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, 13 insertions, 0 deletions

diff --git a/fs/xfs/xfs_buf_mem.c b/fs/xfs/xfs_buf_mem.c
index be71ba1a3d7b..73caa2ea8b18 100644
--- a/fs/xfs/xfs_buf_mem.c
+++ b/fs/xfs/xfs_buf_mem.c
@@ -187,3 +187,16 @@ xmbuf_unmap_page(
 	bp->b_pages = NULL;
 	bp->b_page_count = 0;
 }
+
+/* Is this a valid daddr within the buftarg? */
+bool
+xmbuf_verify_daddr(
+	struct xfs_buftarg	*btp,
+	xfs_daddr_t		daddr)
+{
+	struct inode		*inode = file_inode(btp->bt_file);
+
+	ASSERT(xfs_buftarg_is_mem(btp));
+
+	return daddr < (inode->i_sb->s_maxbytes >> BBSHIFT);
+}