From 6e60b28bc979477ba8d48347dd556acc5296bb25 Mon Sep 17 00:00:00 2001
From: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Date: Tue, 19 Apr 2022 15:58:46 +0100
Subject: [PATCH 1/3] Revert "etc/systemd/zfs-mount-generator: serialise,
 handle keylocation=http[s]://"

This reverts commit fe6f2651f55de3bf68ac4729386b5e85aa23a447.

This is to continue support for ubuntu specific zsys patch that
currently relies on the shell based implementation of the
generator. See https://bugs.launchpad.net/bugs/1958142

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
---
 .../system-generators/zfs-mount-generator.c   | 437 +++++++++++-------
 man/man8/zfs-mount-generator.8.in             |  19 +-
 2 files changed, 275 insertions(+), 181 deletions(-)

diff --git a/etc/systemd/system-generators/zfs-mount-generator.c b/etc/systemd/system-generators/zfs-mount-generator.c
index f4c6c26a0b..b806339deb 100644
--- a/etc/systemd/system-generators/zfs-mount-generator.c
+++ b/etc/systemd/system-generators/zfs-mount-generator.c
@@ -27,6 +27,9 @@
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
+#include <sys/mman.h>
+#include <semaphore.h>
 #include <stdbool.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -41,16 +44,25 @@
 #include <errno.h>
 #include <libzfs.h>
 
-/*
- * For debugging only.
- *
- * Free statics with trivial life-times,
- * but saved line filenames are replaced with a static string.
- */
-#define	FREE_STATICS false
-
-#define	nitems(arr) (sizeof (arr) / sizeof (*arr))
 #define	STRCMP ((int(*)(const void *, const void *))&strcmp)
+#define	PID_T_CMP ((int(*)(const void *, const void *))&pid_t_cmp)
+
+static int
+pid_t_cmp(const pid_t *lhs, const pid_t *rhs)
+{
+	/*
+	 * This is always valid, quoth sys_types.h(7posix):
+	 * > blksize_t, pid_t, and ssize_t shall be signed integer types.
+	 */
+	return (*lhs - *rhs);
+}
+
+#define	EXIT_ENOMEM() \
+	do { \
+		fprintf(stderr, PROGNAME "[%d]: " \
+		    "not enough memory (L%d)!\n", getpid(), __LINE__); \
+		_exit(1); \
+	} while (0)
 
 
 #define	PROGNAME "zfs-mount-generator"
@@ -68,11 +80,20 @@
 #define	URI_REGEX_S "^\\([A-Za-z][A-Za-z0-9+.\\-]*\\):\\/\\/\\(.*\\)$"
 static regex_t uri_regex;
 
+static char *argv0;
+
 static const char *destdir = "/tmp";
 static int destdir_fd = -1;
 
 static void *known_pools = NULL; /* tsearch() of C strings */
-static void *noauto_files = NULL; /* tsearch() of C strings */
+static struct {
+	sem_t noauto_not_on_sem;
+
+	sem_t noauto_names_sem;
+	size_t noauto_names_len;
+	size_t noauto_names_max;
+	char noauto_names[][NAME_MAX];
+} *noauto_files;
 
 
 static char *
@@ -82,12 +103,8 @@ systemd_escape(const char *input, const char *prepend, const char *append)
 	size_t applen = strlen(append);
 	size_t prelen = strlen(prepend);
 	char *ret = malloc(4 * len + prelen + applen + 1);
-	if (!ret) {
-		fprintf(stderr, PROGNAME "[%d]: "
-		    "out of memory to escape \"%s%s%s\"!\n",
-		    getpid(), prepend, input, append);
-		return (NULL);
-	}
+	if (!ret)
+		EXIT_ENOMEM();
 
 	memcpy(ret, prepend, prelen);
 	char *out = ret + prelen;
@@ -149,12 +166,8 @@ systemd_escape_path(char *input, const char *prepend, const char *append)
 {
 	if (strcmp(input, "/") == 0) {
 		char *ret;
-		if (asprintf(&ret, "%s-%s", prepend, append) == -1) {
-			fprintf(stderr, PROGNAME "[%d]: "
-			    "out of memory to escape \"%s%s%s\"!\n",
-			    getpid(), prepend, input, append);
-			ret = NULL;
-		}
+		if (asprintf(&ret, "%s-%s", prepend, append) == -1)
+			EXIT_ENOMEM();
 		return (ret);
 	} else {
 		/*
@@ -196,10 +209,6 @@ fopenat(int dirfd, const char *pathname, int flags,
 static int
 line_worker(char *line, const char *cachefile)
 {
-	int ret = 0;
-	void *tofree_all[8];
-	void **tofree = tofree_all;
-
 	char *toktmp;
 	/* BEGIN CSTYLED */
 	const char *dataset                     = strtok_r(line, "\t", &toktmp);
@@ -231,9 +240,11 @@ line_worker(char *line, const char *cachefile)
 	if (p_nbmand == NULL) {
 		fprintf(stderr, PROGNAME "[%d]: %s: not enough tokens!\n",
 		    getpid(), dataset);
-		goto err;
+		return (1);
 	}
 
+	strncpy(argv0, dataset, strlen(argv0));
+
 	/* Minimal pre-requisites to mount a ZFS dataset */
 	const char *after = "zfs-import.target";
 	const char *wants = "zfs-import.target";
@@ -269,31 +280,28 @@ line_worker(char *line, const char *cachefile)
 
 
 	if (strcmp(p_encroot, "-") != 0) {
-		char *keyloadunit = *(tofree++) =
+		char *keyloadunit =
 		    systemd_escape(p_encroot, "zfs-load-key@", ".service");
-		if (keyloadunit == NULL)
-			goto err;
 
 		if (strcmp(dataset, p_encroot) == 0) {
 			const char *keymountdep = NULL;
 			bool is_prompt = false;
-			bool need_network = false;
 
 			regmatch_t uri_matches[3];
 			if (regexec(&uri_regex, p_keyloc,
-			    nitems(uri_matches), uri_matches, 0) == 0) {
-				p_keyloc[uri_matches[1].rm_eo] = '\0';
+			    sizeof (uri_matches) / sizeof (*uri_matches),
+			    uri_matches, 0) == 0) {
 				p_keyloc[uri_matches[2].rm_eo] = '\0';
-				const char *scheme =
-				    &p_keyloc[uri_matches[1].rm_so];
 				const char *path =
 				    &p_keyloc[uri_matches[2].rm_so];
 
-				if (strcmp(scheme, "https") == 0 ||
-				    strcmp(scheme, "http") == 0)
-					need_network = true;
-				else
-					keymountdep = path;
+				/*
+				 * Assumes all URI keylocations need
+				 * the mount for their path;
+				 * http://, for example, wouldn't
+				 * (but it'd need network-online.target et al.)
+				 */
+				keymountdep = path;
 			} else {
 				if (strcmp(p_keyloc, "prompt") != 0)
 					fprintf(stderr, PROGNAME "[%d]: %s: "
@@ -313,7 +321,7 @@ line_worker(char *line, const char *cachefile)
 				    "couldn't open %s under %s: %s\n",
 				    getpid(), dataset, keyloadunit, destdir,
 				    strerror(errno));
-				goto err;
+				return (1);
 			}
 
 			fprintf(keyloadunit_f,
@@ -327,22 +335,20 @@ line_worker(char *line, const char *cachefile)
 			    "After=%s\n",
 			    dataset, cachefile, wants, after);
 
-			if (need_network)
-				fprintf(keyloadunit_f,
-				    "Wants=network-online.target\n"
-				    "After=network-online.target\n");
-
 			if (p_systemd_requires)
 				fprintf(keyloadunit_f,
 				    "Requires=%s\n", p_systemd_requires);
 
-			if (p_systemd_requiresmountsfor)
-				fprintf(keyloadunit_f,
-				    "RequiresMountsFor=%s\n",
-				    p_systemd_requiresmountsfor);
-			if (keymountdep)
-				fprintf(keyloadunit_f,
-				    "RequiresMountsFor='%s'\n", keymountdep);
+			if (p_systemd_requiresmountsfor || keymountdep) {
+				fprintf(keyloadunit_f, "RequiresMountsFor=");
+				if (p_systemd_requiresmountsfor)
+					fprintf(keyloadunit_f,
+					    "%s ", p_systemd_requiresmountsfor);
+				if (keymountdep)
+					fprintf(keyloadunit_f,
+					    "'%s'", keymountdep);
+				fprintf(keyloadunit_f, "\n");
+			}
 
 			/* BEGIN CSTYLED */
 			fprintf(keyloadunit_f,
@@ -387,13 +393,9 @@ line_worker(char *line, const char *cachefile)
 		if (after[0] == '\0')
 			after = keyloadunit;
 		else if (asprintf(&toktmp, "%s %s", after, keyloadunit) != -1)
-			after = *(tofree++) = toktmp;
-		else {
-			fprintf(stderr, PROGNAME "[%d]: %s: "
-			    "out of memory to generate after=\"%s %s\"!\n",
-			    getpid(), dataset, after, keyloadunit);
-			goto err;
-		}
+			after = toktmp;
+		else
+			EXIT_ENOMEM();
 	}
 
 
@@ -402,12 +404,12 @@ line_worker(char *line, const char *cachefile)
 	    strcmp(p_systemd_ignore, "off") == 0) {
 		/* ok */
 	} else if (strcmp(p_systemd_ignore, "on") == 0)
-		goto end;
+		return (0);
 	else {
 		fprintf(stderr, PROGNAME "[%d]: %s: "
 		    "invalid org.openzfs.systemd:ignore=%s\n",
 		    getpid(), dataset, p_systemd_ignore);
-		goto err;
+		return (1);
 	}
 
 	/* Check for canmount */
@@ -416,21 +418,21 @@ line_worker(char *line, const char *cachefile)
 	} else if (strcmp(p_canmount, "noauto") == 0)
 		noauto = true;
 	else if (strcmp(p_canmount, "off") == 0)
-		goto end;
+		return (0);
 	else {
 		fprintf(stderr, PROGNAME "[%d]: %s: invalid canmount=%s\n",
 		    getpid(), dataset, p_canmount);
-		goto err;
+		return (1);
 	}
 
 	/* Check for legacy and blank mountpoints */
 	if (strcmp(p_mountpoint, "legacy") == 0 ||
 	    strcmp(p_mountpoint, "none") == 0)
-		goto end;
+		return (0);
 	else if (p_mountpoint[0] != '/') {
 		fprintf(stderr, PROGNAME "[%d]: %s: invalid mountpoint=%s\n",
 		    getpid(), dataset, p_mountpoint);
-		goto err;
+		return (1);
 	}
 
 	/* Escape the mountpoint per systemd policy */
@@ -440,7 +442,7 @@ line_worker(char *line, const char *cachefile)
 		fprintf(stderr,
 		    PROGNAME "[%d]: %s: abnormal simplified mountpoint: %s\n",
 		    getpid(), dataset, p_mountpoint);
-		goto err;
+		return (1);
 	}
 
 
@@ -550,7 +552,8 @@ line_worker(char *line, const char *cachefile)
 	 * 	files if we're sure they were created by us. (see 5.)
 	 * 2.	We handle files differently based on canmount.
 	 * 	Units with canmount=on always have precedence over noauto.
-	 * 	This is enforced by processing these units before all others.
+	 * 	This is enforced by the noauto_not_on_sem semaphore,
+	 * 	which is only unlocked when the last canmount=on process exits.
 	 * 	It is important to use p_canmount and not noauto here,
 	 * 	since we categorise by canmount while other properties,
 	 * 	e.g. org.openzfs.systemd:wanted-by, also modify noauto.
@@ -558,7 +561,7 @@ line_worker(char *line, const char *cachefile)
 	 * 	Additionally, we use noauto_files to track the unit file names
 	 * 	(which are the systemd-escaped mountpoints) of all (exclusively)
 	 * 	noauto datasets that had a file created.
-	 * 4.	If the file to be created is found in the tracking tree,
+	 * 4.	If the file to be created is found in the tracking array,
 	 * 	we do NOT create it.
 	 * 5.	If a file exists for a noauto dataset,
 	 * 	we check whether the file name is in the array.
@@ -568,14 +571,29 @@ line_worker(char *line, const char *cachefile)
 	 * 	further noauto datasets creating a file for this path again.
 	 */
 
+	{
+		sem_t *our_sem = (strcmp(p_canmount, "on") == 0) ?
+		    &noauto_files->noauto_names_sem :
+		    &noauto_files->noauto_not_on_sem;
+		while (sem_wait(our_sem) == -1 && errno == EINTR)
+			;
+	}
+
 	struct stat stbuf;
 	bool already_exists = fstatat(destdir_fd, mountfile, &stbuf, 0) == 0;
-	bool is_known = tfind(mountfile, &noauto_files, STRCMP) != NULL;
 
-	*(tofree++) = (void *)mountfile;
+	bool is_known = false;
+	for (size_t i = 0; i < noauto_files->noauto_names_len; ++i) {
+		if (strncmp(
+		    noauto_files->noauto_names[i], mountfile, NAME_MAX) == 0) {
+			is_known = true;
+			break;
+		}
+	}
+
 	if (already_exists) {
 		if (is_known) {
-			/* If it's in noauto_files, we must be noauto too */
+			/* If it's in $noauto_files, we must be noauto too */
 
 			/* See 5 */
 			errno = 0;
@@ -596,31 +614,43 @@ line_worker(char *line, const char *cachefile)
 		}
 
 		/* File exists: skip current dataset */
-		goto end;
+		if (strcmp(p_canmount, "on") == 0)
+			sem_post(&noauto_files->noauto_names_sem);
+		return (0);
 	} else {
 		if (is_known) {
 			/* See 4 */
-			goto end;
+			if (strcmp(p_canmount, "on") == 0)
+				sem_post(&noauto_files->noauto_names_sem);
+			return (0);
 		} else if (strcmp(p_canmount, "noauto") == 0) {
-			if (tsearch(mountfile, &noauto_files, STRCMP) == NULL)
+			if (noauto_files->noauto_names_len ==
+			    noauto_files->noauto_names_max)
 				fprintf(stderr, PROGNAME "[%d]: %s: "
-				    "out of memory for noauto datasets! "
-				    "Not tracking %s.\n",
-				    getpid(), dataset, mountfile);
-			else
-				/* mountfile escaped to noauto_files */
-				*(--tofree) = NULL;
+				    "noauto dataset limit (%zu) reached! "
+				    "Not tracking %s. Please report this to "
+				    "https://github.com/openzfs/zfs\n",
+				    getpid(), dataset,
+				    noauto_files->noauto_names_max, mountfile);
+			else {
+				strncpy(noauto_files->noauto_names[
+				    noauto_files->noauto_names_len],
+				    mountfile, NAME_MAX);
+				++noauto_files->noauto_names_len;
+			}
 		}
 	}
 
 
 	FILE *mountfile_f = fopenat(destdir_fd, mountfile,
 	    O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, "w", 0644);
+	if (strcmp(p_canmount, "on") == 0)
+		sem_post(&noauto_files->noauto_names_sem);
 	if (!mountfile_f) {
 		fprintf(stderr,
 		    PROGNAME "[%d]: %s: couldn't open %s under %s: %s\n",
 		    getpid(), dataset, mountfile, destdir, strerror(errno));
-		goto err;
+		return (1);
 	}
 
 	fprintf(mountfile_f,
@@ -669,17 +699,12 @@ line_worker(char *line, const char *cachefile)
 	(void) fclose(mountfile_f);
 
 	if (!requiredby && !wantedby)
-		goto end;
+		return (0);
 
 	/* Finally, create the appropriate dependencies */
 	char *linktgt;
-	if (asprintf(&linktgt, "../%s", mountfile) == -1) {
-		fprintf(stderr, PROGNAME "[%d]: %s: "
-		    "out of memory for dependents of %s!\n",
-		    getpid(), dataset, mountfile);
-		goto err;
-	}
-	*(tofree++) = linktgt;
+	if (asprintf(&linktgt, "../%s", mountfile) == -1)
+		EXIT_ENOMEM();
 
 	char *dependencies[][2] = {
 		{"wants", wantedby},
@@ -694,14 +719,8 @@ line_worker(char *line, const char *cachefile)
 		    reqby;
 		    reqby = strtok_r(NULL, " ", &toktmp)) {
 			char *depdir;
-			if (asprintf(
-			    &depdir, "%s.%s", reqby, (*dep)[0]) == -1) {
-				fprintf(stderr, PROGNAME "[%d]: %s: "
-				    "out of memory for dependent dir name "
-				    "\"%s.%s\"!\n",
-				    getpid(), dataset, reqby, (*dep)[0]);
-				continue;
-			}
+			if (asprintf(&depdir, "%s.%s", reqby, (*dep)[0]) == -1)
+				EXIT_ENOMEM();
 
 			(void) mkdirat(destdir_fd, depdir, 0755);
 			int depdir_fd = openat(destdir_fd, depdir,
@@ -727,24 +746,7 @@ line_worker(char *line, const char *cachefile)
 		}
 	}
 
-end:
-	if (tofree >= tofree_all + nitems(tofree_all)) {
-		/*
-		 * This won't happen as-is:
-		 * we've got 8 slots and allocate 4 things at most.
-		 */
-		fprintf(stderr,
-		    PROGNAME "[%d]: %s: need to free %zu > %zu!\n",
-		    getpid(), dataset, tofree - tofree_all, nitems(tofree_all));
-		ret = tofree - tofree_all;
-	}
-
-	while (tofree-- != tofree_all)
-		free(*tofree);
-	return (ret);
-err:
-	ret = 1;
-	goto end;
+	return (0);
 }
 
 
@@ -778,11 +780,12 @@ main(int argc, char **argv)
 		if (kmfd >= 0) {
 			(void) dup2(kmfd, STDERR_FILENO);
 			(void) close(kmfd);
-
-			setlinebuf(stderr);
 		}
 	}
 
+	uint8_t debug = 0;
+
+	argv0 = argv[0];
 	switch (argc) {
 	case 1:
 		/* Use default */
@@ -841,9 +844,33 @@ main(int argc, char **argv)
 		}
 	}
 
-	bool debug = false;
+	{
+		/*
+		 * We could just get a gigabyte here and Not Care,
+		 * but if vm.overcommit_memory=2, then MAP_NORESERVE is ignored
+		 * and we'd try (and likely fail) to rip it out of swap
+		 */
+		noauto_files = mmap(NULL, 4 * 1024 * 1024,
+		    PROT_READ | PROT_WRITE,
+		    MAP_SHARED | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
+		if (noauto_files == MAP_FAILED) {
+			fprintf(stderr,
+			    PROGNAME "[%d]: couldn't allocate IPC region: %s\n",
+			    getpid(), strerror(errno));
+			_exit(1);
+		}
+
+		sem_init(&noauto_files->noauto_not_on_sem, true, 0);
+		sem_init(&noauto_files->noauto_names_sem, true, 1);
+		noauto_files->noauto_names_len = 0;
+		/* Works out to 16447ish, *well* enough */
+		noauto_files->noauto_names_max =
+		    (4 * 1024 * 1024 - sizeof (*noauto_files)) / NAME_MAX;
+	}
+
 	char *line = NULL;
 	size_t linelen = 0;
+	struct timespec time_start = {};
 	{
 		const char *dbgenv = getenv("ZFS_DEBUG");
 		if (dbgenv)
@@ -852,7 +879,7 @@ main(int argc, char **argv)
 			FILE *cmdline = fopen("/proc/cmdline", "re");
 			if (cmdline != NULL) {
 				if (getline(&line, &linelen, cmdline) >= 0)
-					debug = strstr(line, "debug");
+					debug = strstr(line, "debug") ? 2 : 0;
 				(void) fclose(cmdline);
 			}
 		}
@@ -861,17 +888,19 @@ main(int argc, char **argv)
 			dup2(STDERR_FILENO, STDOUT_FILENO);
 	}
 
-	struct timespec time_start = {};
+	size_t forked_canmount_on = 0;
+	size_t forked_canmount_not_on = 0;
+	size_t canmount_on_pids_len = 128;
+	pid_t *canmount_on_pids =
+	    malloc(canmount_on_pids_len * sizeof (*canmount_on_pids));
+	if (canmount_on_pids == NULL)
+		canmount_on_pids_len = 0;
+
 	if (debug)
 		clock_gettime(CLOCK_MONOTONIC_RAW, &time_start);
 
-	struct line {
-		char *line;
-		const char *fname;
-		struct line *next;
-	} *lines_canmount_not_on = NULL;
-
-	int ret = 0;
+	ssize_t read;
+	pid_t pid;
 	struct dirent *cachent;
 	while ((cachent = readdir(fslist_dir)) != NULL) {
 		if (strcmp(cachent->d_name, ".") == 0 ||
@@ -887,67 +916,129 @@ main(int argc, char **argv)
 			continue;
 		}
 
-		const char *filename = FREE_STATICS ? "(elided)" : NULL;
-
-		ssize_t read;
 		while ((read = getline(&line, &linelen, cachefile)) >= 0) {
 			line[read - 1] = '\0'; /* newline */
 
-			char *canmount = line;
-			canmount += strcspn(canmount, "\t");
-			canmount += strspn(canmount, "\t");
-			canmount += strcspn(canmount, "\t");
-			canmount += strspn(canmount, "\t");
-			bool canmount_on = strncmp(canmount, "on", 2) == 0;
-
-			if (canmount_on)
-				ret |= line_worker(line, cachent->d_name);
-			else {
-				if (filename == NULL)
-					filename =
-					    strdup(cachent->d_name) ?: "(?)";
-
-				struct line *l = calloc(1, sizeof (*l));
-				char *nl = strdup(line);
-				if (l == NULL || nl == NULL) {
-					fprintf(stderr, PROGNAME "[%d]: "
-					    "out of memory for \"%s\" in %s\n",
-					    getpid(), line, cachent->d_name);
-					free(l);
-					free(nl);
-					continue;
+			switch (pid = fork()) {
+			case -1:
+				fprintf(stderr,
+				    PROGNAME "[%d]: couldn't fork for %s: %s\n",
+				    getpid(), line, strerror(errno));
+				break;
+			case 0: /* child */
+				_exit(line_worker(line, cachent->d_name));
+			default: { /* parent */
+				char *tmp;
+				char *dset = strtok_r(line, "\t", &tmp);
+				strtok_r(NULL, "\t", &tmp);
+				char *canmount = strtok_r(NULL, "\t", &tmp);
+				bool canmount_on =
+				    canmount && strncmp(canmount, "on", 2) == 0;
+
+				if (debug >= 2)
+					printf(PROGNAME ": forked %d, "
+					    "canmount_on=%d, dataset=%s\n",
+					    (int)pid, canmount_on, dset);
+
+				if (canmount_on &&
+				    forked_canmount_on ==
+				    canmount_on_pids_len) {
+					size_t new_len =
+					    (canmount_on_pids_len ?: 16) * 2;
+					void *new_pidlist =
+					    realloc(canmount_on_pids,
+					    new_len *
+					    sizeof (*canmount_on_pids));
+					if (!new_pidlist) {
+						fprintf(stderr,
+						    PROGNAME "[%d]: "
+						    "out of memory! "
+						    "Mount ordering may be "
+						    "affected.\n", getpid());
+						continue;
+					}
+
+					canmount_on_pids = new_pidlist;
+					canmount_on_pids_len = new_len;
 				}
-				l->line = nl;
-				l->fname = filename;
-				l->next = lines_canmount_not_on;
-				lines_canmount_not_on = l;
+
+				if (canmount_on) {
+					canmount_on_pids[forked_canmount_on] =
+					    pid;
+					++forked_canmount_on;
+				} else
+					++forked_canmount_not_on;
+				break;
+			}
 			}
 		}
 
-		fclose(cachefile);
+		(void) fclose(cachefile);
 	}
 	free(line);
 
-	while (lines_canmount_not_on) {
-		struct line *l = lines_canmount_not_on;
-		lines_canmount_not_on = l->next;
+	if (forked_canmount_on == 0) {
+		/* No canmount=on processes to finish, so don't deadlock here */
+		for (size_t i = 0; i < forked_canmount_not_on; ++i)
+			sem_post(&noauto_files->noauto_not_on_sem);
+	} else {
+		/* Likely a no-op, since we got these from a narrow fork loop */
+		qsort(canmount_on_pids, forked_canmount_on,
+		    sizeof (*canmount_on_pids), PID_T_CMP);
+	}
 
-		ret |= line_worker(l->line, l->fname);
-		if (FREE_STATICS) {
-			free(l->line);
-			free(l);
+	int status, ret = 0;
+	struct rusage usage;
+	size_t forked_canmount_on_max = forked_canmount_on;
+	while ((pid = wait4(-1, &status, 0, &usage)) != -1) {
+		ret |= WEXITSTATUS(status) | WTERMSIG(status);
+
+		if (forked_canmount_on != 0) {
+			if (bsearch(&pid, canmount_on_pids,
+			    forked_canmount_on_max, sizeof (*canmount_on_pids),
+			    PID_T_CMP))
+				--forked_canmount_on;
+
+			if (forked_canmount_on == 0) {
+				/*
+				 * All canmount=on processes have finished,
+				 * let all the lower-priority ones finish now
+				 */
+				for (size_t i = 0;
+				    i < forked_canmount_not_on; ++i)
+					sem_post(
+					    &noauto_files->noauto_not_on_sem);
+			}
 		}
+
+		if (debug >= 2)
+			printf(PROGNAME ": %d done, user=%llu.%06us, "
+			    "system=%llu.%06us, maxrss=%ldB, ex=0x%x\n",
+			    (int)pid,
+			    (unsigned long long) usage.ru_utime.tv_sec,
+			    (unsigned int) usage.ru_utime.tv_usec,
+			    (unsigned long long) usage.ru_stime.tv_sec,
+			    (unsigned int) usage.ru_stime.tv_usec,
+			    usage.ru_maxrss * 1024, status);
 	}
 
 	if (debug) {
 		struct timespec time_end = {};
 		clock_gettime(CLOCK_MONOTONIC_RAW, &time_end);
 
-		struct rusage usage;
 		getrusage(RUSAGE_SELF, &usage);
 		printf(
 		    "\n"
-		    PROGNAME ": "
+		    PROGNAME ": self    : "
+		    "user=%llu.%06us, system=%llu.%06us, maxrss=%ldB\n",
+		    (unsigned long long) usage.ru_utime.tv_sec,
+		    (unsigned int) usage.ru_utime.tv_usec,
+		    (unsigned long long) usage.ru_stime.tv_sec,
+		    (unsigned int) usage.ru_stime.tv_usec,
+		    usage.ru_maxrss * 1024);
+
+		getrusage(RUSAGE_CHILDREN, &usage);
+		printf(PROGNAME ": children: "
 		    "user=%llu.%06us, system=%llu.%06us, maxrss=%ldB\n",
 		    (unsigned long long) usage.ru_utime.tv_sec,
 		    (unsigned int) usage.ru_utime.tv_usec,
@@ -977,7 +1068,7 @@ main(int argc, char **argv)
 		    time_init.tv_nsec / 1000000000;
 		time_init.tv_nsec %= 1000000000;
 
-		printf(PROGNAME ": "
+		printf(PROGNAME ": wall    : "
 		    "total=%llu.%09llus = "
 		    "init=%llu.%09llus + real=%llu.%09llus\n",
 		    (unsigned long long) time_init.tv_sec,
@@ -986,15 +1077,7 @@ main(int argc, char **argv)
 		    (unsigned long long) time_start.tv_nsec,
 		    (unsigned long long) time_end.tv_sec,
 		    (unsigned long long) time_end.tv_nsec);
-
-		fflush(stdout);
 	}
 
-	if (FREE_STATICS) {
-		closedir(fslist_dir);
-		tdestroy(noauto_files, free);
-		tdestroy(known_pools, free);
-		regfree(&uri_regex);
-	}
 	_exit(ret);
 }
diff --git a/man/man8/zfs-mount-generator.8.in b/man/man8/zfs-mount-generator.8.in
index ae8937038e..7aa332ba81 100644
--- a/man/man8/zfs-mount-generator.8.in
+++ b/man/man8/zfs-mount-generator.8.in
@@ -142,11 +142,22 @@ ZEDLET, if enabled
 .Pq see Xr zed 8 .
 .
 .Sh ENVIRONMENT
-If the
+The
 .Sy ZFS_DEBUG
-environment variable is nonzero
-.Pq or unset and Pa /proc/cmdline No contains Qq Sy debug ,
-print summary accounting information at the end.
+environment variable can either be
+.Sy 0
+(default),
+.Sy 1
+(print summary accounting information at the end), or at least
+.Sy 2
+(print accounting information for each subprocess as it finishes).
+.
+If not present,
+.Pa /proc/cmdline
+is additionally checked for
+.Qq debug ,
+in which case the debug level is set to
+.Sy 2 .
 .
 .Sh EXAMPLES
 To begin, enable tracking for the pool:
-- 
2.32.0