Title: #560: NSS: close files after mmap
@ChrisKowalczyk Hmm.. i thought we are using the fd in the memory cache operations, but
it does not seem to be the case, so yes we do not need the fd, just the pointer to the
mmaped region. Forget what I said and follow @simo5 's advice, sorry for confusion
@jhrozek Right that is also one of the possible reasons, sss_cache can mark the cache as
"recycled" and delete the file, the clients learn about this when they do next
request to the cache and reload the new file.
See the full comment at https://github.com/SSSD/sssd/pull/560#issuecomment-384601125