Re-initialize objsets when feature@project_quota is enabled

Addresses the issue of project quotas not being usable after pool
upgrade coming from an older version which does not support project
quotas to the one that does, similarly to how it was solved for user
quotas back in the day with `zfs set version=current` -- when
feature@project_quota is first enabled, re-initialize the pool's
objsets.

Signed-off-by: Dušan Gvozdenović <dusan.gvozdenovic.99@gmail.com>
Closes #17955

Author: dusan-gvozdenovic

include/sys/dmu_objset.h

@@ -261,6 +261,7 @@ boolean_t dmu_objset_projectquota_enabled(objset_t *os);
 boolean_t dmu_objset_projectquota_present(objset_t *os);
 boolean_t dmu_objset_projectquota_upgradable(objset_t *os);
 void dmu_objset_id_quota_upgrade(objset_t *os);
+void dmu_objset_id_projectquota_upgrade(objset_t *os);
 int dmu_get_file_info(objset_t *os, dmu_object_type_t bonustype,
     const void *data, zfs_file_info_t *zfi);
 

module/zfs/dmu_objset.c

@@ -2439,6 +2439,30 @@ dmu_objset_id_quota_upgrade(objset_t *os)
 	dmu_objset_upgrade(os, dmu_objset_id_quota_upgrade_cb);
 }
 
+static int
+dmu_objset_id_projectquota_upgrade_cb(objset_t *os)
+{
+	if (dmu_objset_projectquota_present(os))
+		return (0);
+	if (!dmu_objset_projectquota_enabled(os))
+		return (SET_ERROR(ENOTSUP));
+
+	dmu_objset_ds(os)->ds_feature_activation[
+	    SPA_FEATURE_PROJECT_QUOTA] = (void *)B_TRUE;
+
+	if (dmu_objset_projectquota_enabled(os))
+		os->os_flags |= OBJSET_FLAG_PROJECTQUOTA_COMPLETE;
+
+	txg_wait_synced(dmu_objset_pool(os), 0);
+	return (0);
+}
+
+void
+dmu_objset_id_projectquota_upgrade(objset_t *os)
+{
+	dmu_objset_upgrade(os, dmu_objset_id_projectquota_upgrade_cb);
+}
+
 boolean_t
 dmu_objset_userobjspace_upgradable(objset_t *os)
 {

module/zfs/zfs_ioctl.c

@@ -3104,6 +3104,67 @@ zfs_ioc_inherit_prop(zfs_cmd_t *zc)
 	return (err);
 }
 
+static int
+zfs_projectquota_upgrade_cb(const char *dataset, void *arg)
+{
+	zfsvfs_t *zfsvfs;
+	int error;
+
+	(void) arg;
+
+	error = getzfsvfs(dataset, &zfsvfs);
+
+	if (error != 0)
+		return (0);
+
+	if (!dmu_objset_projectquota_enabled(zfsvfs->z_os)) {
+		/*
+		 * If projectquota is not enabled, it may be because the objset
+		 * needs to be closed & reopened (to grow the objset_phys_t).
+		 * Suspend/resume the fs will do that.
+		 */
+		dsl_dataset_t *ds, *newds;
+
+		ds = dmu_objset_ds(zfsvfs->z_os);
+		error = zfs_suspend_fs(zfsvfs);
+		if (error == 0) {
+			dmu_objset_refresh_ownership(ds, &newds,
+			    B_TRUE, zfsvfs);
+			error = zfs_resume_fs(zfsvfs, newds);
+		}
+	}
+
+	if (error == 0) {
+		mutex_enter(&zfsvfs->z_os->os_upgrade_lock);
+		if (zfsvfs->z_os->os_upgrade_id == 0) {
+			/* clear potential error code and retry */
+			zfsvfs->z_os->os_upgrade_status = 0;
+			mutex_exit(&zfsvfs->z_os->os_upgrade_lock);
+
+			dsl_pool_config_enter(
+			    dmu_objset_pool(zfsvfs->z_os), FTAG);
+			dmu_objset_id_projectquota_upgrade(zfsvfs->z_os);
+			dsl_pool_config_exit(
+			    dmu_objset_pool(zfsvfs->z_os), FTAG);
+		} else {
+			mutex_exit(&zfsvfs->z_os->os_upgrade_lock);
+		}
+
+		taskq_wait_id(zfsvfs->z_os->os_spa->spa_upgrade_taskq,
+		    zfsvfs->z_os->os_upgrade_id);
+		error = zfsvfs->z_os->os_upgrade_status;
+	}
+
+	zfs_vfs_rele(zfsvfs);
+
+	if (error != 0)
+		cmn_err(CE_WARN,
+		    "Failed to activate the project quota feature on dataset "
+		    "%s (%d).", dataset, error);
+
+	return (0);
+}
+
 static int
 zfs_ioc_pool_set_props(zfs_cmd_t *zc)
 {
@@ -3143,6 +3204,16 @@ zfs_ioc_pool_set_props(zfs_cmd_t *zc)
 
 	error = spa_prop_set(spa, props);
 
+	/*
+	 * If we are enabling the project quota feature, try to re-initialize
+	 * the active file systems on that pool and activate the feature -- all
+	 * in best effort.
+	 */
+	if ((error == 0) && nvlist_exists(props, "feature@project_quota"))
+		(void) dmu_objset_find(spa_name(spa),
+		    zfs_projectquota_upgrade_cb,
+		    NULL, DS_FIND_CHILDREN);
+
 	nvlist_free(props);
 	spa_close(spa, FTAG);