[dm-devel] [PATCH][RFC] dm: log writes target
Mike Snitzer
snitzer at redhat.com
Wed Feb 4 23:34:02 UTC 2015
On Wed, Feb 04 2015 at 1:41pm -0500,
Mike Snitzer <snitzer at redhat.com> wrote:
> @@ -527,9 +522,10 @@ static void normal_map_bio(struct dm_target *ti, struct bio *bio)
> struct log_writes_c *lc = ti->private;
>
> bio->bi_bdev = lc->dev->bdev;
> + // FIXME: why would bi_sector ever need to be changed?
> + // if you just copied dm-linear then it is misplaced since there isn't an offset
> if (bio_sectors(bio))
> - bio->bi_iter.bi_sector =
> - dm_target_offset(ti, bio->bi_iter.bi_sector);
> + bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);
> }
In above FIXME: s/misplaced/incomplete/
FYI sharing this quick private exchange I had with Alasdair just to make
sure I'm clear on what the above FIXME was trying to convey:
On Wed, Feb 04 2015 at 6:28pm -0500,
Mike Snitzer <snitzer at redhat.com> wrote:
> On Wed, Feb 04 2015 at 5:43pm -0500,
> Alasdair G Kergon <agk at redhat.com> wrote:
>
> > On Wed, Feb 04, 2015 at 01:41:09PM -0500, Mike Snitzer wrote:
> > > + // FIXME: why would bi_sector ever need to be changed?
> > > + // if you just copied dm-linear then it is misplaced since there isn't an offset
> >
> > Why shouldn't we use this target on the 2nd or later line of a
> table?
>
> Wasn't saying it shouldn't. Just was saying that Josef's target didn't
> go as far as say dm-linear with its 'start' offset. Without it then
> this dm-log-writes target implicitly assumes every logical address
> space, be it 2nd or later, identity maps to exact same offset on the
> backing the data disk.
>
> My FIXME was too cryptic. I can follow-up on this point.
More information about the dm-devel
mailing list