btrfs-progs: Record highest inode number before repair.

btrfs-progs: Record highest inode number before repair.

Record highest inode number before inode repair.

This is especially important for corrupted leaf case.
Under that case, if use btrfs_find_free_objectid, it may find a ino
existing in corrupted leaf but dropped by btree_recover.
If that happens, created dir will be referenced incorrectly since there
may be inode_ref or dir_index/item refers to it.

So we must record the highest inode number according to the inode_cache.
Inode_cache is OK since when a inode_ref or dir_index/item is found even
the referenced source is not found, it will be created.
If we record the highest inode number of inode_cache, and use
highest_inode + 1 as 'lost+found' dir, it will ensure the newly created
dir not conflicting with any possible inode.

This provides the basis for nlink or inode rebuild for repairing btrfs
with leaf/node corruption.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>