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>
diff --git a/fs/btrfs/ref-cache.c b/fs/btrfs/ref-cache.c
index 30fcb7a..a50ebb6 100644
--- a/fs/btrfs/ref-cache.c
+++ b/fs/btrfs/ref-cache.c
@@ -21,6 +21,16 @@
#include "ref-cache.h"
#include "transaction.h"
+/*
+ * leaf refs are used to cache the information about which extents
+ * a given leaf has references on. This allows us to process that leaf
+ * in btrfs_drop_snapshot without needing to read it back from disk.
+ */
+
+/*
+ * kmalloc a leaf reference struct and update the counters for the
+ * total ref cache size
+ */
struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
int nr_extents)
{
@@ -40,6 +50,10 @@
return ref;
}
+/*
+ * free a leaf reference struct and update the counters for the
+ * total ref cache size
+ */
void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
if (!ref)
@@ -135,6 +149,10 @@
return 0;
}
+/*
+ * find the leaf ref for a given extent. This returns the ref struct with
+ * a usage reference incremented
+ */
struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
u64 bytenr)
{
@@ -160,6 +178,10 @@
return NULL;
}
+/*
+ * add a fully filled in leaf ref struct
+ * remove all the refs older than a given root generation
+ */
int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
int shared)
{
@@ -184,6 +206,10 @@
return ret;
}
+/*
+ * remove a single leaf ref from the tree. This drops the ref held by the tree
+ * only
+ */
int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
struct btrfs_leaf_ref_tree *tree;