From 1aea2d2f968936eccaf57f3ff69d6a6a0bb5eb3e Mon Sep 17 00:00:00 2001
From: Zygo Blaxell <bees@furryterror.org>
Date: Mon, 3 Feb 2025 18:28:55 -0500
Subject: [PATCH] crawl: deprecate use of BeesCrawl to search the extent tree

BeesScanModeExtent can do that by itself now.  Overloading the subvol
crawl code resulted in an ugly, inefficient hack, and we definitely
don't want to accidentally continue to use it.

Remove the support for reading the extent tree and add some `assert`s
to make sure it isn't still used somewhere.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
---
 src/bees-roots.cc | 31 +++++++++++--------------------
 1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/src/bees-roots.cc b/src/bees-roots.cc
index 4623aeb..ae96342 100644
--- a/src/bees-roots.cc
+++ b/src/bees-roots.cc
@@ -2380,15 +2380,12 @@ BeesCrawl::fetch_extents()
 
 	// Don't set max_transid to m_max_transid here.	 See scan_one_ref.
 	m_btof.transid(old_state.m_min_transid);
+
+	// Deprecated: don't call this on the extent tree any more
+	assert(m_btof.tree() != BTRFS_EXTENT_TREE_OBJECTID);
+
 	if (catch_all([&]() {
 		m_next_extent_data = m_btof.lower_bound(old_state.m_objectid);
-		if (m_btof.tree() == BTRFS_EXTENT_TREE_OBJECTID) {
-			// Skip over TREE_BLOCK extent items, they don't have files
-			while (!!m_next_extent_data && (m_next_extent_data.extent_flags() & BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
-				BEESCOUNT(crawl_tree_block);
-				m_next_extent_data = m_btof.next(m_next_extent_data.objectid());
-			}
-		}
 	})) {
 		// Whoops that didn't work.  Stop scanning this subvol, move on to the next.
 		m_deferred = true;
@@ -2425,19 +2422,13 @@ BeesCrawl::bti_to_bfr(const BtrfsTreeItem &bti) const
 	if (!bti) {
 		return BeesFileRange();
 	}
-	if (bti.type() == BTRFS_EXTENT_ITEM_KEY) {
-		return BeesFileRange(
-			BeesFileId(get_state_end().m_root, bti.objectid()),
-			bti.objectid(),
-			bti.objectid() + bti.offset()
-		);
-	} else {
-		return BeesFileRange(
-			BeesFileId(get_state_end().m_root, bti.objectid()),
-			bti.offset(),
-			bti.offset() + bti.file_extent_logical_bytes()
-		);
-	}
+	// Deprecated: don't call peek_front() or pop_front() with extent tree any more
+	assert(bti.type() != BTRFS_EXTENT_ITEM_KEY);
+	return BeesFileRange(
+		BeesFileId(get_state_end().m_root, bti.objectid()),
+		bti.offset(),
+		bti.offset() + bti.file_extent_logical_bytes()
+	);
 }
 
 BeesFileRange