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, 2 insertions, 3 deletions

diff --git a/Documentation/filesystems/xfs/xfs-online-fsck-design.rst b/Documentation/filesystems/xfs/xfs-online-fsck-design.rst
index d03480266e9b..6333697ba3e8 100644
--- a/Documentation/filesystems/xfs/xfs-online-fsck-design.rst
+++ b/Documentation/filesystems/xfs/xfs-online-fsck-design.rst
@@ -2270,13 +2270,12 @@ follows:
    pointing to the xfile.
 
 3. Pass the buffer cache target, buffer ops, and other information to
-   ``xfbtree_create`` to write an initial tree header and root block to the
-   xfile.
+   ``xfbtree_init`` to initialize the passed in ``struct xfbtree`` and write an
+   initial root block to the xfile.
    Each btree type should define a wrapper that passes necessary arguments to
    the creation function.
    For example, rmap btrees define ``xfs_rmapbt_mem_create`` to take care of
    all the necessary details for callers.
-   A ``struct xfbtree`` object will be returned.
 
 4. Pass the xfbtree object to the btree cursor creation function for the
    btree type.