1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _BCACHEFS_BTREE_GC_H
3 #define _BCACHEFS_BTREE_GC_H
6 #include "btree_types.h"
8 int bch2_check_topology(struct bch_fs *);
9 int bch2_gc(struct bch_fs *, bool, bool);
10 int bch2_gc_gens(struct bch_fs *);
11 void bch2_gc_thread_stop(struct bch_fs *);
12 int bch2_gc_thread_start(struct bch_fs *);
15 * For concurrent mark and sweep (with other index updates), we define a total
16 * ordering of _all_ references GC walks:
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
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.
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.
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).
35 /* Position of (the start of) a gc phase: */
36 static inline struct gc_pos gc_phase(enum gc_phase phase)
38 return (struct gc_pos) {
45 static inline int gc_pos_cmp(struct gc_pos l, struct gc_pos r)
47 return cmp_int(l.phase, r.phase) ?:
48 bpos_cmp(l.pos, r.pos) ?:
49 cmp_int(l.level, r.level);
52 static inline enum gc_phase btree_id_to_gc_phase(enum btree_id id)
55 #define x(name, v, ...) case BTREE_ID_##name: return GC_PHASE_BTREE_##name;
63 static inline struct gc_pos gc_pos_btree(enum btree_id id,
64 struct bpos pos, unsigned level)
66 return (struct gc_pos) {
67 .phase = btree_id_to_gc_phase(id),
74 * GC position of the pointers within a btree node: note, _not_ for &b->key
75 * itself, that lives in the parent node:
77 static inline struct gc_pos gc_pos_btree_node(struct btree *b)
79 return gc_pos_btree(b->c.btree_id, b->key.k.p, b->c.level);
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.
89 static inline struct gc_pos gc_pos_btree_root(enum btree_id id)
91 return gc_pos_btree(id, SPOS_MAX, BTREE_MAX_DEPTH);
94 static inline bool gc_visited(struct bch_fs *c, struct gc_pos pos)
100 seq = read_seqcount_begin(&c->gc_pos_lock);
101 ret = gc_pos_cmp(pos, c->gc_pos) <= 0;
102 } while (read_seqcount_retry(&c->gc_pos_lock, seq));
107 static inline void bch2_do_gc_gens(struct bch_fs *c)
109 atomic_inc(&c->kick_gc);
111 wake_up_process(c->gc_thread);
114 #endif /* _BCACHEFS_BTREE_GC_H */