Commit 58b47c71 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
Browse files

af_unix: Count cyclic SCC. 



__unix_walk_scc() and unix_walk_scc_fast() call unix_scc_cyclic()
for each SCC to check if it forms a cyclic reference, so that we
can skip GC at the following invocations in case all SCCs do not
have any cycles.

If we count the number of cyclic SCCs in __unix_walk_scc(), we can
simplify unix_walk_scc_fast() because the number of cyclic SCCs
only changes when it garbage-collects a SCC.

So, let's count cyclic SCC in __unix_walk_scc() and decrement it
in unix_walk_scc_fast() when performing garbage collection.

Note that we will use this counter in a later patch to check if a
cycle existed in the previous GC run.

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20251115020935.2643121-2-kuniyu@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent f83e0e0b

net/unix/garbage.c

+21 −10
Original line number Diff line number Diff line
@@ -404,9 +404,11 @@ static bool unix_scc_cyclic(struct list_head *scc) 
static LIST_HEAD(unix_visited_vertices);

static unsigned long unix_vertex_grouped_index = UNIX_VERTEX_INDEX_MARK2;



static void __unix_walk_scc(struct unix_vertex *vertex, unsigned long *last_index,

static unsigned long __unix_walk_scc(struct unix_vertex *vertex,

				     unsigned long *last_index,

				     struct sk_buff_head *hitlist)

{

	unsigned long cyclic_sccs = 0;

	LIST_HEAD(vertex_stack);

	struct unix_edge *edge;

	LIST_HEAD(edge_stack);
@@ -497,8 +499,8 @@ static void __unix_walk_scc(struct unix_vertex *vertex, unsigned long *last_inde 
			if (unix_vertex_max_scc_index < vertex->scc_index)

				unix_vertex_max_scc_index = vertex->scc_index;



			if (!unix_graph_maybe_cyclic)

				unix_graph_maybe_cyclic = unix_scc_cyclic(&scc);

			if (unix_scc_cyclic(&scc))

				cyclic_sccs++;

		}



		list_del(&scc);
@@ -507,13 +509,17 @@ static void __unix_walk_scc(struct unix_vertex *vertex, unsigned long *last_inde 
	/* Need backtracking ? */

	if (!list_empty(&edge_stack))

		goto prev_vertex;



	return cyclic_sccs;

}



static unsigned long unix_graph_cyclic_sccs;



static void unix_walk_scc(struct sk_buff_head *hitlist)

{

	unsigned long last_index = UNIX_VERTEX_INDEX_START;

	unsigned long cyclic_sccs = 0;



	unix_graph_maybe_cyclic = false;

	unix_vertex_max_scc_index = UNIX_VERTEX_INDEX_START;



	/* Visit every vertex exactly once.
@@ -523,18 +529,20 @@ static void unix_walk_scc(struct sk_buff_head *hitlist) 
		struct unix_vertex *vertex;



		vertex = list_first_entry(&unix_unvisited_vertices, typeof(*vertex), entry);

		__unix_walk_scc(vertex, &last_index, hitlist);

		cyclic_sccs += __unix_walk_scc(vertex, &last_index, hitlist);

	}



	list_replace_init(&unix_visited_vertices, &unix_unvisited_vertices);

	swap(unix_vertex_unvisited_index, unix_vertex_grouped_index);



	unix_graph_cyclic_sccs = cyclic_sccs;

	unix_graph_maybe_cyclic = !!unix_graph_cyclic_sccs;

	unix_graph_grouped = true;

}



static void unix_walk_scc_fast(struct sk_buff_head *hitlist)

{

	unix_graph_maybe_cyclic = false;

	unsigned long cyclic_sccs = unix_graph_cyclic_sccs;



	while (!list_empty(&unix_unvisited_vertices)) {

		struct unix_vertex *vertex;
@@ -551,15 +559,18 @@ static void unix_walk_scc_fast(struct sk_buff_head *hitlist) 
				scc_dead = unix_vertex_dead(vertex);

		}



		if (scc_dead)

		if (scc_dead) {

			cyclic_sccs--;

			unix_collect_skb(&scc, hitlist);

		else if (!unix_graph_maybe_cyclic)

			unix_graph_maybe_cyclic = unix_scc_cyclic(&scc);

		}



		list_del(&scc);

	}



	list_replace_init(&unix_visited_vertices, &unix_unvisited_vertices);



	unix_graph_cyclic_sccs = cyclic_sccs;

	unix_graph_maybe_cyclic = !!unix_graph_cyclic_sccs;

}



static bool gc_in_progress;