af_unix: Replace garbage collection algorithm.
If we find a dead SCC during iteration, we call unix_collect_skb() to splice all skb in the SCC to the global sk_buff_head, hitlist. After iterating all SCC, we unlock unix_gc_lock and purge the queue. Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Acked-by: Paolo Abeni <pabeni@redhat.com> Link: https://lore.kernel.org/r/20240325202425.60930-15-kuniyu@amazon.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
Jakub Kicinski
parent
a15702d8b3
commit
4090fa373f
@ -19,9 +19,6 @@ static inline struct unix_sock *unix_get_socket(struct file *filp)
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extern spinlock_t unix_gc_lock;
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extern unsigned int unix_tot_inflight;
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void unix_inflight(struct user_struct *user, struct file *fp);
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void unix_notinflight(struct user_struct *user, struct file *fp);
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void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver);
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void unix_del_edges(struct scm_fp_list *fpl);
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void unix_update_edges(struct unix_sock *receiver);
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@ -85,12 +82,7 @@ struct unix_sock {
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struct sock *peer;
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struct sock *listener;
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struct unix_vertex *vertex;
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struct list_head link;
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unsigned long inflight;
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spinlock_t lock;
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unsigned long gc_flags;
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#define UNIX_GC_CANDIDATE 0
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#define UNIX_GC_MAYBE_CYCLE 1
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struct socket_wq peer_wq;
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wait_queue_entry_t peer_wake;
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struct scm_stat scm_stat;
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@ -980,12 +980,10 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern,
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sk->sk_destruct = unix_sock_destructor;
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u = unix_sk(sk);
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u->listener = NULL;
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u->inflight = 0;
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u->vertex = NULL;
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u->path.dentry = NULL;
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u->path.mnt = NULL;
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spin_lock_init(&u->lock);
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INIT_LIST_HEAD(&u->link);
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mutex_init(&u->iolock); /* single task reading lock */
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mutex_init(&u->bindlock); /* single task binding lock */
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init_waitqueue_head(&u->peer_wait);
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@ -1793,8 +1791,6 @@ static inline bool too_many_unix_fds(struct task_struct *p)
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static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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{
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int i;
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if (too_many_unix_fds(current))
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return -ETOOMANYREFS;
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@ -1806,9 +1802,6 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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if (!UNIXCB(skb).fp)
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return -ENOMEM;
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for (i = scm->fp->count - 1; i >= 0; i--)
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unix_inflight(scm->fp->user, scm->fp->fp[i]);
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if (unix_prepare_fpl(UNIXCB(skb).fp))
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return -ENOMEM;
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@ -1817,15 +1810,10 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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static void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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{
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int i;
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scm->fp = UNIXCB(skb).fp;
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UNIXCB(skb).fp = NULL;
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unix_destroy_fpl(scm->fp);
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for (i = scm->fp->count - 1; i >= 0; i--)
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unix_notinflight(scm->fp->user, scm->fp->fp[i]);
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}
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static void unix_peek_fds(struct scm_cookie *scm, struct sk_buff *skb)
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@ -322,6 +322,52 @@ static bool unix_vertex_dead(struct unix_vertex *vertex)
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return true;
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}
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enum unix_recv_queue_lock_class {
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U_RECVQ_LOCK_NORMAL,
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U_RECVQ_LOCK_EMBRYO,
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};
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static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist)
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{
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struct unix_vertex *vertex;
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list_for_each_entry_reverse(vertex, scc, scc_entry) {
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struct sk_buff_head *queue;
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struct unix_edge *edge;
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struct unix_sock *u;
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edge = list_first_entry(&vertex->edges, typeof(*edge), vertex_entry);
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u = edge->predecessor;
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queue = &u->sk.sk_receive_queue;
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spin_lock(&queue->lock);
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if (u->sk.sk_state == TCP_LISTEN) {
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struct sk_buff *skb;
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skb_queue_walk(queue, skb) {
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struct sk_buff_head *embryo_queue = &skb->sk->sk_receive_queue;
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/* listener -> embryo order, the inversion never happens. */
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spin_lock_nested(&embryo_queue->lock, U_RECVQ_LOCK_EMBRYO);
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skb_queue_splice_init(embryo_queue, hitlist);
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spin_unlock(&embryo_queue->lock);
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}
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} else {
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skb_queue_splice_init(queue, hitlist);
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#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
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if (u->oob_skb) {
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kfree_skb(u->oob_skb);
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u->oob_skb = NULL;
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}
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#endif
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}
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spin_unlock(&queue->lock);
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}
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}
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static bool unix_scc_cyclic(struct list_head *scc)
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{
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struct unix_vertex *vertex;
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@ -345,7 +391,8 @@ static bool unix_scc_cyclic(struct list_head *scc)
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static LIST_HEAD(unix_visited_vertices);
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static unsigned long unix_vertex_grouped_index = UNIX_VERTEX_INDEX_MARK2;
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static void __unix_walk_scc(struct unix_vertex *vertex, unsigned long *last_index)
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static void __unix_walk_scc(struct unix_vertex *vertex, unsigned long *last_index,
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struct sk_buff_head *hitlist)
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{
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LIST_HEAD(vertex_stack);
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struct unix_edge *edge;
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@ -430,7 +477,9 @@ prev_vertex:
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scc_dead = unix_vertex_dead(vertex);
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}
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if (!unix_graph_maybe_cyclic)
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if (scc_dead)
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unix_collect_skb(&scc, hitlist);
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else if (!unix_graph_maybe_cyclic)
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unix_graph_maybe_cyclic = unix_scc_cyclic(&scc);
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list_del(&scc);
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@ -441,7 +490,7 @@ prev_vertex:
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goto prev_vertex;
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}
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static void unix_walk_scc(void)
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static void unix_walk_scc(struct sk_buff_head *hitlist)
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{
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unsigned long last_index = UNIX_VERTEX_INDEX_START;
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@ -454,7 +503,7 @@ static void unix_walk_scc(void)
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struct unix_vertex *vertex;
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vertex = list_first_entry(&unix_unvisited_vertices, typeof(*vertex), entry);
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__unix_walk_scc(vertex, &last_index);
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__unix_walk_scc(vertex, &last_index, hitlist);
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}
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list_replace_init(&unix_visited_vertices, &unix_unvisited_vertices);
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@ -463,7 +512,7 @@ static void unix_walk_scc(void)
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unix_graph_grouped = true;
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}
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static void unix_walk_scc_fast(void)
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static void unix_walk_scc_fast(struct sk_buff_head *hitlist)
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{
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while (!list_empty(&unix_unvisited_vertices)) {
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struct unix_vertex *vertex;
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@ -480,263 +529,40 @@ static void unix_walk_scc_fast(void)
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scc_dead = unix_vertex_dead(vertex);
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}
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if (scc_dead)
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unix_collect_skb(&scc, hitlist);
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list_del(&scc);
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}
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list_replace_init(&unix_visited_vertices, &unix_unvisited_vertices);
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}
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static LIST_HEAD(gc_candidates);
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static LIST_HEAD(gc_inflight_list);
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/* Keep the number of times in flight count for the file
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* descriptor if it is for an AF_UNIX socket.
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*/
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void unix_inflight(struct user_struct *user, struct file *filp)
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{
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struct unix_sock *u = unix_get_socket(filp);
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spin_lock(&unix_gc_lock);
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if (u) {
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if (!u->inflight) {
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WARN_ON_ONCE(!list_empty(&u->link));
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list_add_tail(&u->link, &gc_inflight_list);
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} else {
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WARN_ON_ONCE(list_empty(&u->link));
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}
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u->inflight++;
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}
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spin_unlock(&unix_gc_lock);
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}
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void unix_notinflight(struct user_struct *user, struct file *filp)
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{
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struct unix_sock *u = unix_get_socket(filp);
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spin_lock(&unix_gc_lock);
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if (u) {
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WARN_ON_ONCE(!u->inflight);
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WARN_ON_ONCE(list_empty(&u->link));
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u->inflight--;
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if (!u->inflight)
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list_del_init(&u->link);
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}
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spin_unlock(&unix_gc_lock);
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}
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static void scan_inflight(struct sock *x, void (*func)(struct unix_sock *),
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struct sk_buff_head *hitlist)
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{
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struct sk_buff *skb;
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struct sk_buff *next;
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spin_lock(&x->sk_receive_queue.lock);
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skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
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/* Do we have file descriptors ? */
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if (UNIXCB(skb).fp) {
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bool hit = false;
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/* Process the descriptors of this socket */
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int nfd = UNIXCB(skb).fp->count;
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struct file **fp = UNIXCB(skb).fp->fp;
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while (nfd--) {
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/* Get the socket the fd matches if it indeed does so */
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struct unix_sock *u = unix_get_socket(*fp++);
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/* Ignore non-candidates, they could have been added
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* to the queues after starting the garbage collection
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*/
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if (u && test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
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hit = true;
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func(u);
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}
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}
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if (hit && hitlist != NULL) {
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__skb_unlink(skb, &x->sk_receive_queue);
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__skb_queue_tail(hitlist, skb);
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}
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}
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}
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spin_unlock(&x->sk_receive_queue.lock);
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}
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static void scan_children(struct sock *x, void (*func)(struct unix_sock *),
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struct sk_buff_head *hitlist)
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{
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if (x->sk_state != TCP_LISTEN) {
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scan_inflight(x, func, hitlist);
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} else {
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struct sk_buff *skb;
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struct sk_buff *next;
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struct unix_sock *u;
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LIST_HEAD(embryos);
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/* For a listening socket collect the queued embryos
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* and perform a scan on them as well.
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*/
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spin_lock(&x->sk_receive_queue.lock);
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skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
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u = unix_sk(skb->sk);
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/* An embryo cannot be in-flight, so it's safe
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* to use the list link.
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*/
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WARN_ON_ONCE(!list_empty(&u->link));
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list_add_tail(&u->link, &embryos);
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}
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spin_unlock(&x->sk_receive_queue.lock);
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while (!list_empty(&embryos)) {
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u = list_entry(embryos.next, struct unix_sock, link);
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scan_inflight(&u->sk, func, hitlist);
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list_del_init(&u->link);
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}
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}
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}
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static void dec_inflight(struct unix_sock *usk)
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{
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usk->inflight--;
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}
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static void inc_inflight(struct unix_sock *usk)
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{
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usk->inflight++;
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}
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static void inc_inflight_move_tail(struct unix_sock *u)
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{
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u->inflight++;
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/* If this still might be part of a cycle, move it to the end
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* of the list, so that it's checked even if it was already
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* passed over
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*/
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if (test_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags))
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list_move_tail(&u->link, &gc_candidates);
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}
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static bool gc_in_progress;
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static void __unix_gc(struct work_struct *work)
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{
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struct sk_buff_head hitlist;
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struct unix_sock *u, *next;
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LIST_HEAD(not_cycle_list);
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struct list_head cursor;
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spin_lock(&unix_gc_lock);
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if (!unix_graph_maybe_cyclic)
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if (!unix_graph_maybe_cyclic) {
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spin_unlock(&unix_gc_lock);
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goto skip_gc;
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}
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__skb_queue_head_init(&hitlist);
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if (unix_graph_grouped)
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unix_walk_scc_fast();
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unix_walk_scc_fast(&hitlist);
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else
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unix_walk_scc();
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/* First, select candidates for garbage collection. Only
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* in-flight sockets are considered, and from those only ones
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* which don't have any external reference.
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*
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* Holding unix_gc_lock will protect these candidates from
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* being detached, and hence from gaining an external
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* reference. Since there are no possible receivers, all
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* buffers currently on the candidates' queues stay there
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* during the garbage collection.
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*
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* We also know that no new candidate can be added onto the
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* receive queues. Other, non candidate sockets _can_ be
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* added to queue, so we must make sure only to touch
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* candidates.
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*/
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list_for_each_entry_safe(u, next, &gc_inflight_list, link) {
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long total_refs;
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total_refs = file_count(u->sk.sk_socket->file);
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WARN_ON_ONCE(!u->inflight);
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WARN_ON_ONCE(total_refs < u->inflight);
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if (total_refs == u->inflight) {
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list_move_tail(&u->link, &gc_candidates);
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__set_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
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__set_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
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}
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}
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/* Now remove all internal in-flight reference to children of
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* the candidates.
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*/
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list_for_each_entry(u, &gc_candidates, link)
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scan_children(&u->sk, dec_inflight, NULL);
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/* Restore the references for children of all candidates,
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* which have remaining references. Do this recursively, so
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* only those remain, which form cyclic references.
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*
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* Use a "cursor" link, to make the list traversal safe, even
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* though elements might be moved about.
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*/
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list_add(&cursor, &gc_candidates);
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while (cursor.next != &gc_candidates) {
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u = list_entry(cursor.next, struct unix_sock, link);
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/* Move cursor to after the current position. */
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list_move(&cursor, &u->link);
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if (u->inflight) {
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list_move_tail(&u->link, ¬_cycle_list);
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__clear_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
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scan_children(&u->sk, inc_inflight_move_tail, NULL);
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}
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}
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list_del(&cursor);
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/* Now gc_candidates contains only garbage. Restore original
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* inflight counters for these as well, and remove the skbuffs
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* which are creating the cycle(s).
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*/
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skb_queue_head_init(&hitlist);
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list_for_each_entry(u, &gc_candidates, link) {
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scan_children(&u->sk, inc_inflight, &hitlist);
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#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
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if (u->oob_skb) {
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kfree_skb(u->oob_skb);
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u->oob_skb = NULL;
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}
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#endif
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}
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/* not_cycle_list contains those sockets which do not make up a
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* cycle. Restore these to the inflight list.
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*/
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while (!list_empty(¬_cycle_list)) {
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u = list_entry(not_cycle_list.next, struct unix_sock, link);
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__clear_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
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list_move_tail(&u->link, &gc_inflight_list);
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}
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unix_walk_scc(&hitlist);
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spin_unlock(&unix_gc_lock);
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/* Here we are. Hitlist is filled. Die. */
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__skb_queue_purge(&hitlist);
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spin_lock(&unix_gc_lock);
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/* All candidates should have been detached by now. */
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WARN_ON_ONCE(!list_empty(&gc_candidates));
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skip_gc:
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/* Paired with READ_ONCE() in wait_for_unix_gc(). */
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WRITE_ONCE(gc_in_progress, false);
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spin_unlock(&unix_gc_lock);
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}
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static DECLARE_WORK(unix_gc_work, __unix_gc);
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