btrfs: move leaf_data_end into ctree.c

This is only used in ctree.c, with the exception of zero'ing out extent
buffers we're getting ready to write out.  In theory we shouldn't have
an extent buffer with 0 items that we're writing out, however I'd rather
be safe than sorry so open code it in extent_io.c, and then copy the
helper into ctree.c.  This will make it easier to sync accessors.[ch]
into btrfs-progs, as this requires a helper that isn't defined in
accessors.h.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index f75e398d7b71..dc38c24a0ffa 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -51,6 +51,19 @@ static const struct btrfs_csums {
 				     .driver = "blake2b-256" },
 };
 
+/*
+ * The leaf data grows from end-to-front in the node.  this returns the address
+ * of the start of the last item, which is the stop of the leaf data stack.
+ */
+static unsigned int leaf_data_end(const struct extent_buffer *leaf)
+{
+	u32 nr = btrfs_header_nritems(leaf);
+
+	if (nr == 0)
+		return BTRFS_LEAF_DATA_SIZE(leaf->fs_info);
+	return btrfs_item_offset(leaf, nr - 1);
+}
+
 int btrfs_super_csum_size(const struct btrfs_super_block *s)
 {
 	u16 t = btrfs_super_csum_type(s);