On Wed, May 08, 2019 at 11:31:00PM -0400, Theodore Ts'o wrote: > On Thu, May 09, 2019 at 12:58:45PM +1000, Dave Chinner wrote: > > > > SOMC does not defining crash consistency rules - it defines change > > dependecies and how ordering and atomicity impact the dependency > > graph. How other people have interpreted that is out of my control. > > Fine; but it's a specific set of the crash consistency rules which I'm > objecting to; it's not a promise that I think I want to make. (And > before you blindly sign on the bottom line, I'd suggest that you read > it very carefully before deciding whether you want to agree to those > consistency rules as something that XFS will have honor forever. The > way I read it, it's goes beyond what you've articulated as SOMC.) I find myself (unusually) rooting for the status quo, where we /don't/ have a big SOMC rulebook that everyone has to follow, and instead we just tell people that if they really want to know a filesystem they had better try their workload with that fs + storage. If they don't like what they find, we have a reasonable amount of competition and niche specialization amongst the many filesystems that they can try the others, or if they're still unsatisfied, see if they can drive a consensus. Filesystems are like cars -- the basic interfaces are more or less the same and they but the implementations can still differ. (They also tend to crash, catch on fire, and leave a smear of destruction in their wake.) > > A new syscall with essentially the same user interface doesn't > > guarantee that these implementation problems will be solved. > > Well, it makes it easier to send all of the requests to the file > system in a single bundle. I'd also argue that it's simpler and > easier for an application to use a fsync2() interface as I sketched > out than trying to use the whole AIO or io_uring machinery. I *would* like to see a more concrete fsync2 proposal. And while I'm asking for ponies, whatever it is that came out of the DAX file flags discussion too. > > > So it's essentially identical to the AIO_FSYNC interface, except > > that it is synchronous. > > Pretty much, yes. OH yeah, I forgot we wired that up finally. > > Sheesh! Did LSFMM include a free lobotomy for participants, or > > something? "I'd rather have a bottle in front of me..." Peace out, see you all on the 20th! --D > Well, we missed your presence, alas. No doubt your attendance would > have improved the discussion. > > Cheers, > > - Ted
