On 9 Apr 2019, at 14:46, Jens Axboe wrote: > On 4/9/19 12:42 PM, Chris Mason wrote: >> Looking at the patch, why is fsync special? Seems like you could add >> this ordering bit to any write? > > It's really not, the exact same technique could be used on any type of > command to imply ordering. My initial idea was to have an explicit > barrier/ordering command, but I didn't think that separating it from > an > actual command would be needed/useful. Might want to order discards? Commit a transaction to free some blocks, discard those blocks? > >> While you're here, do you want to add a way to FUA/cache flush? >> Basically the rest of what user land would need to make their own >> write-back-cache-safe implementation. > > FUA would be a WRITEV/WRITE_FIXED flag, that should be trivially > doable. > > In terms of cache flush, that's very heavy handed (and storage > oriented). What applications would want/need to do an explicit whole > device flush? Basically if someone is writing a userland filesystem they'd want to cache flush for the same reasons the kernel filesystems do. -chris
