btrfs: add more find_free_extent tracepoints

find_free_extent is a complicated function. It consists (at least) of:

- a hint that jumps into the middle of a for loop macro
- a middle loop trying every raid level
- an outer loop ascending through ffe loop levels
- complicated logic for skipping some of those ffe loop levels
- multiple underlying in-bg allocators (zoned, cluster, no cluster)

Which is all to say that more tracing is helpful for debugging its
behavior. Add two new tracepoints: at the entrance to the block_groups
loop (hit for every raid level and every ffe_ctl loop) and at the point
we seriously consider a block_group for allocation. This way we can see
the whole path through the algorithm, including hints, multiple loops,
etc.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.h b/fs/btrfs/extent-tree.h
index 64fa8ad7914a..daa5e3505886 100644
--- a/fs/btrfs/extent-tree.h
+++ b/fs/btrfs/extent-tree.h
@@ -76,6 +76,9 @@ struct find_free_extent_ctl {
 
 	/* Allocation policy */
 	enum btrfs_extent_allocation_policy policy;
+
+	/* Whether or not the allocator is currently following a hint */
+	bool hinted;
 };
 
 enum btrfs_inline_ref_type {