On Tue, May 20 2008, Eric Sandeen wrote: > Jamie Lokier wrote: > > Theodore Tso wrote: > >> On Fri, May 16, 2008 at 02:09:56PM -0500, Eric Sandeen wrote: > >>> To ensure that bits are truly on-disk after an fsync, > >>> we should call blkdev_issue_flush if barriers are supported. > >> This patch isn't necessary, and in fact will cause a double flush. > >> When you call fsync(), it calls ext4_force_commit(), and we do a the > >> equivalent of a blkdev_issue_flush() today (which is what happenes > >> when you do a submit_bh(WRITE_BARRIER, bh), which is what setting > >> set_ordered_mode(bh) ends up causing. > > > > ISTR fsync() on ext3 did not always force a commit, if in-place data > > writes did not change any metadata. > > I think that might still be true, but I'm still looking through it (in > the background...) > > I tried blktrace to see what was going on but I'm not sure what an "NB" > in the RWBS field means, anyone know? Eric already knows this now, but for the benefit of anyone else that may be curious - it's an empty (data-less) barrier. 'N' is basically 'no data' (eg not a read nor a write) and 'B' is barrier. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
