Initial import

1 files changed, 566 insertions, 0 deletions

diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
new file mode 100644
index 000000000..ae964624e
--- /dev/null
+++ b/drivers/md/bcache/bset.h
@@ -0,0 +1,566 @@
+#ifndef _BCACHE_BSET_H
+#define _BCACHE_BSET_H
+
+#include <linux/bcache.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#include "util.h" /* for time_stats */
+
+/*
+ * 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, bch_ptr_invalid and
+ * bch_ptr_bad().
+ *
+ * bch_ptr_invalid() primarily filters out keys and pointers that would be
+ * invalid due to some sort of bug, whereas bch_ptr_bad() filters out keys and
+ * pointer that occur in normal practice but don't point to real data.
+ *
+ * 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.
+ */
+
+struct btree_keys;
+struct btree_iter;
+struct btree_iter_set;
+struct bkey_float;
+
+#define MAX_BSETS		4U
+
+struct bset_tree {
+	/*
+	 * We construct a binary tree in an array as if the array
+	 * started at 1, so that things line up on the same cachelines
+	 * better: see comments in bset.c at cacheline_to_bkey() for
+	 * details
+	 */
+
+	/* size of the binary tree and prev array */
+	unsigned		size;
+
+	/* function of size - precalculated for to_inorder() */
+	unsigned		extra;
+
+	/* copy of the last key in the set */
+	struct bkey		end;
+	struct bkey_float	*tree;
+
+	/*
+	 * The nodes in the bset tree point to specific keys - this
+	 * array holds the sizes of the previous key.
+	 *
+	 * Conceptually it's a member of struct bkey_float, but we want
+	 * to keep bkey_float to 4 bytes and prev isn't used in the fast
+	 * path.
+	 */
+	uint8_t			*prev;
+
+	/* The actual btree node, with pointers to each sorted set */
+	struct bset		*data;
+};
+
+struct btree_keys_ops {
+	bool		(*sort_cmp)(struct btree_iter_set,
+				    struct btree_iter_set);
+	struct bkey	*(*sort_fixup)(struct btree_iter *, struct bkey *);
+	bool		(*insert_fixup)(struct btree_keys *, struct bkey *,
+					struct btree_iter *, struct bkey *);
+	bool		(*key_invalid)(struct btree_keys *,
+				       const struct bkey *);
+	bool		(*key_bad)(struct btree_keys *, const struct bkey *);
+	bool		(*key_merge)(struct btree_keys *,
+				     struct bkey *, struct bkey *);
+	void		(*key_to_text)(char *, size_t, const struct bkey *);
+	void		(*key_dump)(struct btree_keys *, const struct bkey *);
+
+	/*
+	 * Only used for deciding whether to use START_KEY(k) or just the key
+	 * itself in a couple places
+	 */
+	bool		is_extents;
+};
+
+struct btree_keys {
+	const struct btree_keys_ops	*ops;
+	uint8_t			page_order;
+	uint8_t			nsets;
+	unsigned		last_set_unwritten:1;
+	bool			*expensive_debug_checks;
+
+	/*
+	 * Sets of sorted keys - the real btree node - plus a binary search tree
+	 *
+	 * set[0] is special; set[0]->tree, set[0]->prev and set[0]->data point
+	 * to the memory we have allocated for this btree node. Additionally,
+	 * set[0]->data points to the entire btree node as it exists on disk.
+	 */
+	struct bset_tree	set[MAX_BSETS];
+};
+
+static inline struct bset_tree *bset_tree_last(struct btree_keys *b)
+{
+	return b->set + b->nsets;
+}
+
+static inline bool bset_written(struct btree_keys *b, struct bset_tree *t)
+{
+	return t <= b->set + b->nsets - b->last_set_unwritten;
+}
+
+static inline bool bkey_written(struct btree_keys *b, struct bkey *k)
+{
+	return !b->last_set_unwritten || k < b->set[b->nsets].data->start;
+}
+
+static inline unsigned bset_byte_offset(struct btree_keys *b, struct bset *i)
+{
+	return ((size_t) i) - ((size_t) b->set->data);
+}
+
+static inline unsigned bset_sector_offset(struct btree_keys *b, struct bset *i)
+{
+	return bset_byte_offset(b, i) >> 9;
+}
+
+#define __set_bytes(i, k)	(sizeof(*(i)) + (k) * sizeof(uint64_t))
+#define set_bytes(i)		__set_bytes(i, i->keys)
+
+#define __set_blocks(i, k, block_bytes)				\
+	DIV_ROUND_UP(__set_bytes(i, k), block_bytes)
+#define set_blocks(i, block_bytes)				\
+	__set_blocks(i, (i)->keys, block_bytes)
+
+static inline size_t bch_btree_keys_u64s_remaining(struct btree_keys *b)
+{
+	struct bset_tree *t = bset_tree_last(b);
+
+	BUG_ON((PAGE_SIZE << b->page_order) <
+	       (bset_byte_offset(b, t->data) + set_bytes(t->data)));
+
+	if (!b->last_set_unwritten)
+		return 0;
+
+	return ((PAGE_SIZE << b->page_order) -
+		(bset_byte_offset(b, t->data) + set_bytes(t->data))) /
+		sizeof(u64);
+}
+
+static inline struct bset *bset_next_set(struct btree_keys *b,
+					 unsigned block_bytes)
+{
+	struct bset *i = bset_tree_last(b)->data;
+
+	return ((void *) i) + roundup(set_bytes(i), block_bytes);
+}
+
+void bch_btree_keys_free(struct btree_keys *);
+int bch_btree_keys_alloc(struct btree_keys *, unsigned, gfp_t);
+void bch_btree_keys_init(struct btree_keys *, const struct btree_keys_ops *,
+			 bool *);
+
+void bch_bset_init_next(struct btree_keys *, struct bset *, uint64_t);
+void bch_bset_build_written_tree(struct btree_keys *);
+void bch_bset_fix_invalidated_key(struct btree_keys *, struct bkey *);
+bool bch_bkey_try_merge(struct btree_keys *, struct bkey *, struct bkey *);
+void bch_bset_insert(struct btree_keys *, struct bkey *, struct bkey *);
+unsigned bch_btree_insert_key(struct btree_keys *, struct bkey *,
+			      struct bkey *);
+
+enum {
+	BTREE_INSERT_STATUS_NO_INSERT = 0,
+	BTREE_INSERT_STATUS_INSERT,
+	BTREE_INSERT_STATUS_BACK_MERGE,
+	BTREE_INSERT_STATUS_OVERWROTE,
+	BTREE_INSERT_STATUS_FRONT_MERGE,
+};
+
+/* Btree key iteration */
+
+struct btree_iter {
+	size_t size, used;
+#ifdef CONFIG_BCACHE_DEBUG
+	struct btree_keys *b;
+#endif
+	struct btree_iter_set {
+		struct bkey *k, *end;
+	} data[MAX_BSETS];
+};
+
+typedef bool (*ptr_filter_fn)(struct btree_keys *, const struct bkey *);
+
+struct bkey *bch_btree_iter_next(struct btree_iter *);
+struct bkey *bch_btree_iter_next_filter(struct btree_iter *,
+					struct btree_keys *, ptr_filter_fn);
+
+void bch_btree_iter_push(struct btree_iter *, struct bkey *, struct bkey *);
+struct bkey *bch_btree_iter_init(struct btree_keys *, struct btree_iter *,
+				 struct bkey *);
+
+struct bkey *__bch_bset_search(struct btree_keys *, struct bset_tree *,
+			       const struct bkey *);
+
+/*
+ * Returns the first key that is strictly greater than search
+ */
+static inline struct bkey *bch_bset_search(struct btree_keys *b,
+					   struct bset_tree *t,
+					   const struct bkey *search)
+{
+	return search ? __bch_bset_search(b, t, search) : t->data->start;
+}
+
+#define for_each_key_filter(b, k, iter, filter)				\
+	for (bch_btree_iter_init((b), (iter), NULL);			\
+	     ((k) = bch_btree_iter_next_filter((iter), (b), filter));)
+
+#define for_each_key(b, k, iter)					\
+	for (bch_btree_iter_init((b), (iter), NULL);			\
+	     ((k) = bch_btree_iter_next(iter));)
+
+/* Sorting */
+
+struct bset_sort_state {
+	mempool_t		*pool;
+
+	unsigned		page_order;
+	unsigned		crit_factor;
+
+	struct time_stats	time;
+};
+
+void bch_bset_sort_state_free(struct bset_sort_state *);
+int bch_bset_sort_state_init(struct bset_sort_state *, unsigned);
+void bch_btree_sort_lazy(struct btree_keys *, struct bset_sort_state *);
+void bch_btree_sort_into(struct btree_keys *, struct btree_keys *,
+			 struct bset_sort_state *);
+void bch_btree_sort_and_fix_extents(struct btree_keys *, struct btree_iter *,
+				    struct bset_sort_state *);
+void bch_btree_sort_partial(struct btree_keys *, unsigned,
+			    struct bset_sort_state *);
+
+static inline void bch_btree_sort(struct btree_keys *b,
+				  struct bset_sort_state *state)
+{
+	bch_btree_sort_partial(b, 0, state);
+}
+
+struct bset_stats {
+	size_t sets_written, sets_unwritten;
+	size_t bytes_written, bytes_unwritten;
+	size_t floats, failed;
+};
+
+void bch_btree_keys_stats(struct btree_keys *, struct bset_stats *);
+
+/* Bkey utility code */
+
+#define bset_bkey_last(i)	bkey_idx((struct bkey *) (i)->d, (i)->keys)
+
+static inline struct bkey *bset_bkey_idx(struct bset *i, unsigned idx)
+{
+	return bkey_idx(i->start, idx);
+}
+
+static inline void bkey_init(struct bkey *k)
+{
+	*k = ZERO_KEY;
+}
+
+static __always_inline int64_t bkey_cmp(const struct bkey *l,
+					const struct bkey *r)
+{
+	return unlikely(KEY_INODE(l) != KEY_INODE(r))
+		? (int64_t) KEY_INODE(l) - (int64_t) KEY_INODE(r)
+		: (int64_t) KEY_OFFSET(l) - (int64_t) KEY_OFFSET(r);
+}
+
+void bch_bkey_copy_single_ptr(struct bkey *, const struct bkey *,
+			      unsigned);
+bool __bch_cut_front(const struct bkey *, struct bkey *);
+bool __bch_cut_back(const struct bkey *, struct bkey *);
+
+static inline bool bch_cut_front(const struct bkey *where, struct bkey *k)
+{
+	BUG_ON(bkey_cmp(where, k) > 0);
+	return __bch_cut_front(where, k);
+}
+
+static inline bool bch_cut_back(const struct bkey *where, struct bkey *k)
+{
+	BUG_ON(bkey_cmp(where, &START_KEY(k)) < 0);
+	return __bch_cut_back(where, k);
+}
+
+#define PRECEDING_KEY(_k)					\
+({								\
+	struct bkey *_ret = NULL;				\
+								\
+	if (KEY_INODE(_k) || KEY_OFFSET(_k)) {			\
+		_ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0);	\
+								\
+		if (!_ret->low)					\
+			_ret->high--;				\
+		_ret->low--;					\
+	}							\
+								\
+	_ret;							\
+})
+
+static inline bool bch_ptr_invalid(struct btree_keys *b, const struct bkey *k)
+{
+	return b->ops->key_invalid(b, k);
+}
+
+static inline bool bch_ptr_bad(struct btree_keys *b, const struct bkey *k)
+{
+	return b->ops->key_bad(b, k);
+}
+
+static inline void bch_bkey_to_text(struct btree_keys *b, char *buf,
+				    size_t size, const struct bkey *k)
+{
+	return b->ops->key_to_text(buf, size, k);
+}
+
+static inline bool bch_bkey_equal_header(const struct bkey *l,
+					 const struct bkey *r)
+{
+	return (KEY_DIRTY(l) == KEY_DIRTY(r) &&
+		KEY_PTRS(l) == KEY_PTRS(r) &&
+		KEY_CSUM(l) == KEY_CSUM(r));
+}
+
+/* Keylists */
+
+struct keylist {
+	union {
+		struct bkey		*keys;
+		uint64_t		*keys_p;
+	};
+	union {
+		struct bkey		*top;
+		uint64_t		*top_p;
+	};
+
+	/* Enough room for btree_split's keys without realloc */
+#define KEYLIST_INLINE		16
+	uint64_t		inline_keys[KEYLIST_INLINE];
+};
+
+static inline void bch_keylist_init(struct keylist *l)
+{
+	l->top_p = l->keys_p = l->inline_keys;
+}
+
+static inline void bch_keylist_init_single(struct keylist *l, struct bkey *k)
+{
+	l->keys = k;
+	l->top = bkey_next(k);
+}
+
+static inline void bch_keylist_push(struct keylist *l)
+{
+	l->top = bkey_next(l->top);
+}
+
+static inline void bch_keylist_add(struct keylist *l, struct bkey *k)
+{
+	bkey_copy(l->top, k);
+	bch_keylist_push(l);
+}
+
+static inline bool bch_keylist_empty(struct keylist *l)
+{
+	return l->top == l->keys;
+}
+
+static inline void bch_keylist_reset(struct keylist *l)
+{
+	l->top = l->keys;
+}
+
+static inline void bch_keylist_free(struct keylist *l)
+{
+	if (l->keys_p != l->inline_keys)
+		kfree(l->keys_p);
+}
+
+static inline size_t bch_keylist_nkeys(struct keylist *l)
+{
+	return l->top_p - l->keys_p;
+}
+
+static inline size_t bch_keylist_bytes(struct keylist *l)
+{
+	return bch_keylist_nkeys(l) * sizeof(uint64_t);
+}
+
+struct bkey *bch_keylist_pop(struct keylist *);
+void bch_keylist_pop_front(struct keylist *);
+int __bch_keylist_realloc(struct keylist *, unsigned);
+
+/* Debug stuff */
+
+#ifdef CONFIG_BCACHE_DEBUG
+
+int __bch_count_data(struct btree_keys *);
+void __bch_check_keys(struct btree_keys *, const char *, ...);
+void bch_dump_bset(struct btree_keys *, struct bset *, unsigned);
+void bch_dump_bucket(struct btree_keys *);
+
+#else
+
+static inline int __bch_count_data(struct btree_keys *b) { return -1; }
+static inline void __bch_check_keys(struct btree_keys *b, const char *fmt, ...) {}
+static inline void bch_dump_bucket(struct btree_keys *b) {}
+void bch_dump_bset(struct btree_keys *, struct bset *, unsigned);
+
+#endif
+
+static inline bool btree_keys_expensive_checks(struct btree_keys *b)
+{
+#ifdef CONFIG_BCACHE_DEBUG
+	return *b->expensive_debug_checks;
+#else
+	return false;
+#endif
+}
+
+static inline int bch_count_data(struct btree_keys *b)
+{
+	return btree_keys_expensive_checks(b) ? __bch_count_data(b) : -1;
+}
+
+#define bch_check_keys(b, ...)						\
+do {									\
+	if (btree_keys_expensive_checks(b))				\
+		__bch_check_keys(b, __VA_ARGS__);			\
+} while (0)
+
+#endif