On Wed, 28 Jul 2010 11:28:59 +0200, Christoph Hellwig <hch@xxxxxx> wrote: > On Wed, Jul 28, 2010 at 11:17:06AM +0200, Tejun Heo wrote: > > I'll re-read barrier code and see how hard it would be to implement a > > proper solution. > > If we move all filesystems to non-draining barriers with pre- and post- > flushes that might actually be a relatively easy first step. We don't > have the complications to deal with multiple types of barriers to > start with, and it'll fix the issue for devices without volatile write > caches completely. > > I just need some help from the filesystem folks to determine if they > are safe with them. > > I know for sure that ext3 and xfs are from looking through them. And > I know reiserfs is if we make sure it doesn't hit the code path that > relies on it that is currently enabled by the barrier option. > > I'll just need more feedback from ext4, gfs2, btrfs and nilfs folks. With regard to nilfs, barrier is applied to writeback of super block since it saves position of a recent log and this log needs to be written to the platter prior to the super block. And so, I think a pre-flush + a FUA write can be used instead of draining for the barrier use in nilfs. Thanks, Ryusuke Konishi -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
