[+cc Kent's new mail?] On Thu, 4 Jul 2013 10:53:37 +1000 NeilBrown <neilb@xxxxxxx> wrote: > > I would propose "bio_rewind" that exactly undoes any "bio_advance". > > [ ... snip ...] > > Then call that on pbio at the same place we call bio_reset on sbio. > > You could probably also call bio_rewind on sbio, and remove lots of that > code for setting the bio up again. This appears to work for my test case (no crashes or post repair mismatch_cnt): mdadm --fail /dev/$MD /dev/sda3 mdadm --remove /dev/$MD /dev/sda3 dd if=/dev/urandom of=/dev/$MD bs=1M count=500 mdadm --stop /dev/$MD mdadm --create /dev/$MD --level=1 --assume-clean --raid-devices=2 \ --bitmap=internal /dev/sda3 /dev/sdi3 echo repair > /sys/block/$MD/md/sync_action I'll reply to this email with the patches that implement your suggested changes. Feel free to combine or redo them, posting them here was the easiest way to provide my signed-off should you need it. Although it works, having to rewind the bio io_vec index (and clearing the bi_next pointers) before calling bio_copy_data feels a bit clunky. What bio_copy_data is really doing is "bio_copy_remaining_data in a bio chain," whereas MD wants "bio_copy_completed_data from a single bio". I took a look at Kent's tree and a lot of the block layer handling was simplified through the bvec_iter. I don't know if that code is destined for 3.11. If so, it would probably be easier to retest and base any MD changes off of his. And for 3.10 stable, the minimal fix would be for MD to just manipulate the bi_idx itself (or revert calling bio_copy_data altogether.) Regards, -- Joe -- 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
