From Hugh

Instate Ingo's shmem_populate on top of the previous patches, now using
shmem_getpage(,,,SGP_QUICK) for the nonblocking case (its find_lock_page
may block, but rarely for long).  Note install_page will need redefining
if PAGE_CACHE_SIZE departs from PAGE_SIZE; note pgoff to populate must
be in terms of PAGE_SIZE; note page_cache_release if install_page fails.

filemap_populate similarly needs page_cache_release when install_page
fails, but filemap.c not included in this patch since we started out
from 2.5.43 rather than 2.5.43-mm2: whereas patches 1-8 could go
directly to 2.5.43, this 9/9 belongs with Ingo's population work.