1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _BCACHEFS_BTREE_GC_H
3#define _BCACHEFS_BTREE_GC_H
4
5#include "bkey.h"
6#include "btree_types.h"
7
8int bch2_check_topology(struct bch_fs *);
9int bch2_gc(struct bch_fs *, bool, bool);
10int bch2_gc_gens(struct bch_fs *);
11void bch2_gc_thread_stop(struct bch_fs *);
12int bch2_gc_thread_start(struct bch_fs *);
13
14/*
15 * For concurrent mark and sweep (with other index updates), we define a total
16 * ordering of _all_ references GC walks:
17 *
18 * Note that some references will have the same GC position as others - e.g.
19 * everything within the same btree node; in those cases we're relying on
20 * whatever locking exists for where those references live, i.e. the write lock
21 * on a btree node.
22 *
23 * That locking is also required to ensure GC doesn't pass the updater in
24 * between the updater adding/removing the reference and updating the GC marks;
25 * without that, we would at best double count sometimes.
26 *
27 * That part is important - whenever calling bch2_mark_pointers(), a lock _must_
28 * be held that prevents GC from passing the position the updater is at.
29 *
30 * (What about the start of gc, when we're clearing all the marks? GC clears the
31 * mark with the gc pos seqlock held, and bch_mark_bucket checks against the gc
32 * position inside its cmpxchg loop, so crap magically works).
33 */
34
35/* Position of (the start of) a gc phase: */
36static inline struct gc_pos gc_phase(enum gc_phase phase)
37{
38 return (struct gc_pos) {
39 .phase = phase,
40 .pos = POS_MIN,
41 .level = 0,
42 };
43}
44
45static inline int gc_pos_cmp(struct gc_pos l, struct gc_pos r)
46{
47 return cmp_int(l.phase, r.phase) ?:
48 bpos_cmp(l: l.pos, r: r.pos) ?:
49 cmp_int(l.level, r.level);
50}
51
52static inline enum gc_phase btree_id_to_gc_phase(enum btree_id id)
53{
54 switch (id) {
55#define x(name, v, ...) case BTREE_ID_##name: return GC_PHASE_BTREE_##name;
56 BCH_BTREE_IDS()
57#undef x
58 default:
59 BUG();
60 }
61}
62
63static inline struct gc_pos gc_pos_btree(enum btree_id id,
64 struct bpos pos, unsigned level)
65{
66 return (struct gc_pos) {
67 .phase = btree_id_to_gc_phase(id),
68 .pos = pos,
69 .level = level,
70 };
71}
72
73/*
74 * GC position of the pointers within a btree node: note, _not_ for &b->key
75 * itself, that lives in the parent node:
76 */
77static inline struct gc_pos gc_pos_btree_node(struct btree *b)
78{
79 return gc_pos_btree(id: b->c.btree_id, pos: b->key.k.p, level: b->c.level);
80}
81
82/*
83 * GC position of the pointer to a btree root: we don't use
84 * gc_pos_pointer_to_btree_node() here to avoid a potential race with
85 * btree_split() increasing the tree depth - the new root will have level > the
86 * old root and thus have a greater gc position than the old root, but that
87 * would be incorrect since once gc has marked the root it's not coming back.
88 */
89static inline struct gc_pos gc_pos_btree_root(enum btree_id id)
90{
91 return gc_pos_btree(id, SPOS_MAX, BTREE_MAX_DEPTH);
92}
93
94static inline bool gc_visited(struct bch_fs *c, struct gc_pos pos)
95{
96 unsigned seq;
97 bool ret;
98
99 do {
100 seq = read_seqcount_begin(&c->gc_pos_lock);
101 ret = gc_pos_cmp(l: pos, r: c->gc_pos) <= 0;
102 } while (read_seqcount_retry(&c->gc_pos_lock, seq));
103
104 return ret;
105}
106
107static inline void bch2_do_gc_gens(struct bch_fs *c)
108{
109 atomic_inc(v: &c->kick_gc);
110 if (c->gc_thread)
111 wake_up_process(tsk: c->gc_thread);
112}
113
114#endif /* _BCACHEFS_BTREE_GC_H */
115

source code of linux/fs/bcachefs/btree_gc.h