On Fri, Jun 01 2007, Neil Brown wrote: > On Friday June 1, dgc@xxxxxxx wrote: > > On Thu, May 31, 2007 at 02:31:21PM -0400, Phillip Susi wrote: > > > David Chinner wrote: > > > >That sounds like a good idea - we can leave the existing > > > >WRITE_BARRIER behaviour unchanged and introduce a new WRITE_ORDERED > > > >behaviour that only guarantees ordering. The filesystem can then > > > >choose which to use where appropriate.... > > > > > > So what if you want a synchronous write, but DON'T care about the order? > > > > submit_bio(WRITE_SYNC, bio); > > > > Already there, already used by XFS, JFS and direct I/O. > > Are you sure? > > You seem to be saying that WRITE_SYNC causes the write to be safe on > media before the request returns. That isn't my understanding. > I think (from comments near the definition and a quick grep through > the code) that WRITE_SYNC expedites the delivery of the request > through the elevator, but doesn't do anything special about getting it > onto the media. > It essentially say "Submit this request now, don't wait for more > request to bundle with it for better bandwidth utilisation" That is exactly right. WRITE_SYNC doesn't give any integrity guarentees, it's just makes sure it goes straight through the io scheduler. -- Jens Axboe -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
