Hi, recursively listing a directory tree requires that you know which entries are directories so that you can recurse into them. The getdents() API can provide this information through the d_type field. Today, d_type is available if we use READDIRPLUS. A non-plus READDIR requests only the "rdattr_error" and "mounted_on_fileid" attributes, but not "type", and consequently sets d_type to DT_UNKNOWN. Requesting the "type" attribute for regular, non-plus READDIR would allow us to always return d_type, even for large directories where we switch to a non-plus READDIR. It would allow the user to recursively list directories of any size without the need for GETATTRs, and, if the server supports this, without any stat() or equivalent calls on the server. For some use cases, you could also mount with '-o nordirplus' to scan an entire file system efficiently. Since not all file servers may be able to produce the directory entry type efficiently, this could be implemented as a mount option that defaults off. Some local file systems offer a similar choice. For example, both ext4 and xfs have an (in this case mkfs-time) option to store the inode type in the directory. If this option is set, then getdents() always returns d_type. Would a patch that adds such a mount option be acceptable?
