Btrfs: add and improve comments

This improves the comments at the top of many functions.  It didn't
dive into the guts of functions because I was trying to
avoid merging problems with the new allocator and back reference work.

extent-tree.c and volumes.c were both skipped, and there is definitely
more work todo in cleaning and commenting the code.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/ref-cache.h b/fs/btrfs/ref-cache.h
index 617564787f52..16f3183d7c59 100644
--- a/fs/btrfs/ref-cache.h
+++ b/fs/btrfs/ref-cache.h
@@ -19,8 +19,11 @@
 #define __REFCACHE__
 
 struct btrfs_extent_info {
+        /* bytenr and num_bytes find the extent in the extent allocation tree */
         u64 bytenr;
         u64 num_bytes;
+
+        /* objectid and offset find the back reference for the file */
         u64 objectid;
         u64 offset;
 };