On Mon, Mar 27, 2017 at 06:59:44PM +0200, David Sterba wrote:
> On Fri, Mar 24, 2017 at 12:13:35PM -0700, Liu Bo wrote:
> > Now that scrub can fix data errors with the help of parity for raid56
> > profile, repair during read is able to as well.
> >
> > Although the mirror num in raid56 senario has different meanings, i.e.
>
> (typo: scenario)
>
Thanks!
> > 0 or 1: read data directly
> > > 1: do recover with parity,
> > it could be fit into how we repair bad block during read.
>
> Could we possibly add some symbolic names for the RAID56 case?
>
Yes, we could do that here, but I'm afraid it might not be helpful
because most of places still use mirror or mirror_num, such as
btrfs_submit_bio_hook and btrfs_map_bio.
> >
> > The trick is to use BTRFS_MAP_READ instead of BTRFS_MAP_WRITE to get the
> > device and position on it.
>
> Please also document the trick in the code before the following.
>
Good point.
Thanks,
-liubo
> > + if (btrfs_is_parity_mirror(map_tree, logical, length, mirror_num)) {
> > + /* use BTRFS_MAP_READ to get the phy dev and sector */
> > + ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, logical,
> > + &map_length, &bbio, 0);
> > + if (ret) {
> > + btrfs_bio_counter_dec(fs_info);
> > + bio_put(bio);
> > + return -EIO;
> > + }
> > + ASSERT(bbio->mirror_num == 1);
> > + } else {
> > + ret = btrfs_map_block(fs_info, BTRFS_MAP_WRITE, logical,
> > + &map_length, &bbio, mirror_num);
> > + if (ret) {
> > + btrfs_bio_counter_dec(fs_info);
> > + bio_put(bio);
> > + return -EIO;
> > + }
> > + BUG_ON(mirror_num != bbio->mirror_num);
> > }
> > - BUG_ON(mirror_num != bbio->mirror_num);
> > - sector = bbio->stripes[mirror_num-1].physical >> 9;
> > +
> > + sector = bbio->stripes[bbio->mirror_num - 1].physical >> 9;
> > bio->bi_iter.bi_sector = sector;
> > - dev = bbio->stripes[mirror_num-1].dev;
> > + dev = bbio->stripes[bbio->mirror_num - 1].dev;
> > btrfs_put_bbio(bbio);
> > if (!dev || !dev->bdev || !dev->writeable) {
> > btrfs_bio_counter_dec(fs_info);
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