bcachefs: Rework lru btree

This patch changes how the LRU index works:

Instead of using KEY_TYPE_lru where the bucket the lru entry points to
is part of the value, this switches to KEY_TYPE_set and encoding the
bucket we refer to in the low bits of the key.

This means that we no longer have to check for collisions when inserting
LRU entries. We'll be making using of this in the next patch, which adds
a btree write buffer - a pure write buffer for btree updates, where
updates are appended to a simple array and then periodically sorted and
batch inserted.

This is a new on disk format version, and a forced upgrade.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 23 insertions, 3 deletions

diff --git a/fs/bcachefs/lru.h b/fs/bcachefs/lru.h
index 925c29b49b86..2e22f139848a 100644
--- a/fs/bcachefs/lru.h
+++ b/fs/bcachefs/lru.h
@@ -2,6 +2,26 @@
 #ifndef _BCACHEFS_LRU_H
 #define _BCACHEFS_LRU_H
 
+#define LRU_TIME_BITS	48
+#define LRU_TIME_MAX	((1ULL << LRU_TIME_BITS) - 1)
+
+static inline struct bpos lru_pos(u16 lru_id, u64 dev_bucket, u64 time)
+{
+	EBUG_ON(time > LRU_TIME_MAX);
+
+	return POS(((u64) lru_id << LRU_TIME_BITS)|time, dev_bucket);
+}
+
+static inline u64 lru_pos_id(struct bpos pos)
+{
+	return pos.inode >> LRU_TIME_BITS;
+}
+
+static inline u64 lru_pos_time(struct bpos pos)
+{
+	return pos.inode & ~(~0ULL << LRU_TIME_BITS);
+}
+
 int bch2_lru_invalid(const struct bch_fs *, struct bkey_s_c, int, struct printbuf *);
 void bch2_lru_to_text(struct printbuf *, struct bch_fs *, struct bkey_s_c);
 
@@ -10,9 +30,9 @@ void bch2_lru_to_text(struct printbuf *, struct bch_fs *, struct bkey_s_c);
 	.val_to_text	= bch2_lru_to_text,	\
 })
 
-int bch2_lru_delete(struct btree_trans *, u64, u64, u64, struct bkey_s_c);
-int bch2_lru_set(struct btree_trans *, u64, u64, u64 *);
-int bch2_lru_change(struct btree_trans *, u64, u64, u64, u64 *, struct bkey_s_c);
+int bch2_lru_del(struct btree_trans *, u16, u64, u64);
+int bch2_lru_set(struct btree_trans *, u16, u64, u64);
+int bch2_lru_change(struct btree_trans *, u16, u64, u64, u64);
 
 int bch2_check_lrus(struct bch_fs *);