count(cmd, refresh_ARG))) {
+		log_error("Need 1 or more of -a, -c, -l, -p, -s, -x, "
+			  "--refresh, --uuid, --alloc, --addtag, --deltag, "
+			  "--monitor or --poll");
 		return EINVALID_CMD_LINE;
 	}