xfs: support in-memory btrees

Adapt the generic btree cursor code to be able to create a btree whose
buffers come from a (presumably in-memory) buftarg with a header block
that's specific to in-memory btrees.  We'll connect this to other parts
of online scrub in the next patches.

Note that in-memory btrees always have a block size matching the system
memory page size for efficiency reasons.  There are also a few things we
need to do to finalize a btree update; that's covered in the next patch.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 72 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_btree_mem.h b/fs/xfs/libxfs/xfs_btree_mem.h
new file mode 100644
index 000000000000..ecc2ceac3ed4
--- /dev/null
+++ b/fs/xfs/libxfs/xfs_btree_mem.h
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2021-2024 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#ifndef __XFS_BTREE_MEM_H__
+#define __XFS_BTREE_MEM_H__
+
+typedef uint64_t xfbno_t;
+
+#define XFBNO_BLOCKSIZE			(XMBUF_BLOCKSIZE)
+#define XFBNO_BBSHIFT			(XMBUF_BLOCKSHIFT - BBSHIFT)
+#define XFBNO_BBSIZE			(XFBNO_BLOCKSIZE >> BBSHIFT)
+
+static inline xfs_daddr_t xfbno_to_daddr(xfbno_t blkno)
+{
+	return blkno << XFBNO_BBSHIFT;
+}
+
+static inline xfbno_t xfs_daddr_to_xfbno(xfs_daddr_t daddr)
+{
+	return daddr >> XFBNO_BBSHIFT;
+}
+
+struct xfbtree {
+	/* buffer cache target for this in-memory btree */
+	struct xfs_buftarg		*target;
+
+	/* Highest block number that has been written to. */
+	xfbno_t				highest_bno;
+
+	/* Owner of this btree. */
+	unsigned long long		owner;
+
+	/* Btree header */
+	union xfs_btree_ptr		root;
+	unsigned int			nlevels;
+
+	/* Minimum and maximum records per block. */
+	unsigned int			maxrecs[2];
+	unsigned int			minrecs[2];
+};
+
+#ifdef CONFIG_XFS_BTREE_IN_MEM
+static inline bool xfbtree_verify_bno(struct xfbtree *xfbt, xfbno_t bno)
+{
+	return xmbuf_verify_daddr(xfbt->target, xfbno_to_daddr(bno));
+}
+
+void xfbtree_set_root(struct xfs_btree_cur *cur,
+		const union xfs_btree_ptr *ptr, int inc);
+void xfbtree_init_ptr_from_cur(struct xfs_btree_cur *cur,
+		union xfs_btree_ptr *ptr);
+struct xfs_btree_cur *xfbtree_dup_cursor(struct xfs_btree_cur *cur);
+
+int xfbtree_get_minrecs(struct xfs_btree_cur *cur, int level);
+int xfbtree_get_maxrecs(struct xfs_btree_cur *cur, int level);
+
+int xfbtree_alloc_block(struct xfs_btree_cur *cur,
+		const union xfs_btree_ptr *start, union xfs_btree_ptr *ptr,
+		int *stat);
+int xfbtree_free_block(struct xfs_btree_cur *cur, struct xfs_buf *bp);
+
+/* Callers must set xfbt->target and xfbt->owner before calling this */
+int xfbtree_init(struct xfs_mount *mp, struct xfbtree *xfbt,
+		struct xfs_buftarg *btp, const struct xfs_btree_ops *ops);
+void xfbtree_destroy(struct xfbtree *xfbt);
+#else
+# define xfbtree_verify_bno(...)	(false)
+#endif /* CONFIG_XFS_BTREE_IN_MEM */
+
+#endif /* __XFS_BTREE_MEM_H__ */