btrfs-progs: check, properly reset nlink of multi-linked file

btrfs-progs: check, properly reset nlink of multi-linked file

If a file is linked from more than one directory and only one
of the links is corrupted, btrfs check dose not reset the nlink
properly. Actually it can go into infinite loop to link the broken file
into lost+found.

This patch fix two part of the code. The first one delay the freeing
valid (no error, found inode ref, directory index, and directory
item) backrefs. Freeing valid backrefs earier prevent reset_nlink() to
add back all valid links.

The second fix is obvious: passing `ref_type' to btrfs_add_link() is just
wrong. It should be `filetype' instead. The current code can break all valid
file links.

Signed-off-by: Naohiro Aota <naota@elisp.net>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>