Retire zfs_autoimport_disable kmod option

Back in 2014 the zfs_autoimport_disable module option was added to
control whether the kmods should load the pool configs from the cache
file on module load.  The default value since that time has been for
the kernel to not process the cache file.

Detecting and importing pools during boot is now controlled outside
of the kmod on both Linux and FreeBSD.  By all accounts this has been
working well and we can remove this dormant code on the kernel side.

The spa_config_load() function is has been moved to userspace, it is
now only used by libzpool.  Additionally, the spa_boot_init() hook
which was used by FreeBSD now looks to be used and was removed.

Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #17618

include/sys/spa.h

@@ -880,7 +880,6 @@ extern kcondvar_t spa_namespace_cv;
 #define	SPA_CONFIG_UPDATE_VDEVS	1
 
 extern void spa_write_cachefile(spa_t *, boolean_t, boolean_t, boolean_t);
-extern void spa_config_load(void);
 extern int spa_all_configs(uint64_t *generation, nvlist_t **pools);
 extern void spa_config_set(spa_t *spa, nvlist_t *config);
 extern nvlist_t *spa_config_generate(spa_t *spa, vdev_t *vd, uint64_t txg,
@@ -1244,7 +1243,6 @@ extern void vdev_mirror_stat_fini(void);
 /* Initialization and termination */
 extern void spa_init(spa_mode_t mode);
 extern void spa_fini(void);
-extern void spa_boot_init(void *);
 
 /* properties */
 extern int spa_prop_set(spa_t *spa, nvlist_t *nvp);

lib/libzpool/kernel.c

@@ -38,6 +38,7 @@
 #include <sys/processor.h>
 #include <sys/rrwlock.h>
 #include <sys/spa.h>
+#include <sys/spa_impl.h>
 #include <sys/stat.h>
 #include <sys/systeminfo.h>
 #include <sys/time.h>
@@ -811,6 +812,79 @@ umem_out_of_memory(void)
 	return (0);
 }
 
+static void
+spa_config_load(void)
+{
+	void *buf = NULL;
+	nvlist_t *nvlist, *child;
+	nvpair_t *nvpair;
+	char *pathname;
+	zfs_file_t *fp;
+	zfs_file_attr_t zfa;
+	uint64_t fsize;
+	int err;
+
+	/*
+	 * Open the configuration file.
+	 */
+	pathname = kmem_alloc(MAXPATHLEN, KM_SLEEP);
+
+	(void) snprintf(pathname, MAXPATHLEN, "%s", spa_config_path);
+
+	err = zfs_file_open(pathname, O_RDONLY, 0, &fp);
+	if (err)
+		err = zfs_file_open(ZPOOL_CACHE_BOOT, O_RDONLY, 0, &fp);
+
+	kmem_free(pathname, MAXPATHLEN);
+
+	if (err)
+		return;
+
+	if (zfs_file_getattr(fp, &zfa))
+		goto out;
+
+	fsize = zfa.zfa_size;
+	buf = kmem_alloc(fsize, KM_SLEEP);
+
+	/*
+	 * Read the nvlist from the file.
+	 */
+	if (zfs_file_read(fp, buf, fsize, NULL) < 0)
+		goto out;
+
+	/*
+	 * Unpack the nvlist.
+	 */
+	if (nvlist_unpack(buf, fsize, &nvlist, KM_SLEEP) != 0)
+		goto out;
+
+	/*
+	 * Iterate over all elements in the nvlist, creating a new spa_t for
+	 * each one with the specified configuration.
+	 */
+	mutex_enter(&spa_namespace_lock);
+	nvpair = NULL;
+	while ((nvpair = nvlist_next_nvpair(nvlist, nvpair)) != NULL) {
+		if (nvpair_type(nvpair) != DATA_TYPE_NVLIST)
+			continue;
+
+		child = fnvpair_value_nvlist(nvpair);
+
+		if (spa_lookup(nvpair_name(nvpair)) != NULL)
+			continue;
+		(void) spa_add(nvpair_name(nvpair), child, NULL);
+	}
+	mutex_exit(&spa_namespace_lock);
+
+	nvlist_free(nvlist);
+
+out:
+	if (buf != NULL)
+		kmem_free(buf, fsize);
+
+	zfs_file_close(fp);
+}
+
 void
 kernel_init(int mode)
 {
@@ -835,6 +909,7 @@ kernel_init(int mode)
 	zstd_init();
 
 	spa_init((spa_mode_t)mode);
+	spa_config_load();
 
 	fletcher_4_init();
 

man/man4/zfs.4

@@ -941,10 +941,6 @@ The target number of bytes the ARC should leave as free memory on the system.
 If zero, equivalent to the bigger of
 .Sy 512 KiB No and Sy all_system_memory/64 .
 .
-.It Sy zfs_autoimport_disable Ns = Ns Sy 1 Ns | Ns 0 Pq int
-Disable pool import at module load by ignoring the cache file
-.Pq Sy spa_config_path .
-.
 .It Sy zfs_checksum_events_per_second Ns = Ns Sy 20 Ns /s Pq uint
 Rate limit checksum events to this many per second.
 Note that this should not be set below the ZED thresholds

module/os/freebsd/zfs/kmod_core.c

@@ -112,7 +112,6 @@ static int zfs__fini(void);
 static void zfs_shutdown(void *, int);
 
 static eventhandler_tag zfs_shutdown_event_tag;
-static eventhandler_tag zfs_mountroot_event_tag;
 
 #define	ZFS_MIN_KSTACK_PAGES 4
 
@@ -311,9 +310,6 @@ zfs_modevent(module_t mod, int type, void *unused __unused)
 			zfs_shutdown_event_tag = EVENTHANDLER_REGISTER(
 			    shutdown_post_sync, zfs_shutdown, NULL,
 			    SHUTDOWN_PRI_FIRST);
-			zfs_mountroot_event_tag = EVENTHANDLER_REGISTER(
-			    mountroot, spa_boot_init, NULL,
-			    SI_ORDER_ANY);
 		}
 		return (err);
 	case MOD_UNLOAD:
@@ -322,9 +318,6 @@ zfs_modevent(module_t mod, int type, void *unused __unused)
 			if (zfs_shutdown_event_tag != NULL)
 				EVENTHANDLER_DEREGISTER(shutdown_post_sync,
 				    zfs_shutdown_event_tag);
-			if (zfs_mountroot_event_tag != NULL)
-				EVENTHANDLER_DEREGISTER(mountroot,
-				    zfs_mountroot_event_tag);
 		}
 		return (err);
 	case MOD_SHUTDOWN:

module/zfs/spa_config.c

@@ -48,18 +48,17 @@
 /*
  * Pool configuration repository.
  *
- * Pool configuration is stored as a packed nvlist on the filesystem.  By
- * default, all pools are stored in /etc/zfs/zpool.cache and loaded on boot
- * (when the ZFS module is loaded).  Pools can also have the 'cachefile'
- * property set that allows them to be stored in an alternate location until
- * the control of external software.
+ * Pool configuration is stored as a packed nvlist on the filesystem.  When
+ * pools are imported they are added to the /etc/zfs/zpool.cache file and
+ * removed from it when exported.  For each cache file, we have a single nvlist
+ * which holds all the configuration information.  Pools can also have the
+ * 'cachefile' property set which allows this config to be stored in an
+ * alternate location under the control of external software.
  *
- * For each cache file, we have a single nvlist which holds all the
- * configuration information.  When the module loads, we read this information
- * from /etc/zfs/zpool.cache and populate the SPA namespace.  This namespace is
- * maintained independently in spa.c.  Whenever the namespace is modified, or
- * the configuration of a pool is changed, we call spa_write_cachefile(), which
- * walks through all the active pools and writes the configuration to disk.
+ * The kernel independantly maintains an AVL tree of imported pools.  See the
+ * "SPA locking" comment in spa.c.  Whenever a pool configuration is modified
+ * we call spa_write_cachefile() which walks through all the active pools and
+ * writes the updated configuration to to /etc/zfs/zpool.cache file.
  */
 
 static uint64_t spa_config_generation = 1;
@@ -69,94 +68,6 @@ static uint64_t spa_config_generation = 1;
  * userland pools when doing testing.
  */
 char *spa_config_path = (char *)ZPOOL_CACHE;
-#ifdef _KERNEL
-static int zfs_autoimport_disable = B_TRUE;
-#endif
-
-/*
- * Called when the module is first loaded, this routine loads the configuration
- * file into the SPA namespace.  It does not actually open or load the pools; it
- * only populates the namespace.
- */
-void
-spa_config_load(void)
-{
-	void *buf = NULL;
-	nvlist_t *nvlist, *child;
-	nvpair_t *nvpair;
-	char *pathname;
-	zfs_file_t *fp;
-	zfs_file_attr_t zfa;
-	uint64_t fsize;
-	int err;
-
-#ifdef _KERNEL
-	if (zfs_autoimport_disable)
-		return;
-#endif
-
-	/*
-	 * Open the configuration file.
-	 */
-	pathname = kmem_alloc(MAXPATHLEN, KM_SLEEP);
-
-	(void) snprintf(pathname, MAXPATHLEN, "%s", spa_config_path);
-
-	err = zfs_file_open(pathname, O_RDONLY, 0, &fp);
-
-#ifdef __FreeBSD__
-	if (err)
-		err = zfs_file_open(ZPOOL_CACHE_BOOT, O_RDONLY, 0, &fp);
-#endif
-	kmem_free(pathname, MAXPATHLEN);
-
-	if (err)
-		return;
-
-	if (zfs_file_getattr(fp, &zfa))
-		goto out;
-
-	fsize = zfa.zfa_size;
-	buf = kmem_alloc(fsize, KM_SLEEP);
-
-	/*
-	 * Read the nvlist from the file.
-	 */
-	if (zfs_file_read(fp, buf, fsize, NULL) < 0)
-		goto out;
-
-	/*
-	 * Unpack the nvlist.
-	 */
-	if (nvlist_unpack(buf, fsize, &nvlist, KM_SLEEP) != 0)
-		goto out;
-
-	/*
-	 * Iterate over all elements in the nvlist, creating a new spa_t for
-	 * each one with the specified configuration.
-	 */
-	mutex_enter(&spa_namespace_lock);
-	nvpair = NULL;
-	while ((nvpair = nvlist_next_nvpair(nvlist, nvpair)) != NULL) {
-		if (nvpair_type(nvpair) != DATA_TYPE_NVLIST)
-			continue;
-
-		child = fnvpair_value_nvlist(nvpair);
-
-		if (spa_lookup(nvpair_name(nvpair)) != NULL)
-			continue;
-		(void) spa_add(nvpair_name(nvpair), child, NULL);
-	}
-	mutex_exit(&spa_namespace_lock);
-
-	nvlist_free(nvlist);
-
-out:
-	if (buf != NULL)
-		kmem_free(buf, fsize);
-
-	zfs_file_close(fp);
-}
 
 static int
 spa_config_remove(spa_config_dirent_t *dp)
@@ -623,7 +534,6 @@ spa_config_update(spa_t *spa, int what)
 		spa_config_update(spa, SPA_CONFIG_UPDATE_VDEVS);
 }
 
-EXPORT_SYMBOL(spa_config_load);
 EXPORT_SYMBOL(spa_all_configs);
 EXPORT_SYMBOL(spa_config_set);
 EXPORT_SYMBOL(spa_config_generate);
@@ -634,8 +544,3 @@ EXPORT_SYMBOL(spa_config_update);
 ZFS_MODULE_PARAM(zfs_spa, spa_, config_path, STRING, ZMOD_RD,
 	"SPA config file (/etc/zfs/zpool.cache)");
 #endif
-
-#ifdef _KERNEL
-ZFS_MODULE_PARAM(zfs, zfs_, autoimport_disable, INT, ZMOD_RW,
-	"Disable pool import at module load");
-#endif

module/zfs/spa_misc.c

@@ -2547,13 +2547,6 @@ spa_name_compare(const void *a1, const void *a2)
 	return (TREE_ISIGN(s));
 }
 
-void
-spa_boot_init(void *unused)
-{
-	(void) unused;
-	spa_config_load();
-}
-
 void
 spa_init(spa_mode_t mode)
 {
@@ -2607,7 +2600,6 @@ spa_init(spa_mode_t mode)
 	chksum_init();
 	zpool_prop_init();
 	zpool_feature_init();
-	spa_config_load();
 	vdev_prop_init();
 	l2arc_start();
 	scan_init();