[lvm-devel] main - libdm: match reactivation of sibling for snapshot

[Zdenek Kabelac]

Gitweb:        https://sourceware.org/git/?p=lvm2.git;a=commitdiff;h=9b78f7eee9f231d88ed5ca05fbf6da8c473ab41e
Commit:        9b78f7eee9f231d88ed5ca05fbf6da8c473ab41e
Parent:        7e14835a46a6c9e66087d6502d23df53c2a9954f
Author:        Zdenek Kabelac <zkabelac at redhat.com>
AuthorDate:    Sun Feb 12 23:53:18 2023 +0100
Committer:     Zdenek Kabelac <zkabelac at redhat.com>
CommitterDate: Mon Feb 13 13:41:59 2023 +0100

libdm: match reactivation of sibling for snapshot

Apply same code for libdm as in device_mapper dir from
commit c8a5948a71b041ae2cce03e1b3a9843f0fab023f.
---
 libdm/libdm-deptree.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/libdm/libdm-deptree.c b/libdm/libdm-deptree.c
index 33a80cf4d..bb2e53669 100644
--- a/libdm/libdm-deptree.c
+++ b/libdm/libdm-deptree.c
@@ -254,6 +254,10 @@ struct load_properties {
 	unsigned send_messages;
 	/* Skip suspending node's children, used when sending messages to thin-pool */
 	int skip_suspend;
+
+	/* Suspend and Resume siblings after node activation with udev flags*/
+	unsigned reactivate_siblings;
+	uint16_t reactivate_udev_flags;
 };
 
 /* Two of these used to join two nodes with uses and used_by. */
@@ -1877,6 +1881,68 @@ static int _rename_conflict_exists(struct dm_tree_node *parent,
 	return 0;
 }
 
+/*
+ * Reactivation of sibling nodes
+ *
+ * Function is used when activating origin and its thick snapshots
+ * to ensure udev is processing first the origin LV and all the
+ * snapshot LVs are processed afterwards.
+ */
+static int _reactivate_siblings(struct dm_tree_node *dnode,
+				const char *uuid_prefix,
+				size_t uuid_prefix_len)
+{
+	struct dm_tree_node *child;
+	const char *uuid;
+	void *handle = NULL;
+	int r = 1;
+
+	/* Wait for udev before reactivating siblings */
+	if (!dm_udev_wait(dm_tree_get_cookie(dnode)))
+		stack;
+
+	dm_tree_set_cookie(dnode, 0);
+
+	while ((child = dm_tree_next_child(&handle, dnode, 0))) {
+		if (child->props.reactivate_siblings) {
+			/* Skip 'leading' device in this group, marked with flag */
+			child->props.reactivate_siblings = 0;
+			continue;
+		}
+
+		if (!(uuid = dm_tree_node_get_uuid(child))) {
+			stack;
+			continue;
+		}
+
+		if (!_uuid_prefix_matches(uuid, uuid_prefix, uuid_prefix_len))
+			continue;
+
+		if (!_suspend_node(child->name, child->info.major, child->info.minor,
+				   child->dtree->skip_lockfs,
+				   child->dtree->no_flush, &child->info)) {
+			log_error("Unable to suspend %s (" FMTu32
+				  ":" FMTu32 ")", child->name,
+				  child->info.major, child->info.minor);
+			r = 0;
+			continue;
+		}
+		if (!_resume_node(child->name, child->info.major, child->info.minor,
+				  child->props.read_ahead, child->props.read_ahead_flags,
+				  &child->info, &child->dtree->cookie,
+				  child->props.reactivate_udev_flags, // use these flags
+				  child->info.suspended)) {
+			log_error("Failed to suspend %s (" FMTu32
+				  ":" FMTu32 ")", child->name,
+				  child->info.major, child->info.minor);
+			r = 0;
+			continue;
+		}
+	}
+
+	return r;
+}
+
 int dm_tree_activate_children(struct dm_tree_node *dnode,
 				 const char *uuid_prefix,
 				 size_t uuid_prefix_len)
@@ -1965,6 +2031,11 @@ int dm_tree_activate_children(struct dm_tree_node *dnode,
 			if (r && (child->props.send_messages > 1) &&
 			    !(r = _node_send_messages(child, uuid_prefix, uuid_prefix_len, 1)))
 				stack;
+
+			/* Reactivate only for fresh activated origin */
+			if (r && child->props.reactivate_siblings &&
+			    (!(r = _reactivate_siblings(dnode, uuid_prefix, uuid_prefix_len))))
+				stack;
 		}
 		if (awaiting_peer_rename)
 			priority--; /* redo priority level */
@@ -2999,6 +3070,10 @@ int dm_tree_node_add_snapshot_origin_target(struct dm_tree_node *dnode,
 	/* Resume snapshot origins after new snapshots */
 	dnode->activation_priority = 1;
 
+	if (!dnode->info.exists)
+		/* Reactivate siblings for this origin after being resumed */
+		dnode->props.reactivate_siblings = 1;
+
 	/*
 	 * Don't resume the origin immediately in case it is a non-trivial 
 	 * target that must not be active more than once concurrently!
@@ -3061,6 +3136,20 @@ static int _add_snapshot_target(struct dm_tree_node *node,
 			/* Resume merging snapshot after snapshot-merge */
 			seg->merge->activation_priority = 2;
 		}
+	} else if (!origin_node->info.exists) {
+		/* Keep original udev_flags for reactivation. */
+		node->props.reactivate_udev_flags = node->udev_flags;
+
+		/* Reactivation is needed if the origin's -real device is not in DM table.
+		 * For this case after the resume of its origin LV we resume its snapshots
+		 * with updated udev_flags to completely avoid udev scanning for the first resume.
+		 * Reactivation then resumes snapshots with original udev_flags.
+		 */
+		node->udev_flags |= DM_SUBSYSTEM_UDEV_FLAG0 |
+			DM_UDEV_DISABLE_DISK_RULES_FLAG |
+			DM_UDEV_DISABLE_OTHER_RULES_FLAG;
+		log_debug_activation("Using udev_flags 0x%x for activation of %s.",
+				     node->udev_flags, node->name);
 	}
 
 	return 1;