The patch https://review.whamcloud.com/43989 "LU-14825 lod: pool spilling" implemented pool spilling functionality, so that files with uninitialized layouts referencing pool "X" can be redirected to use pool "Y" for OST object creation if pool "X" is (nearly) full. That avoids premature ENOSPC errors when e.g. a flash pool is full but the HDD pool is not, and the draining of the flash pool is not sufficient to keep up with new file creation.

The pool spilling functionality is similar to the "Self-Extending Layouts" functionality on a single file layout, but extended to affect all new file creations instead of only files with the specific SEL layout set.