Illumos 3749 - zfs event processing should work on R/O root filesystems

3749 zfs event processing should work on R/O root filesystems
Reviewed by: Matthew Ahrens <[email protected]>
Reviewed by: Eric Schrock <[email protected]>
Approved by: Christopher Siden <[email protected]>

References:
  https://www.illumos.org/issues/3749
  https://github.com/illumos/illumos-gate/commit/3cb69f7

Porting notes:
- [include/sys/spa_impl.h]
  - ffe9d38 Add generic errata infrastructure
  - 1421c89 Add visibility in to arc_read
- [include/sys/fm/fs/zfs.h]
  - 2668527 Add linux events
  - 6283f55 Support custom build directories and move includes
- [module/zfs/spa_config.c]
  - Updated spa_config_sync() to match illumos with the exception
    of a Linux specific block.

Ported-by: kernelOfTruth [email protected]
Signed-off-by: Brian Behlendorf <[email protected]>

1 files changed, 29 insertions, 2 deletions

diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index d7b800adf..ffefbd345 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -82,6 +82,12 @@
 #include "zfs_prop.h"
 #include "zfs_comutil.h"
 
+/*
+ * The interval, in seconds, at which failed configuration cache file writes
+ * should be retried.
+ */
+static int zfs_ccw_retry_interval = 300;
+
 typedef enum zti_modes {
 	ZTI_MODE_FIXED,			/* value is # of threads (min 1) */
 	ZTI_MODE_BATCH,			/* cpu-intensive; value is ignored */
@@ -5912,13 +5918,34 @@ spa_async_resume(spa_t *spa)
 	mutex_exit(&spa->spa_async_lock);
 }
 
+static boolean_t
+spa_async_tasks_pending(spa_t *spa)
+{
+	uint_t non_config_tasks;
+	uint_t config_task;
+	boolean_t config_task_suspended;
+
+	non_config_tasks = spa->spa_async_tasks & ~SPA_ASYNC_CONFIG_UPDATE;
+	config_task = spa->spa_async_tasks & SPA_ASYNC_CONFIG_UPDATE;
+	if (spa->spa_ccw_fail_time == 0) {
+		config_task_suspended = B_FALSE;
+	} else {
+		config_task_suspended =
+		    (gethrtime() - spa->spa_ccw_fail_time) <
+		    (zfs_ccw_retry_interval * NANOSEC);
+	}
+
+	return (non_config_tasks || (config_task && !config_task_suspended));
+}
+
 static void
 spa_async_dispatch(spa_t *spa)
 {
 	mutex_enter(&spa->spa_async_lock);
-	if (spa->spa_async_tasks && !spa->spa_async_suspended &&
+	if (spa_async_tasks_pending(spa) &&
+	    !spa->spa_async_suspended &&
 	    spa->spa_async_thread == NULL &&
-	    rootdir != NULL && !vn_is_readonly(rootdir))
+	    rootdir != NULL)
 		spa->spa_async_thread = thread_create(NULL, 0,
 		    spa_async_thread, spa, 0, &p0, TS_RUN, maxclsyspri);
 	mutex_exit(&spa->spa_async_lock);