[$] PostgreSQL visits LSFMM

The recent fsync() woesexperienced by PostgreSQL led to a session on the firstday (April 23) of the 2018 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). Those problemsalso led to a second-day session with PostgreSQL developer Andres Freund who gave anoverview of how PostgreSQL does I/O and where that ran aground on someassumptions that had been made. The session led to a fair amount ofdiscussion with the filesystem-track developers; real solutions seem to bein the offing.