Re: dm: don't overallocate the tags space

[Mike Snitzer <snitzer@redhat.com>]

On Fri, Feb 08 2019 at 10:58am -0500,
Bart Van Assche <bvanassche@acm.org> wrote:

> On Fri, 2019-02-08 at 10:52 -0500, Mikulas Patocka wrote:
> > bio_sectors returns the value in the units of 512-byte sectors (no matter
> > what's the real sector size of the device). dm-crypt multiplies
> > bio_sectors by on_disk_tag_size to calculate the space allocated for
> > integrity tags. If dm-crypt is running with sector size larger than 512,
> > it allocates more data than what's needed.
> > 
> > Device mapper trimmed this extra space when passing the bio to
> > dm-integrity, so this bug didn't result in any visible misbehavior. This
> > bug showed up when device mapper stopped trimming the bio.
> > 
> > Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> > Reported-by: Milan Broz <mbroz@redhat.com>
> 
> Hi Mikulas,
> 
> Is this a fix for commit fa8db4948f52 ("dm: don't use bio_trim() afterall")?
> If so, please consider adding a "Fixes:" tag.

No, it isn't.  It stands on its own.

But yes, it could serve as a replacement for fa8db4948f52 ("dm: don't
use bio_trim() afterall").  But using bio_trim() isn't critical, and I
intend to remove all of DM's internal bio splitting for 5.1 or later
anyway.