1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _BCACHEFS_BTREE_GC_H
3 #define _BCACHEFS_BTREE_GC_H
5 #include "btree_types.h"
7 int bch2_gc(struct bch_fs *, bool, bool);
8 int bch2_gc_gens(struct bch_fs *);
9 void bch2_gc_thread_stop(struct bch_fs *);
10 int bch2_gc_thread_start(struct bch_fs *);
13 * For concurrent mark and sweep (with other index updates), we define a total
14 * ordering of _all_ references GC walks:
16 * Note that some references will have the same GC position as others - e.g.
17 * everything within the same btree node; in those cases we're relying on
18 * whatever locking exists for where those references live, i.e. the write lock
21 * That locking is also required to ensure GC doesn't pass the updater in
22 * between the updater adding/removing the reference and updating the GC marks;
23 * without that, we would at best double count sometimes.
25 * That part is important - whenever calling bch2_mark_pointers(), a lock _must_
26 * be held that prevents GC from passing the position the updater is at.
28 * (What about the start of gc, when we're clearing all the marks? GC clears the
29 * mark with the gc pos seqlock held, and bch_mark_bucket checks against the gc
30 * position inside its cmpxchg loop, so crap magically works).
33 /* Position of (the start of) a gc phase: */
34 static inline struct gc_pos gc_phase(enum gc_phase phase)
36 return (struct gc_pos) {
43 static inline int gc_pos_cmp(struct gc_pos l, struct gc_pos r)
45 return cmp_int(l.phase, r.phase) ?:
46 bpos_cmp(l.pos, r.pos) ?:
47 cmp_int(l.level, r.level);
50 static inline enum gc_phase btree_id_to_gc_phase(enum btree_id id)
53 #define x(name, v) case BTREE_ID_##name: return GC_PHASE_BTREE_##name;
61 static inline struct gc_pos gc_pos_btree(enum btree_id id,
62 struct bpos pos, unsigned level)
64 return (struct gc_pos) {
65 .phase = btree_id_to_gc_phase(id),
72 * GC position of the pointers within a btree node: note, _not_ for &b->key
73 * itself, that lives in the parent node:
75 static inline struct gc_pos gc_pos_btree_node(struct btree *b)
77 return gc_pos_btree(b->c.btree_id, b->key.k.p, b->c.level);
81 * GC position of the pointer to a btree root: we don't use
82 * gc_pos_pointer_to_btree_node() here to avoid a potential race with
83 * btree_split() increasing the tree depth - the new root will have level > the
84 * old root and thus have a greater gc position than the old root, but that
85 * would be incorrect since once gc has marked the root it's not coming back.
87 static inline struct gc_pos gc_pos_btree_root(enum btree_id id)
89 return gc_pos_btree(id, SPOS_MAX, BTREE_MAX_DEPTH);
92 static inline bool gc_visited(struct bch_fs *c, struct gc_pos pos)
98 seq = read_seqcount_begin(&c->gc_pos_lock);
99 ret = gc_pos_cmp(pos, c->gc_pos) <= 0;
100 } while (read_seqcount_retry(&c->gc_pos_lock, seq));
105 static inline void bch2_do_gc_gens(struct bch_fs *c)
107 atomic_inc(&c->kick_gc);
109 wake_up_process(c->gc_thread);
112 #endif /* _BCACHEFS_BTREE_GC_H */