% uname -a
SunOS ip-10-178-182-71.ec2.internal 5.11 omnios-d3950d8 i86pc i386 i86xpv)
posix_fallocate is detected by the configure script but fails at runtime (returns EINVAL) when invoked within __wt_allocate(). So far, I have observed this trying to create WT log files on both ZFS and tmpfs filesystems.
I was able to work around this issue by disabling HAVE_POSIX_FALLOCATE in wiredtiger_config.h after running configure but was wondering if there's a better way to fix this either when running configure or at runtime.