On Mon, 27 Apr 2009, Mikulas Patocka wrote:
>
>
> On Tue, 28 Apr 2009, Alasdair G Kergon wrote:
>
> > On Mon, Apr 27, 2009 at 07:32:00PM -0400, Mikulas Patocka wrote:
> > > On entry to the function it holds zero if it is processing zero-length
> > > barrier.
> >
> > OK - so that is a clear definition the writer of a target map function can
> > rely upon, good.
> >
> > > The line "bio->bi_sector = dc->start_write + (bio->bi_sector -
> > > ti->begin)" can set it to non-zero, so I set it to zero again. If you
> > > want, you can somehow rearrange the code so that "bio->bi_sector =
> > > dc->start_write + (bio->bi_sector - ti->begin)" is performed only if the
> > > request has non-zero length.
> >
> > Please do that. In dm I try to enforce a rule that the values of variables
> > always correspond to their definitions - if a calculation needs intermediate
> > steps then different and meaningful intermediate variables are used
> > instead. Here, bi_sector seems to be set to a meaningless intermediate
> > value which is a recipe for confusion.
>
> OK.
>
> Mikulas
Here it is:
Flush supoprt for dm-delay target.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/md/dm-delay.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Index: linux-2.6.30-rc2-devel/drivers/md/dm-delay.c
===================================================================
--- linux-2.6.30-rc2-devel.orig/drivers/md/dm-delay.c 2009-04-20 09:53:22.000000000 +0200
+++ linux-2.6.30-rc2-devel/drivers/md/dm-delay.c 2009-04-28 01:44:08.000000000 +0200
@@ -198,6 +198,7 @@ out:
mutex_init(&dc->timer_lock);
atomic_set(&dc->may_delay, 1);
+ ti->num_flush_requests = 1;
ti->private = dc;
return 0;
@@ -279,8 +280,9 @@ static int delay_map(struct dm_target *t
if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
bio->bi_bdev = dc->dev_write->bdev;
- bio->bi_sector = dc->start_write +
- (bio->bi_sector - ti->begin);
+ if (bio_sectors(bio))
+ bio->bi_sector = dc->start_write +
+ (bio->bi_sector - ti->begin);
return delay_bio(dc, dc->write_delay, bio);
}
--
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