Allocating inodes from a single block

[Michael Nishimoto <miken@agami.com>]

Hi everyone,

Filesystem free space becomes fragmented over time.  It's possible
for total free space to be a decent size and still not have a chunk
large enough to allocate new inodes.

During testing, we managed to create a 111G filesystem which
could no longer create new inodes, but it had 6% free space.

Has anyone thought about how to solve this issue?

Ideally, a solution would still allocate multiple contiguous blocks
of inodes when space is available but would eventually work when
only single free blocks are available.  And it would be good if
any change remains backwards compatible with existing ondisk
formats.

thanks,

  Michael