Make txg_wait_synced conditional in zfsvfs_teardown

The call to txg_wait_synced in zfsvfs_teardown should be made conditional on the objset having dirty data. This can prevent unnecessary txg_wait_synced during some unmount operations. Reviewed-by: Matt Ahrens <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Paul Zuchowski <[email protected]> Closes #9115
openzfs · Aug 15, 2019 · e2b31b5 · e2b31b5
1 parent dc04a8c
commit e2b31b5
Showing 1 changed file with 10 additions and 1 deletion.
diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
@@ -1778,8 +1778,17 @@ zfsvfs_teardown(zfsvfs_t *zfsvfs, boolean_t unmounting)
 	 * Evict cached data. We must write out any dirty data before
 	 * disowning the dataset.
 	 */
-	if (!zfs_is_readonly(zfsvfs))
+	objset_t *os = zfsvfs->z_os;
+	boolean_t os_dirty = B_FALSE;
+	for (int t = 0; t < TXG_SIZE; t++) {
+		if (dmu_objset_is_dirty(os, t)) {
+			os_dirty = B_TRUE;
+			break;
+		}
+	}
+	if (!zfs_is_readonly(zfsvfs) && os_dirty) {
 		txg_wait_synced(dmu_objset_pool(zfsvfs->z_os), 0);
+	}
 	dmu_objset_evict_dbufs(zfsvfs->z_os);
 
 	return (0);