v1.6 Release

Finish the release notes for the 1.6 release.

Signed-off-by: Zach Brown <zab@versity.com>

ReleaseNotes.md

@@ -1,6 +1,22 @@
 Versity ScoutFS Release Notes
 =============================
 
+---
+v1.6
+\
+*Jul 7, 2022*
+
+* **Fix memory leaks in rare corner cases**
+\
+  Analysis tools found a few corner cases that leaked small structures,
+  generally around error handling or startup and shutdown.
+
+* **Add --skip-likely-huge scoutfs print command option**
+\
+  Add an option to scoutfs print to reduce the size of the output
+  so that it can be used to see system-wide metadata without being
+  overwhelmed by file-level details.
+
 ---
 v1.5
 \

kmod/src/net.c

@@ -355,6 +355,7 @@ static int submit_send(struct super_block *sb,
 		}
 		if (rid != 0) {
 			spin_unlock(&conn->lock);
+			kfree(msend);
 			return -ENOTCONN;
 		}
 	}
@@ -1345,10 +1346,12 @@ scoutfs_net_alloc_conn(struct super_block *sb,
 	if (!conn)
 		return NULL;
 
-	conn->info = kzalloc(info_size, GFP_NOFS);
-	if (!conn->info) {
-		kfree(conn);
-		return NULL;
+	if (info_size) {
+		conn->info = kzalloc(info_size, GFP_NOFS);
+		if (!conn->info) {
+			kfree(conn);
+			return NULL;
+		}
 	}
 
 	conn->workq = alloc_workqueue("scoutfs_net_%s",

kmod/src/omap.c

@@ -157,6 +157,15 @@ static int free_rid(struct omap_rid_list *list, struct omap_rid_entry *entry)
 	return nr;
 }
 
+static void free_rid_list(struct omap_rid_list *list)
+{
+	struct omap_rid_entry *entry;
+	struct omap_rid_entry *tmp;
+
+	list_for_each_entry_safe(entry, tmp, &list->head, head)
+		free_rid(list, entry);
+}
+
 static int copy_rids(struct omap_rid_list *to, struct omap_rid_list *from, spinlock_t *from_lock)
 {
 	struct omap_rid_entry *entry;
@@ -804,6 +813,10 @@ void scoutfs_omap_server_shutdown(struct super_block *sb)
 	llist_for_each_entry_safe(req, tmp, requests, llnode)
 		kfree(req);
 
+	spin_lock(&ominf->lock);
+	free_rid_list(&ominf->rids);
+	spin_unlock(&ominf->lock);
+
 	synchronize_rcu();
 }
 
@@ -864,6 +877,10 @@ void scoutfs_omap_destroy(struct super_block *sb)
 		rhashtable_walk_stop(&iter);
 		rhashtable_walk_exit(&iter);
 
+		spin_lock(&ominf->lock);
+		free_rid_list(&ominf->rids);
+		spin_unlock(&ominf->lock);
+
 		rhashtable_destroy(&ominf->group_ht);
 		rhashtable_destroy(&ominf->req_ht);
 		kfree(ominf);

kmod/src/super.c

@@ -496,7 +496,7 @@ static int scoutfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	ret = assign_random_id(sbi);
 	if (ret < 0)
-		return ret;
+		goto out;
 
 	spin_lock_init(&sbi->next_ino_lock);
 	spin_lock_init(&sbi->data_wait_root.lock);
@@ -505,7 +505,7 @@ static int scoutfs_fill_super(struct super_block *sb, void *data, int silent)
 	/* parse options early for use during setup */
 	ret = scoutfs_options_early_setup(sb, data);
 	if (ret < 0)
-		return ret;
+		goto out;
 	scoutfs_options_read(sb, &opts);
 
 	ret = sb_set_blocksize(sb, SCOUTFS_BLOCK_SM_SIZE);

utils/fenced/ipmi-remote-host

@@ -1,140 +0,0 @@
-#!/usr/bin/bash
-# /usr/libexec/scoutfs-fenced/run/ipmi-remote-host
-
-# ipmi configuration
-SCOUTFS_IPMI_CONFIG_FILE=${SCOUTFS_IPMI_CONFIG_FILE:-/etc/scoutfs/scoutfs-ipmi.conf}
-SCOUTFS_IPMI_HOSTS_FILE=${SCOUTFS_IPMI_HOSTS_FILE:-/etc/scoutfs/scoutfs-ipmi-hosts.conf}
-
-## hosts file format
-## SCOUTFS_HOST_IP IPMI_ADDRESS
-## ex:
-#  192.168.1.1     192.168.10.1
-
-# command setup
-IPMI_POWER="/sbin/ipmipower"
-SSH_CMD="ssh -o ConnectTimeout=3 -o BatchMode=yes -o StrictHostKeyChecking=no"
-LOGGER="/bin/logger -p local3.crit -t scoutfs-fenced"
-
-$LOGGER "ipmi fence script invoked: IP: $SCOUTFS_FENCED_REQ_IP RID: $SCOUTFS_FENCED_REQ_RID TEST: $IPMITEST"
-
-echo_fail() {
-    echo "$@" >&2
-    $LOGGER "fence failed: $@"
-    exit 1
-}
-
-echo_log() {
-    echo "$@" >&2
-    $LOGGER "fence info: $@"
-}
-
-echo_test_pass() {
-    echo -e "\xE2\x9C\x94 $@"
-}
-
-echo_test_fail() {
-    echo -e "\xE2\x9D\x8C $@"
-}
-
-test -n "$SCOUTFS_IPMI_CONFIG_FILE" || \
-    echo_fail "SCOUTFS_IPMI_CONFIG_FILE isn't set"
-test -r "$SCOUTFS_IPMI_CONFIG_FILE" || \
-    echo_fail "$SCOUTFS_IPMI_CONFIG_FILE isn't readable file"
-. "$SCOUTFS_IPMI_CONFIG_FILE"
-test -n "$SCOUTFS_IPMI_HOSTS_FILE" || \
-    echo_fail "SCOUTFS_IPMI_HOSTS_FILE isn't set"
-test -r "$SCOUTFS_IPMI_HOSTS_FILE" || \
-    echo_fail "$SCOUTFS_IPMI_HOSTS_FILE isn't readable file"
-test -x "$IPMI_POWER" || \
-    echo_fail "$IPMI_POWER not found, need to install freeimpi?"
-
-export ip="$SCOUTFS_FENCED_REQ_IP"
-export rid="$SCOUTFS_FENCED_REQ_RID"
-
-getIPMIhost () {
-    host=$(awk -v ip="$1" '$1 == ip {print $2}' "$SCOUTFS_IPMI_HOSTS_FILE") || \
-        echo_fail "lookup ipmi host failed"
-    echo "$host"
-}
-
-powerOffHost() {
-    # older versions of ipmipower inverted wait-until-off/wait-until-on, so specify both
-    $IPMI_POWER $IPMI_OPTS -h "$1" --wait-until-off --wait-until-on --off || \
-        echo_fail "ipmi power off $1 failed"
-
-    ipmioutput=$($IPMI_POWER $IPMI_OPTS -h "$1" --stat) || \
-        echo_fail "ipmi power stat $1 failed"
-
-    if [[ ! "$ipmioutput" =~ off ]]; then
-        echo_fail "ipmi stat $1 not off"
-    fi
-
-    $LOGGER "ipmi fence power down $1 success"
-
-    exit 0
-}
-
-if [ -n "$IPMITEST" ]; then
-    for i in $(awk '!/^($|[[:space:]]*#)/ {print $1}' "$SCOUTFS_IPMI_HOSTS_FILE"); do
-        if ! $SSH_CMD "$i" /bin/true; then
-            echo_test_fail "ssh $i"
-        else
-            echo_test_pass "ssh $i"
-        fi
-	host=$(getIPMIhost "$i")
-        if [ -z "$host" ]; then
-            echo_test_fail "ipmi config $i $host"
-        else
-            if ! $IPMI_POWER $IPMI_OPTS -h "$host" --stat; then
-                echo_test_fail "ipmi $i"
-            else
-                echo_test_pass "ipmi $i"
-            fi
-        fi
-    done
-    exit 0
-fi
-
-if [ -z "$ip" ]; then
-    echo_fail "no IP given for fencing"
-fi
-
-host=$(getIPMIhost "$ip")
-if [ -z "$host" ]; then
-    echo_fail "no IPMI host found for fence IP"
-fi
-
-# first check via ssh if the mount still exists
-# if ssh succeeds, we will only power down the node if mounted
-if ! output=$($SSH_CMD "$ip" "echo BEGIN; LC_ALL=C egrep -m 1 '(^0x*|^$rid$)' /sys/kernel/boot_params/version /sys/fs/scoutfs/f*r*/rid; echo END"); then
-    # ssh not working, just power down host
-    powerOffHost "$host"
-fi
-
-if [[ ! "$output" =~ BEGIN ]]; then
-    # ssh failure
-    echo_log "no BEGIN"
-    powerOffHost "$host"
-fi
-
-if [[ ! "$output" =~ \/boot_params\/ ]]; then
-    # ssh failure
-    echo_log "no boot params"
-    powerOffHost "$host"
-fi
-
-if [[ ! "$output" =~ END ]]; then
-    # ssh failure
-    echo_log "no END"
-    powerOffHost "$host"
-fi
-
-if [[ "$output" =~ "rid:$rid" ]]; then
-    # rid still mounted, power down
-    echo_log "rid $rid still mounted"
-    powerOffHost "$host"
-fi
-
-$LOGGER "ipmi fence host $ip/$host success (rid $rid not mounted)"
-exit 0
-

utils/fenced/local-force-unmount

@@ -1,36 +0,0 @@
-#!/usr/bin/bash
-# /usr/libexec/scoutfs-fenced/run/local-force-umount
-
-echo_fail() {
-	echo "$@" > /dev/stderr
-	exit 1
-}
-
-rid="$SCOUTFS_FENCED_REQ_RID"
-
-#
-# Look for a local mount with the rid to fence.  Typically we'll at
-# least find the mount with the server that requested the fence that
-# we're processing.   But it's possible that mounts are unmounted
-# before, or while, we're running.
-#
-mnts=$(findmnt -l -n -t scoutfs -o TARGET) || \
-	echo_fail "findmnt -t scoutfs failed" > /dev/stderr
-
-for mnt in $mnts; do
-	mnt_rid=$(scoutfs statfs -p "$mnt" -s rid) || \
-		echo_fail "scoutfs statfs $mnt failed"
-
-	if [ "$mnt_rid" == "$rid" ]; then
-		umount -f "$mnt" || \
-			echo_fail "umout -f $mnt"
-
-		exit 0
-	fi
-done
-
-#
-# If the mount doesn't exist on this host then it can't access the
-# devices by definition and can be considered fenced.
-#
-exit 0

utils/fenced/powerman-remote-host

@@ -1,139 +0,0 @@
-#!/usr/bin/bash
-# /usr/libexec/scoutfs-fenced/run/powerman-remote-host
-
-# powerman configuration
-SCOUTFS_PM_CONFIG_FILE=${SCOUTFS_PM_CONFIG_FILE:-/etc/scoutfs/scoutfs-pm.conf}
-SCOUTFS_PM_HOSTS_FILE=${SCOUTFS_PM_HOSTS_FILE:-/etc/scoutfs/scoutfs-pm-hosts.conf}
-
-## hosts file format
-## SCOUTFS_HOST_IP POWERMAN_NODE_NAME
-## ex:
-#  192.168.1.1     dm1
-
-# command setup
-PM_CMD="/usr/bin/pm"
-SSH_CMD="ssh -o ConnectTimeout=3 -o BatchMode=yes -o StrictHostKeyChecking=no"
-LOGGER="/bin/logger -p local3.crit -t scoutfs-fenced"
-
-$LOGGER "ipmi fence script invoked: IP: $SCOUTFS_FENCED_REQ_IP RID: $SCOUTFS_FENCED_REQ_RID TEST: $IPMITEST"
-
-echo_fail() {
-    echo "$@" >&2
-    $LOGGER "fence failed: $@"
-    exit 1
-}
-
-echo_log() {
-    echo "$@" >&2
-    $LOGGER "fence info: $@"
-}
-
-echo_test_pass() {
-    echo -e "\xE2\x9C\x94 $@"
-}
-
-echo_test_fail() {
-    echo -e "\xE2\x9D\x8C $@"
-}
-
-test -n "$SCOUTFS_PM_CONFIG_FILE" || \
-    echo_fail "SCOUTFS_PM_CONFIG_FILE isn't set"
-test -r "$SCOUTFS_PM_CONFIG_FILE" || \
-    echo_fail "$SCOUTFS_PM_CONFIG_FILE isn't readable file"
-. "$SCOUTFS_PM_CONFIG_FILE"
-test -n "$SCOUTFS_PM_HOSTS_FILE" || \
-    echo_fail "SCOUTFS_PM_HOSTS_FILE isn't set"
-test -r "$SCOUTFS_PM_HOSTS_FILE" || \
-    echo_fail "$SCOUTFS_PM_HOSTS_FILE isn't readable file"
-test -x "$PM_CMD" || \
-    echo_fail "$PMCMD not found, need to install powerman?"
-
-export ip="$SCOUTFS_FENCED_REQ_IP"
-fence_rid="$SCOUTFS_FENCED_REQ_RID"
-
-getPMhost () {
-    host=$(awk -v ip="$1" '$1 == ip {print $2}' "$SCOUTFS_PM_HOSTS_FILE") || \
-        echo_fail "lookup pm host failed"
-    echo "$host"
-}
-
-powerOffHost() {
-    $PM_CMD $PM_OPTS "$1" -0 || \
-        echo_fail "pm power off $host failed"
-
-    pmoutput=$($PM_CMD $PM_OPTS "$1" -q | grep "$1") || \
-        echo_fail "powerman power stat $1 failed"
-
-    if [[ ! "$pmoutput" =~ off ]]; then
-        echo_fail "powerman stat $1 not off"
-    fi
-
-    $LOGGER "powerman fence power down $1 success"
-
-    exit 0
-}
-
-if [ -n "$PMTEST" ]; then
-    for i in $(awk '!/^($|[[:space:]]*#)/ {print $1}' "$SCOUTFS_PM_HOSTS_FILE"); do
-        if ! $SSH_CMD "$i" /bin/true; then
-            echo_test_fail "ssh $i"
-        else
-            echo_test_pass "ssh $i"
-        fi
-	host=$(getPMhost "$i")
-        if [ -z "$host" ]; then
-            echo_test_fail "pm config $i $host"
-        else
-            if ! $PM_CMD $PM_OPTS "$host" -q; then
-                echo_test_fail "pm $i"
-            else
-                echo_test_pass "pm $i"
-            fi
-        fi
-    done
-    exit 0
-fi
-
-if [ -z "$ip" ]; then
-    echo_fail "no IP given for fencing"
-fi
-
-host=$(getPMhost "$ip")
-if [ -z "$host" ]; then
-    echo_fail "no host found for fence IP"
-fi
-
-# first check via ssh if the mount still exists
-# if ssh succeeds, we will only power down the node if mounted
-if ! output=$($SSH_CMD "$ip" "echo BEGIN; LC_ALL=C egrep -m 1 '(^0x*|^$rid$)' /sys/kernel/boot_params/version /sys/fs/scoutfs/f*r*/rid; echo END"); then
-    # ssh not working, just power down host
-    powerOffHost "$host"
-fi
-
-if [[ ! "$output" =~ BEGIN ]]; then
-    # ssh failure
-    echo_log "no BEGIN"
-    powerOffHost "$host"
-fi
-
-if [[ ! "$output" =~ \/boot_params\/ ]]; then
-    # ssh failure
-    echo_log "no boot params"
-    powerOffHost "$host"
-fi
-
-if [[ ! "$output" =~ END ]]; then
-    # ssh failure
-    echo_log "no END"
-    powerOffHost "$host"
-fi
-
-if [[ "$output" =~ "rid:$rid" ]]; then
-    # rid still mounted, power down
-    echo_log "rid $rid still mounted"
-    powerOffHost "$host"
-fi
-
-$LOGGER "powerman fence host $ip/$host success (rid $rid not mounted)"
-exit 0
-

utils/fenced/scoutfs-ipmi-hosts.conf

@@ -1,11 +0,0 @@
-# /etc/scoutfs/scoutfs-ipmi-hosts.conf
-
-## config file format
-##
-## SCOUTFS_HOST_IP must match the interface used for scoutfs
-## leader/follower communications
-##
-## SCOUTFS_HOST_IP IPMI_ADDRESS
-## ex:
-#192.168.1.1     192.168.10.1
-

utils/fenced/scoutfs-ipmi.conf

@@ -1,10 +0,0 @@
-#!/usr/bin/bash
-# /etc/scoutfs/scoutfs-ipmi.conf
-
-IPMI_USER="admin"
-IPMI_PASSWORD="password"
-IPMI_OPTS="-D LAN_2_0 -u $IPMI_USER -p $IPMI_PASSWORD"
-
-# some Intel BMCs need -I 17
-# IPMI_OPTS="-D LAN_2_0 -u $IPMI_USER -p $IPMI_PASSWORD -I 17"
-

utils/fenced/scoutfs-pm-hosts.conf

@@ -1,11 +0,0 @@
-# /etc/scoutfs/scoutfs-ipmi-hosts.conf
-
-## config file format
-##
-## SCOUTFS_HOST_IP must match the interface used for scoutfs
-## leader/follower communications
-##
-## SCOUTFS_HOST_IP POWERMAN_NODE_NAME
-## ex:
-#192.168.1.1     node1
-

utils/fenced/scoutfs-pm.conf

@@ -1,8 +0,0 @@
-#!/usr/bin/bash
-# /etc/scoutfs/scoutfs-pm.conf
-
-PM_OPTS=""
-
-# optionally specify remote powerman server
-#PM_OPTS="-h pm-server.localdomain"
-

utils/man/scoutfs.8

@@ -597,7 +597,7 @@ format.
 .PD
 
 .TP
-.BI "print META-DEVICE"
+.BI "print {-S|--skip-likely-huge} META-DEVICE"
 .sp
 Prints out all of the metadata in the file system.  This makes no effort
 to ensure that the structures are consistent as they're traversed and
@@ -607,6 +607,20 @@ output.
 .PD 0
 .TP
 .sp
+.B "-S, --skip-likely-huge"
+Skip printing structures that are likely to be very large.  The
+structures that are skipped tend to be global and whose size tends to be
+related to the size of the volume.   Examples of skipped structures include
+the global fs items, srch files, and metadata and data
+allocators.  Similar structures that are not skipped are related to the
+number of mounts and are maintained at a relatively reasonable size.
+These include per-mount log trees, srch files, allocators, and the
+metadata allocators used by server commits.
+.sp
+Skipping the larger structures limits the print output to a relatively
+constant size rather than being a large multiple of the used metadata
+space of the volume making the output much more useful for inspection.
+.TP
 .B "META-DEVICE"
 The path to the metadata device for the filesystem whose metadata will be
 printed.  Since this command reads via the host's buffer cache, it may not

utils/scoutfs-utils.spec.in

@@ -55,21 +55,14 @@ install -m 755 -D src/scoutfs $RPM_BUILD_ROOT%{_sbindir}/scoutfs
 install -m 644 -D src/ioctl.h $RPM_BUILD_ROOT%{_includedir}/scoutfs/ioctl.h
 install -m 644 -D src/format.h $RPM_BUILD_ROOT%{_includedir}/scoutfs/format.h
 install -m 755 -D fenced/scoutfs-fenced $RPM_BUILD_ROOT%{_libexecdir}/scoutfs-fenced/scoutfs-fenced
-install -m 755 -D fenced/local-force-unmount $RPM_BUILD_ROOT%{_libexecdir}/scoutfs-fenced/run/local-force-unmount
-install -m 755 -D fenced/ipmi-remote-host $RPM_BUILD_ROOT%{_libexecdir}/scoutfs-fenced/run/ipmi-remote-host
-install -m 755 -D fenced/powerman-remote-host $RPM_BUILD_ROOT%{_libexecdir}/scoutfs-fenced/run/powerman-remote-host
 install -m 644 -D fenced/scoutfs-fenced.service $RPM_BUILD_ROOT%{_unitdir}/scoutfs-fenced.service
 install -m 644 -D fenced/scoutfs-fenced.conf.example $RPM_BUILD_ROOT%{_sysconfdir}/scoutfs/scoutfs-fenced.conf.example
-install -m 644 -D fenced/scoutfs-ipmi.conf $RPM_BUILD_ROOT%{_sysconfdir}/scoutfs/scoutfs-ipmi.conf
-install -m 644 -D fenced/scoutfs-ipmi-hosts.conf $RPM_BUILD_ROOT%{_sysconfdir}/scoutfs/scoutfs-ipmi-hosts.conf
-install -m 644 -D fenced/scoutfs-pm.conf $RPM_BUILD_ROOT%{_sysconfdir}/scoutfs/scoutfs-pm.conf
-install -m 644 -D fenced/scoutfs-pm-hosts.conf $RPM_BUILD_ROOT%{_sysconfdir}/scoutfs/scoutfs-pm-hosts.conf
 
 %files
 %defattr(644,root,root,755)
 %{_mandir}/man*/scoutfs*.gz
 %{_unitdir}/scoutfs-fenced.service
-%config(noreplace) %{_sysconfdir}/scoutfs
+%{_sysconfdir}/scoutfs
 %defattr(755,root,root,755)
 %{_sbindir}/scoutfs
 %{_libexecdir}/scoutfs-fenced

utils/src/print.c

@@ -8,6 +8,7 @@
 #include <errno.h>
 #include <string.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <ctype.h>
 #include <uuid/uuid.h>
 #include <sys/socket.h>
@@ -989,9 +990,10 @@ static void print_super_block(struct scoutfs_super_block *super, u64 blkno)
 
 struct print_args {
 	char *meta_device;
+	bool skip_likely_huge;
 };
 
-static int print_volume(int fd)
+static int print_volume(int fd, struct print_args *args)
 {
 	struct scoutfs_super_block *super = NULL;
 	struct print_recursion_args pa;
@@ -1041,23 +1043,26 @@ static int print_volume(int fd)
 			ret = err;
 	}
 
-	for (i = 0; i < array_size(super->meta_alloc); i++) {
-		snprintf(str, sizeof(str), "meta_alloc[%u]", i);
-		err = print_btree(fd, super, str, &super->meta_alloc[i].root,
+	if (!args->skip_likely_huge) {
+		for (i = 0; i < array_size(super->meta_alloc); i++) {
+			snprintf(str, sizeof(str), "meta_alloc[%u]", i);
+			err = print_btree(fd, super, str, &super->meta_alloc[i].root,
+					  print_alloc_item, NULL);
+			if (err && !ret)
+				ret = err;
+		}
+
+		err = print_btree(fd, super, "data_alloc", &super->data_alloc.root,
 				  print_alloc_item, NULL);
 		if (err && !ret)
 			ret = err;
 	}
 
-	err = print_btree(fd, super, "data_alloc", &super->data_alloc.root,
-			  print_alloc_item, NULL);
-	if (err && !ret)
-		ret = err;
-
 	err = print_btree(fd, super, "srch_root", &super->srch_root,
 			  print_srch_root_item, NULL);
 	if (err && !ret)
 		ret = err;
+
 	err = print_btree(fd, super, "logs_root", &super->logs_root,
 			  print_log_trees_item, NULL);
 	if (err && !ret)
@@ -1065,19 +1070,23 @@ static int print_volume(int fd)
 
 	pa.super = super;
 	pa.fd = fd;
-	err = print_btree_leaf_items(fd, super, &super->srch_root.ref,
-				     print_srch_root_files, &pa);
-	if (err && !ret)
-		ret = err;
+	if (!args->skip_likely_huge) {
+		err = print_btree_leaf_items(fd, super, &super->srch_root.ref,
+					     print_srch_root_files, &pa);
+		if (err && !ret)
+			ret = err;
+	}
 	err = print_btree_leaf_items(fd, super, &super->logs_root.ref,
 				     print_log_trees_roots, &pa);
 	if (err && !ret)
 		ret = err;
 
-	err = print_btree(fd, super, "fs_root", &super->fs_root,
-			  print_fs_item, NULL);
-	if (err && !ret)
-		ret = err;
+	if (!args->skip_likely_huge) {
+		err = print_btree(fd, super, "fs_root", &super->fs_root,
+				  print_fs_item, NULL);
+		if (err && !ret)
+			ret = err;
+	}
 
 out:
 	free(super);
@@ -1098,7 +1107,7 @@ static int do_print(struct print_args *args)
 		return ret;
 	}
 
-	ret = print_volume(fd);
+	ret = print_volume(fd, args);
 	close(fd);
 	return ret;
 };
@@ -1108,6 +1117,9 @@ static int parse_opt(int key, char *arg, struct argp_state *state)
 	struct print_args *args = state->input;
 
 	switch (key) {
+	case 'S':
+		args->skip_likely_huge = true;
+		break;
 	case ARGP_KEY_ARG:
 		if (!args->meta_device)
 			args->meta_device = strdup_or_error(state, arg);
@@ -1125,8 +1137,13 @@ static int parse_opt(int key, char *arg, struct argp_state *state)
 	return 0;
 }
 
+static struct argp_option options[] = {
+	{ "skip-likely-huge", 'S', NULL, 0, "Skip large structures to minimize output size"},
+	{ NULL }
+};
+
 static struct argp argp = {
-	NULL,
+	options,
 	parse_opt,
 	"META-DEV",
 	"Print metadata structures"