--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_BSET_H
+#define _BCACHEFS_BSET_H
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#include "bcachefs.h"
+#include "bkey.h"
+#include "bkey_methods.h"
+#include "btree_types.h"
+#include "util.h" /* for time_stats */
+#include "vstructs.h"
+
+/*
+ * BKEYS:
+ *
+ * A bkey contains a key, a size field, a variable number of pointers, and some
+ * ancillary flag bits.
+ *
+ * We use two different functions for validating bkeys, bkey_invalid and
+ * bkey_deleted().
+ *
+ * The one exception to the rule that ptr_invalid() filters out invalid keys is
+ * that it also filters out keys of size 0 - these are keys that have been
+ * completely overwritten. It'd be safe to delete these in memory while leaving
+ * them on disk, just unnecessary work - so we filter them out when resorting
+ * instead.
+ *
+ * We can't filter out stale keys when we're resorting, because garbage
+ * collection needs to find them to ensure bucket gens don't wrap around -
+ * unless we're rewriting the btree node those stale keys still exist on disk.
+ *
+ * We also implement functions here for removing some number of sectors from the
+ * front or the back of a bkey - this is mainly used for fixing overlapping
+ * extents, by removing the overlapping sectors from the older key.
+ *
+ * BSETS:
+ *
+ * A bset is an array of bkeys laid out contiguously in memory in sorted order,
+ * along with a header. A btree node is made up of a number of these, written at
+ * different times.
+ *
+ * There could be many of them on disk, but we never allow there to be more than
+ * 4 in memory - we lazily resort as needed.
+ *
+ * We implement code here for creating and maintaining auxiliary search trees
+ * (described below) for searching an individial bset, and on top of that we
+ * implement a btree iterator.
+ *
+ * BTREE ITERATOR:
+ *
+ * Most of the code in bcache doesn't care about an individual bset - it needs
+ * to search entire btree nodes and iterate over them in sorted order.
+ *
+ * The btree iterator code serves both functions; it iterates through the keys
+ * in a btree node in sorted order, starting from either keys after a specific
+ * point (if you pass it a search key) or the start of the btree node.
+ *
+ * AUXILIARY SEARCH TREES:
+ *
+ * Since keys are variable length, we can't use a binary search on a bset - we
+ * wouldn't be able to find the start of the next key. But binary searches are
+ * slow anyways, due to terrible cache behaviour; bcache originally used binary
+ * searches and that code topped out at under 50k lookups/second.
+ *
+ * So we need to construct some sort of lookup table. Since we only insert keys
+ * into the last (unwritten) set, most of the keys within a given btree node are
+ * usually in sets that are mostly constant. We use two different types of
+ * lookup tables to take advantage of this.
+ *
+ * Both lookup tables share in common that they don't index every key in the
+ * set; they index one key every BSET_CACHELINE bytes, and then a linear search
+ * is used for the rest.
+ *
+ * For sets that have been written to disk and are no longer being inserted
+ * into, we construct a binary search tree in an array - traversing a binary
+ * search tree in an array gives excellent locality of reference and is very
+ * fast, since both children of any node are adjacent to each other in memory
+ * (and their grandchildren, and great grandchildren...) - this means
+ * prefetching can be used to great effect.
+ *
+ * It's quite useful performance wise to keep these nodes small - not just
+ * because they're more likely to be in L2, but also because we can prefetch
+ * more nodes on a single cacheline and thus prefetch more iterations in advance
+ * when traversing this tree.
+ *
+ * Nodes in the auxiliary search tree must contain both a key to compare against
+ * (we don't want to fetch the key from the set, that would defeat the purpose),
+ * and a pointer to the key. We use a few tricks to compress both of these.
+ *
+ * To compress the pointer, we take advantage of the fact that one node in the
+ * search tree corresponds to precisely BSET_CACHELINE bytes in the set. We have
+ * a function (to_inorder()) that takes the index of a node in a binary tree and
+ * returns what its index would be in an inorder traversal, so we only have to
+ * store the low bits of the offset.
+ *
+ * The key is 84 bits (KEY_DEV + key->key, the offset on the device). To
+ * compress that, we take advantage of the fact that when we're traversing the
+ * search tree at every iteration we know that both our search key and the key
+ * we're looking for lie within some range - bounded by our previous
+ * comparisons. (We special case the start of a search so that this is true even
+ * at the root of the tree).
+ *
+ * So we know the key we're looking for is between a and b, and a and b don't
+ * differ higher than bit 50, we don't need to check anything higher than bit
+ * 50.
+ *
+ * We don't usually need the rest of the bits, either; we only need enough bits
+ * to partition the key range we're currently checking. Consider key n - the
+ * key our auxiliary search tree node corresponds to, and key p, the key
+ * immediately preceding n. The lowest bit we need to store in the auxiliary
+ * search tree is the highest bit that differs between n and p.
+ *
+ * Note that this could be bit 0 - we might sometimes need all 80 bits to do the
+ * comparison. But we'd really like our nodes in the auxiliary search tree to be
+ * of fixed size.
+ *
+ * The solution is to make them fixed size, and when we're constructing a node
+ * check if p and n differed in the bits we needed them to. If they don't we
+ * flag that node, and when doing lookups we fallback to comparing against the
+ * real key. As long as this doesn't happen to often (and it seems to reliably
+ * happen a bit less than 1% of the time), we win - even on failures, that key
+ * is then more likely to be in cache than if we were doing binary searches all
+ * the way, since we're touching so much less memory.
+ *
+ * The keys in the auxiliary search tree are stored in (software) floating
+ * point, with an exponent and a mantissa. The exponent needs to be big enough
+ * to address all the bits in the original key, but the number of bits in the
+ * mantissa is somewhat arbitrary; more bits just gets us fewer failures.
+ *
+ * We need 7 bits for the exponent and 3 bits for the key's offset (since keys
+ * are 8 byte aligned); using 22 bits for the mantissa means a node is 4 bytes.
+ * We need one node per 128 bytes in the btree node, which means the auxiliary
+ * search trees take up 3% as much memory as the btree itself.
+ *
+ * Constructing these auxiliary search trees is moderately expensive, and we
+ * don't want to be constantly rebuilding the search tree for the last set
+ * whenever we insert another key into it. For the unwritten set, we use a much
+ * simpler lookup table - it's just a flat array, so index i in the lookup table
+ * corresponds to the i range of BSET_CACHELINE bytes in the set. Indexing
+ * within each byte range works the same as with the auxiliary search trees.
+ *
+ * These are much easier to keep up to date when we insert a key - we do it
+ * somewhat lazily; when we shift a key up we usually just increment the pointer
+ * to it, only when it would overflow do we go to the trouble of finding the
+ * first key in that range of bytes again.
+ */
+
+enum bset_aux_tree_type {
+ BSET_NO_AUX_TREE,
+ BSET_RO_AUX_TREE,
+ BSET_RW_AUX_TREE,
+};
+
+#define BSET_TREE_NR_TYPES 3
+
+#define BSET_NO_AUX_TREE_VAL (U16_MAX)
+#define BSET_RW_AUX_TREE_VAL (U16_MAX - 1)
+
+static inline enum bset_aux_tree_type bset_aux_tree_type(const struct bset_tree *t)
+{
+ switch (t->extra) {
+ case BSET_NO_AUX_TREE_VAL:
+ EBUG_ON(t->size);
+ return BSET_NO_AUX_TREE;
+ case BSET_RW_AUX_TREE_VAL:
+ EBUG_ON(!t->size);
+ return BSET_RW_AUX_TREE;
+ default:
+ EBUG_ON(!t->size);
+ return BSET_RO_AUX_TREE;
+ }
+}
+
+/*
+ * BSET_CACHELINE was originally intended to match the hardware cacheline size -
+ * it used to be 64, but I realized the lookup code would touch slightly less
+ * memory if it was 128.
+ *
+ * It definites the number of bytes (in struct bset) per struct bkey_float in
+ * the auxiliar search tree - when we're done searching the bset_float tree we
+ * have this many bytes left that we do a linear search over.
+ *
+ * Since (after level 5) every level of the bset_tree is on a new cacheline,
+ * we're touching one fewer cacheline in the bset tree in exchange for one more
+ * cacheline in the linear search - but the linear search might stop before it
+ * gets to the second cacheline.
+ */
+
+#define BSET_CACHELINE 256
+
+static inline size_t btree_keys_cachelines(const struct btree *b)
+{
+ return (1U << b->byte_order) / BSET_CACHELINE;
+}
+
+static inline size_t btree_aux_data_bytes(const struct btree *b)
+{
+ return btree_keys_cachelines(b) * 8;
+}
+
+static inline size_t btree_aux_data_u64s(const struct btree *b)
+{
+ return btree_aux_data_bytes(b) / sizeof(u64);
+}
+
+#define for_each_bset(_b, _t) \
+ for (_t = (_b)->set; _t < (_b)->set + (_b)->nsets; _t++)
+
+#define bset_tree_for_each_key(_b, _t, _k) \
+ for (_k = btree_bkey_first(_b, _t); \
+ _k != btree_bkey_last(_b, _t); \
+ _k = bkey_p_next(_k))
+
+static inline bool bset_has_ro_aux_tree(const struct bset_tree *t)
+{
+ return bset_aux_tree_type(t) == BSET_RO_AUX_TREE;
+}
+
+static inline bool bset_has_rw_aux_tree(struct bset_tree *t)
+{
+ return bset_aux_tree_type(t) == BSET_RW_AUX_TREE;
+}
+
+static inline void bch2_bset_set_no_aux_tree(struct btree *b,
+ struct bset_tree *t)
+{
+ BUG_ON(t < b->set);
+
+ for (; t < b->set + ARRAY_SIZE(b->set); t++) {
+ t->size = 0;
+ t->extra = BSET_NO_AUX_TREE_VAL;
+ t->aux_data_offset = U16_MAX;
+ }
+}
+
+static inline void btree_node_set_format(struct btree *b,
+ struct bkey_format f)
+{
+ int len;
+
+ b->format = f;
+ b->nr_key_bits = bkey_format_key_bits(&f);
+
+ len = bch2_compile_bkey_format(&b->format, b->aux_data);
+ BUG_ON(len < 0 || len > U8_MAX);
+
+ b->unpack_fn_len = len;
+
+ bch2_bset_set_no_aux_tree(b, b->set);
+}
+
+static inline struct bset *bset_next_set(struct btree *b,
+ unsigned block_bytes)
+{
+ struct bset *i = btree_bset_last(b);
+
+ EBUG_ON(!is_power_of_2(block_bytes));
+
+ return ((void *) i) + round_up(vstruct_bytes(i), block_bytes);
+}
+
+void bch2_btree_keys_init(struct btree *);
+
+void bch2_bset_init_first(struct btree *, struct bset *);
+void bch2_bset_init_next(struct bch_fs *, struct btree *,
+ struct btree_node_entry *);
+void bch2_bset_build_aux_tree(struct btree *, struct bset_tree *, bool);
+
+void bch2_bset_insert(struct btree *, struct btree_node_iter *,
+ struct bkey_packed *, struct bkey_i *, unsigned);
+void bch2_bset_delete(struct btree *, struct bkey_packed *, unsigned);
+
+/* Bkey utility code */
+
+/* packed or unpacked */
+static inline int bkey_cmp_p_or_unp(const struct btree *b,
+ const struct bkey_packed *l,
+ const struct bkey_packed *r_packed,
+ const struct bpos *r)
+{
+ EBUG_ON(r_packed && !bkey_packed(r_packed));
+
+ if (unlikely(!bkey_packed(l)))
+ return bpos_cmp(packed_to_bkey_c(l)->p, *r);
+
+ if (likely(r_packed))
+ return __bch2_bkey_cmp_packed_format_checked(l, r_packed, b);
+
+ return __bch2_bkey_cmp_left_packed_format_checked(b, l, r);
+}
+
+static inline struct bset_tree *
+bch2_bkey_to_bset_inlined(struct btree *b, struct bkey_packed *k)
+{
+ unsigned offset = __btree_node_key_to_offset(b, k);
+ struct bset_tree *t;
+
+ for_each_bset(b, t)
+ if (offset <= t->end_offset) {
+ EBUG_ON(offset < btree_bkey_first_offset(t));
+ return t;
+ }
+
+ BUG();
+}
+
+struct bset_tree *bch2_bkey_to_bset(struct btree *, struct bkey_packed *);
+
+struct bkey_packed *bch2_bkey_prev_filter(struct btree *, struct bset_tree *,
+ struct bkey_packed *, unsigned);
+
+static inline struct bkey_packed *
+bch2_bkey_prev_all(struct btree *b, struct bset_tree *t, struct bkey_packed *k)
+{
+ return bch2_bkey_prev_filter(b, t, k, 0);
+}
+
+static inline struct bkey_packed *
+bch2_bkey_prev(struct btree *b, struct bset_tree *t, struct bkey_packed *k)
+{
+ return bch2_bkey_prev_filter(b, t, k, 1);
+}
+
+/* Btree key iteration */
+
+void bch2_btree_node_iter_push(struct btree_node_iter *, struct btree *,
+ const struct bkey_packed *,
+ const struct bkey_packed *);
+void bch2_btree_node_iter_init(struct btree_node_iter *, struct btree *,
+ struct bpos *);
+void bch2_btree_node_iter_init_from_start(struct btree_node_iter *,
+ struct btree *);
+struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *,
+ struct btree *,
+ struct bset_tree *);
+
+void bch2_btree_node_iter_sort(struct btree_node_iter *, struct btree *);
+void bch2_btree_node_iter_set_drop(struct btree_node_iter *,
+ struct btree_node_iter_set *);
+void bch2_btree_node_iter_advance(struct btree_node_iter *, struct btree *);
+
+#define btree_node_iter_for_each(_iter, _set) \
+ for (_set = (_iter)->data; \
+ _set < (_iter)->data + ARRAY_SIZE((_iter)->data) && \
+ (_set)->k != (_set)->end; \
+ _set++)
+
+static inline bool __btree_node_iter_set_end(struct btree_node_iter *iter,
+ unsigned i)
+{
+ return iter->data[i].k == iter->data[i].end;
+}
+
+static inline bool bch2_btree_node_iter_end(struct btree_node_iter *iter)
+{
+ return __btree_node_iter_set_end(iter, 0);
+}
+
+/*
+ * When keys compare equal, deleted keys compare first:
+ *
+ * XXX: only need to compare pointers for keys that are both within a
+ * btree_node_iterator - we need to break ties for prev() to work correctly
+ */
+static inline int bkey_iter_cmp(const struct btree *b,
+ const struct bkey_packed *l,
+ const struct bkey_packed *r)
+{
+ return bch2_bkey_cmp_packed(b, l, r)
+ ?: (int) bkey_deleted(r) - (int) bkey_deleted(l)
+ ?: cmp_int(l, r);
+}
+
+static inline int btree_node_iter_cmp(const struct btree *b,
+ struct btree_node_iter_set l,
+ struct btree_node_iter_set r)
+{
+ return bkey_iter_cmp(b,
+ __btree_node_offset_to_key(b, l.k),
+ __btree_node_offset_to_key(b, r.k));
+}
+
+/* These assume r (the search key) is not a deleted key: */
+static inline int bkey_iter_pos_cmp(const struct btree *b,
+ const struct bkey_packed *l,
+ const struct bpos *r)
+{
+ return bkey_cmp_left_packed(b, l, r)
+ ?: -((int) bkey_deleted(l));
+}
+
+static inline int bkey_iter_cmp_p_or_unp(const struct btree *b,
+ const struct bkey_packed *l,
+ const struct bkey_packed *r_packed,
+ const struct bpos *r)
+{
+ return bkey_cmp_p_or_unp(b, l, r_packed, r)
+ ?: -((int) bkey_deleted(l));
+}
+
+static inline struct bkey_packed *
+__bch2_btree_node_iter_peek_all(struct btree_node_iter *iter,
+ struct btree *b)
+{
+ return __btree_node_offset_to_key(b, iter->data->k);
+}
+
+static inline struct bkey_packed *
+bch2_btree_node_iter_peek_all(struct btree_node_iter *iter, struct btree *b)
+{
+ return !bch2_btree_node_iter_end(iter)
+ ? __btree_node_offset_to_key(b, iter->data->k)
+ : NULL;
+}
+
+static inline struct bkey_packed *
+bch2_btree_node_iter_peek(struct btree_node_iter *iter, struct btree *b)
+{
+ struct bkey_packed *k;
+
+ while ((k = bch2_btree_node_iter_peek_all(iter, b)) &&
+ bkey_deleted(k))
+ bch2_btree_node_iter_advance(iter, b);
+
+ return k;
+}
+
+static inline struct bkey_packed *
+bch2_btree_node_iter_next_all(struct btree_node_iter *iter, struct btree *b)
+{
+ struct bkey_packed *ret = bch2_btree_node_iter_peek_all(iter, b);
+
+ if (ret)
+ bch2_btree_node_iter_advance(iter, b);
+
+ return ret;
+}
+
+struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *,
+ struct btree *);
+struct bkey_packed *bch2_btree_node_iter_prev(struct btree_node_iter *,
+ struct btree *);
+
+struct bkey_s_c bch2_btree_node_iter_peek_unpack(struct btree_node_iter *,
+ struct btree *,
+ struct bkey *);
+
+#define for_each_btree_node_key(b, k, iter) \
+ for (bch2_btree_node_iter_init_from_start((iter), (b)); \
+ (k = bch2_btree_node_iter_peek((iter), (b))); \
+ bch2_btree_node_iter_advance(iter, b))
+
+#define for_each_btree_node_key_unpack(b, k, iter, unpacked) \
+ for (bch2_btree_node_iter_init_from_start((iter), (b)); \
+ (k = bch2_btree_node_iter_peek_unpack((iter), (b), (unpacked))).k;\
+ bch2_btree_node_iter_advance(iter, b))
+
+/* Accounting: */
+
+static inline void btree_keys_account_key(struct btree_nr_keys *n,
+ unsigned bset,
+ struct bkey_packed *k,
+ int sign)
+{
+ n->live_u64s += k->u64s * sign;
+ n->bset_u64s[bset] += k->u64s * sign;
+
+ if (bkey_packed(k))
+ n->packed_keys += sign;
+ else
+ n->unpacked_keys += sign;
+}
+
+static inline void btree_keys_account_val_delta(struct btree *b,
+ struct bkey_packed *k,
+ int delta)
+{
+ struct bset_tree *t = bch2_bkey_to_bset(b, k);
+
+ b->nr.live_u64s += delta;
+ b->nr.bset_u64s[t - b->set] += delta;
+}
+
+#define btree_keys_account_key_add(_nr, _bset_idx, _k) \
+ btree_keys_account_key(_nr, _bset_idx, _k, 1)
+#define btree_keys_account_key_drop(_nr, _bset_idx, _k) \
+ btree_keys_account_key(_nr, _bset_idx, _k, -1)
+
+#define btree_account_key_add(_b, _k) \
+ btree_keys_account_key(&(_b)->nr, \
+ bch2_bkey_to_bset(_b, _k) - (_b)->set, _k, 1)
+#define btree_account_key_drop(_b, _k) \
+ btree_keys_account_key(&(_b)->nr, \
+ bch2_bkey_to_bset(_b, _k) - (_b)->set, _k, -1)
+
+struct bset_stats {
+ struct {
+ size_t nr, bytes;
+ } sets[BSET_TREE_NR_TYPES];
+
+ size_t floats;
+ size_t failed;
+};
+
+void bch2_btree_keys_stats(const struct btree *, struct bset_stats *);
+void bch2_bfloat_to_text(struct printbuf *, struct btree *,
+ struct bkey_packed *);
+
+/* Debug stuff */
+
+void bch2_dump_bset(struct bch_fs *, struct btree *, struct bset *, unsigned);
+void bch2_dump_btree_node(struct bch_fs *, struct btree *);
+void bch2_dump_btree_node_iter(struct btree *, struct btree_node_iter *);
+
+#ifdef CONFIG_BCACHEFS_DEBUG
+
+void __bch2_verify_btree_nr_keys(struct btree *);
+void bch2_btree_node_iter_verify(struct btree_node_iter *, struct btree *);
+void bch2_verify_insert_pos(struct btree *, struct bkey_packed *,
+ struct bkey_packed *, unsigned);
+
+#else
+
+static inline void __bch2_verify_btree_nr_keys(struct btree *b) {}
+static inline void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
+ struct btree *b) {}
+static inline void bch2_verify_insert_pos(struct btree *b,
+ struct bkey_packed *where,
+ struct bkey_packed *insert,
+ unsigned clobber_u64s) {}
+#endif
+
+static inline void bch2_verify_btree_nr_keys(struct btree *b)
+{
+ if (bch2_debug_check_btree_accounting)
+ __bch2_verify_btree_nr_keys(b);
+}
+
+#endif /* _BCACHEFS_BSET_H */
projects / bcachefs-tools-debian / blobdiff