+ * Jobid can be set for a session (see setsid(2)) by writing to
+ * a sysfs file from any process in that session.
+ * The jobids are stored in a hash table indexed by the relevant
+ * struct pid. We periodically look for entries where the pid has
+ * no PIDTYPE_SID tasks any more, and prune them. This happens within
+ * 5 seconds of a jobid being added, and every 5 minutes when jobids exist,
+ * but none are added.
+ */
+#define JOBID_EXPEDITED_CLEAN (5)
+#define JOBID_BACKGROUND_CLEAN (5 * 60)
+
+struct session_jobid {
+ struct pid *sj_session;
+ struct rhash_head sj_linkage;
+ struct rcu_head sj_rcu;
+ char sj_jobid[1];
+};
+
+static const struct rhashtable_params jobid_params = {
+ .key_len = sizeof(struct pid *),
+ .key_offset = offsetof(struct session_jobid, sj_session),
+ .head_offset = offsetof(struct session_jobid, sj_linkage),
+};
+
+static struct rhashtable session_jobids;
+
+/*
+ * jobid_current must be called with rcu_read_lock held.
+ * if it returns non-NULL, the string can only be used
+ * until rcu_read_unlock is called.
+ */
+char *jobid_current(void)
+{
+ struct pid *sid = task_session(current);
+ struct session_jobid *sj;
+
+ sj = rhashtable_lookup_fast(&session_jobids, &sid, jobid_params);
+ if (sj)
+ return sj->sj_jobid;
+ return NULL;
+}
+
+static void jobid_prune_expedite(void);
+/*
+ * jobid_set_current will try to add a new entry
+ * to the table. If one exists with the same key, the
+ * jobid will be replaced
+ */
+int jobid_set_current(char *jobid)
+{
+ struct pid *sid;
+ struct session_jobid *sj, *origsj;
+ int ret;
+ int len = strlen(jobid);
+
+ sj = kmalloc(sizeof(*sj) + len, GFP_KERNEL);
+ if (!sj)
+ return -ENOMEM;
+ rcu_read_lock();
+ sid = task_session(current);
+ sj->sj_session = get_pid(sid);
+ strncpy(sj->sj_jobid, jobid, len+1);
+ origsj = rhashtable_lookup_get_insert_fast(&session_jobids,
+ &sj->sj_linkage,
+ jobid_params);
+ if (origsj == NULL) {
+ /* successful insert */
+ rcu_read_unlock();
+ jobid_prune_expedite();
+ return 0;
+ }
+
+ if (IS_ERR(origsj)) {
+ put_pid(sj->sj_session);
+ kfree(sj);
+ rcu_read_unlock();
+ return PTR_ERR(origsj);
+ }
+ ret = rhashtable_replace_fast(&session_jobids,
+ &origsj->sj_linkage,
+ &sj->sj_linkage,
+ jobid_params);
+ if (ret) {
+ put_pid(sj->sj_session);
+ kfree(sj);
+ rcu_read_unlock();
+ return ret;
+ }
+ put_pid(origsj->sj_session);
+ rcu_read_unlock();
+ kfree_rcu(origsj, sj_rcu);
+ jobid_prune_expedite();
+
+ return 0;
+}
+
+static void jobid_free(void *vsj, void *arg)
+{
+ struct session_jobid *sj = vsj;
+
+ put_pid(sj->sj_session);
+ kfree(sj);
+}
+
+static void jobid_prune(struct work_struct *work);
+static DECLARE_DELAYED_WORK(jobid_prune_work, jobid_prune);
+static int jobid_prune_expedited;
+static void jobid_prune(struct work_struct *work)
+{
+ int remaining = 0;
+ struct rhashtable_iter iter;
+ struct session_jobid *sj;
+
+ jobid_prune_expedited = 0;
+ rhashtable_walk_enter(&session_jobids, &iter);
+ rhashtable_walk_start(&iter);
+ while ((sj = rhashtable_walk_next(&iter)) != NULL) {
+ if (!hlist_empty(&sj->sj_session->tasks[PIDTYPE_SID])) {
+ remaining++;
+ continue;
+ }
+ if (rhashtable_remove_fast(&session_jobids,
+ &sj->sj_linkage,
+ jobid_params) == 0) {
+ put_pid(sj->sj_session);
+ kfree_rcu(sj, sj_rcu);
+ }
+ }
+ rhashtable_walk_stop(&iter);
+ rhashtable_walk_exit(&iter);
+ if (remaining)
+ schedule_delayed_work(&jobid_prune_work,
+ cfs_time_seconds(JOBID_BACKGROUND_CLEAN));
+}
+
+static void jobid_prune_expedite(void)
+{
+ if (!jobid_prune_expedited) {
+ jobid_prune_expedited = 1;
+ mod_delayed_work(system_wq, &jobid_prune_work,
+ cfs_time_seconds(JOBID_EXPEDITED_CLEAN));
+ }
+}
+
+/*
git://git.whamcloud.com / fs / lustre-release.git / commitdiff