btrfs: remove BUG() after failure to insert delayed dir index item

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: remove BUG() after failure to insert delayed dir index item Instead of calling BUG() when we fail to insert a delayed dir index item into the delayed node's tree, we can just release all the resources we have allocated/acquired before and return the error to the caller. This is fine because all existing call chains undo anything they have done before calling btrfs_insert_delayed_dir_index() or BUG_ON (when creating pending snapshots in the transaction commit path). So remove the BUG() call and do proper error handling. This relates to a syzbot report linked below, but does not fix it because it only prevents hitting a BUG(), it does not fix the issue where somehow we attempt to use twice the same index number for different index items.

References

• https://git.kernel.org/stable/c/d10fd53393cc5de4b9cf1a4b8f9984f0a037aa51
• https://git.kernel.org/stable/c/2c58c3931ede7cd08cbecf1f1a4acaf0a04a41a9