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/extent_io.c b/fs/btrfs/extent_io.c
index 8bd1b40..563b2d1 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -914,6 +914,10 @@
}
EXPORT_SYMBOL(wait_on_extent_writeback);
+/*
+ * either insert or lock state struct between start and end use mask to tell
+ * us if waiting is desired.
+ */
int lock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask)
{
int err;
@@ -982,6 +986,13 @@
}
EXPORT_SYMBOL(set_range_writeback);
+/*
+ * find the first offset in the io tree with 'bits' set. zero is
+ * returned if we find something, and *start_ret and *end_ret are
+ * set to reflect the state struct that was found.
+ *
+ * If nothing was found, 1 is returned, < 0 on error
+ */
int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
u64 *start_ret, u64 *end_ret, int bits)
{
@@ -1017,6 +1028,10 @@
}
EXPORT_SYMBOL(find_first_extent_bit);
+/* find the first state struct with 'bits' set after 'start', and
+ * return it. tree->lock must be held. NULL will returned if
+ * nothing was found after 'start'
+ */
struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
u64 start, int bits)
{
@@ -1046,8 +1061,14 @@
}
EXPORT_SYMBOL(find_first_extent_bit_state);
-u64 find_lock_delalloc_range(struct extent_io_tree *tree,
- u64 *start, u64 *end, u64 max_bytes)
+/*
+ * find a contiguous range of bytes in the file marked as delalloc, not
+ * more than 'max_bytes'. start and end are used to return the range,
+ *
+ * 1 is returned if we find something, 0 if nothing was in the tree
+ */
+static noinline u64 find_lock_delalloc_range(struct extent_io_tree *tree,
+ u64 *start, u64 *end, u64 max_bytes)
{
struct rb_node *node;
struct extent_state *state;
@@ -1130,6 +1151,11 @@
return found;
}
+/*
+ * count the number of bytes in the tree that have a given bit(s)
+ * set. This can be fairly slow, except for EXTENT_DIRTY which is
+ * cached. The total number found is returned.
+ */
u64 count_range_bits(struct extent_io_tree *tree,
u64 *start, u64 search_end, u64 max_bytes,
unsigned long bits)
@@ -1245,6 +1271,10 @@
}
EXPORT_SYMBOL(unlock_range);
+/*
+ * set the private field for a given byte offset in the tree. If there isn't
+ * an extent_state there already, this does nothing.
+ */
int set_state_private(struct extent_io_tree *tree, u64 start, u64 private)
{
struct rb_node *node;