Hello, Jens. Jens Axboe wrote: > On Mon, May 28 2007, Neil Brown wrote: >> I think the implementation priorities here are: >> >> 1/ implement a zero-length BIO_RW_BARRIER option. >> 2/ Use it (or otherwise) to make all dm and md modules handle >> barriers (and loop?). >> 3/ Devise and implement appropriate fall-backs with-in the block layer >> so that -EOPNOTSUP is never returned. >> 4/ Remove unneeded cruft from filesystems (and elsewhere). > > This is the start of 1/ above. It's very lightly tested, it's verified > to DTRT here at least and not crash :-) > > It gets rid of the ->issue_flush_fn() queue callback, all the driver > knowledge resides in ->prepare_flush_fn() anyways. blkdev_issue_flush() > then just reuses the empty-bio approach to queue an empty barrier, this > should work equally well for stacked and non-stacked devices. > > While this patch isn't complete yet, it's clearly the right direction to > go. Finally took a brief look. :-) I think the sequencing for zero-length barrier can be better done by pre-setting QUEUE_ORDSEQ_BAR in start_ordered() rather than short circuiting the request after it's issued. What do you think? Thanks. -- tejun - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
