core, systemctl: add support for irreversible jobs

Add a new job mode: replace-irreversibly. Jobs enqueued using this mode
cannot be implicitly canceled by later enqueued conflicting jobs.
They can however still be canceled with an explicit "systemctl cancel"
call.

5 files changed, 29 insertions, 13 deletions

diff --git a/src/core/job.c b/src/core/job.c
index 2bafbc1589..990607f990 100644
--- a/src/core/job.c
+++ b/src/core/job.c
@@ -169,6 +169,7 @@ static void job_merge_into_installed(Job *j, Job *other) {
                 assert(other->type == JOB_NOP);
 
         j->override = j->override || other->override;
+        j->irreversible = j->irreversible || other->irreversible;
         j->ignore_order = j->ignore_order || other->ignore_order;
 }
 
@@ -294,11 +295,13 @@ void job_dump(Job *j, FILE*f, const char *prefix) {
                 "%s-> Job %u:\n"
                 "%s\tAction: %s -> %s\n"
                 "%s\tState: %s\n"
-                "%s\tForced: %s\n",
+                "%s\tForced: %s\n"
+                "%s\tIrreversible: %s\n",
                 prefix, j->id,
                 prefix, j->unit->id, job_type_to_string(j->type),
                 prefix, job_state_to_string(j->state),
-                prefix, yes_no(j->override));
+                prefix, yes_no(j->override),
+                prefix, yes_no(j->irreversible));
 }
 
 /*
@@ -947,6 +950,7 @@ int job_serialize(Job *j, FILE *f, FDSet *fds) {
         fprintf(f, "job-type=%s\n", job_type_to_string(j->type));
         fprintf(f, "job-state=%s\n", job_state_to_string(j->state));
         fprintf(f, "job-override=%s\n", yes_no(j->override));
+        fprintf(f, "job-irreversible=%s\n", yes_no(j->irreversible));
         fprintf(f, "job-sent-dbus-new-signal=%s\n", yes_no(j->sent_dbus_new_signal));
         fprintf(f, "job-ignore-order=%s\n", yes_no(j->ignore_order));
         /* Cannot save bus clients. Just note the fact that we're losing
@@ -1014,6 +1018,12 @@ int job_deserialize(Job *j, FILE *f, FDSet *fds) {
                                 log_debug("Failed to parse job override flag %s", v);
                         else
                                 j->override = j->override || b;
+                } else if (streq(l, "job-irreversible")) {
+                        int b = parse_boolean(v);
+                        if (b < 0)
+                                log_debug("Failed to parse job irreversible flag %s", v);
+                        else
+                                j->irreversible = j->irreversible || b;
                 } else if (streq(l, "job-sent-dbus-new-signal")) {
                         int b = parse_boolean(v);
                         if (b < 0)
@@ -1110,6 +1120,7 @@ DEFINE_STRING_TABLE_LOOKUP(job_type, JobType);
 static const char* const job_mode_table[_JOB_MODE_MAX] = {
         [JOB_FAIL] = "fail",
         [JOB_REPLACE] = "replace",
+        [JOB_REPLACE_IRREVERSIBLY] = "replace-irreversibly",
         [JOB_ISOLATE] = "isolate",
         [JOB_IGNORE_DEPENDENCIES] = "ignore-dependencies",
         [JOB_IGNORE_REQUIREMENTS] = "ignore-requirements"
diff --git a/src/core/job.h b/src/core/job.h
index d10e6b6b0e..45d0487451 100644
--- a/src/core/job.h
+++ b/src/core/job.h
@@ -83,6 +83,7 @@ enum JobState {
 enum JobMode {
         JOB_FAIL,                /* Fail if a conflicting job is already queued */
         JOB_REPLACE,             /* Replace an existing conflicting job */
+        JOB_REPLACE_IRREVERSIBLY, /* Like JOB_REPLACE + produce irreversible jobs */
         JOB_ISOLATE,             /* Start a unit, and stop all others */
         JOB_IGNORE_DEPENDENCIES, /* Ignore both requirement and ordering dependencies */
         JOB_IGNORE_REQUIREMENTS, /* Ignore requirement dependencies */
@@ -161,6 +162,7 @@ struct Job {
         bool sent_dbus_new_signal:1;
         bool ignore_order:1;
         bool forgot_bus_clients:1;
+        bool irreversible:1;
 };
 
 JobBusClient* job_bus_client_new(DBusConnection *connection, const char *name);
diff --git a/src/core/manager.c b/src/core/manager.c
index 28f169daab..a578813617 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -766,7 +766,7 @@ int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool ove
 
         job_type_collapse(&type, unit);
 
-        tr = transaction_new();
+        tr = transaction_new(mode == JOB_REPLACE_IRREVERSIBLY);
         if (!tr)
                 return -ENOMEM;
 
diff --git a/src/core/transaction.c b/src/core/transaction.c
index dbc30af7d1..0329366350 100644
--- a/src/core/transaction.c
+++ b/src/core/transaction.c
@@ -97,6 +97,7 @@ static void transaction_merge_and_delete_job(Transaction *tr, Job *j, Job *other
         j->type = t;
         j->state = JOB_WAITING;
         j->override = j->override || other->override;
+        j->irreversible = j->irreversible || other->irreversible;
 
         j->matters_to_anchor = j->matters_to_anchor || other->matters_to_anchor;
 
@@ -488,7 +489,7 @@ rescan:
         }
 }
 
-static int transaction_is_destructive(Transaction *tr, DBusError *e) {
+static int transaction_is_destructive(Transaction *tr, JobMode mode, DBusError *e) {
         Iterator i;
         Job *j;
 
@@ -503,7 +504,7 @@ static int transaction_is_destructive(Transaction *tr, DBusError *e) {
                 assert(!j->transaction_prev);
                 assert(!j->transaction_next);
 
-                if (j->unit->job &&
+                if (j->unit->job && (mode == JOB_FAIL || j->unit->job->irreversible) &&
                     !job_type_is_superset(j->type, j->unit->job->type)) {
 
                         dbus_set_error(e, BUS_ERROR_TRANSACTION_IS_DESTRUCTIVE, "Transaction is destructive.");
@@ -709,12 +710,10 @@ int transaction_activate(Transaction *tr, Manager *m, JobMode mode, DBusError *e
         transaction_drop_redundant(tr);
 
         /* Ninth step: check whether we can actually apply this */
-        if (mode == JOB_FAIL) {
-                r = transaction_is_destructive(tr, e);
-                if (r < 0) {
-                        log_notice("Requested transaction contradicts existing jobs: %s", bus_error(e, r));
-                        return r;
-                }
+        r = transaction_is_destructive(tr, mode, e);
+        if (r < 0) {
+                log_notice("Requested transaction contradicts existing jobs: %s", bus_error(e, r));
+                return r;
         }
 
         /* Tenth step: apply changes */
@@ -770,6 +769,7 @@ static Job* transaction_add_one_job(Transaction *tr, JobType type, Unit *unit, b
         j->marker = NULL;
         j->matters_to_anchor = false;
         j->override = override;
+        j->irreversible = tr->irreversible;
 
         LIST_PREPEND(Job, transaction, f, j);
 
@@ -1106,7 +1106,7 @@ int transaction_add_isolate_jobs(Transaction *tr, Manager *m) {
         return 0;
 }
 
-Transaction *transaction_new(void) {
+Transaction *transaction_new(bool irreversible) {
         Transaction *tr;
 
         tr = new0(Transaction, 1);
@@ -1119,6 +1119,8 @@ Transaction *transaction_new(void) {
                 return NULL;
         }
 
+        tr->irreversible = irreversible;
+
         return tr;
 }
 
diff --git a/src/core/transaction.h b/src/core/transaction.h
index 67ace4da0b..12f9194927 100644
--- a/src/core/transaction.h
+++ b/src/core/transaction.h
@@ -33,9 +33,10 @@ struct Transaction {
         /* Jobs to be added */
         Hashmap *jobs;      /* Unit object => Job object list 1:1 */
         Job *anchor_job;      /* the job the user asked for */
+        bool irreversible;
 };
 
-Transaction *transaction_new(void);
+Transaction *transaction_new(bool irreversible);
 void transaction_free(Transaction *tr);
 
 int transaction_add_job_and_dependencies(