[PATCH v1 1/3] block: Fix incorrect integrity sysfs reporting for DM devices

[Anuj gupta]

> > diff --git a/block/blk-settings.c b/block/blk-settings.c
> > index c44dadc35e1e..c32517c8bc2e 100644
> > --- a/block/blk-settings.c
> > +++ b/block/blk-settings.c
> > @@ -861,7 +861,8 @@ bool queue_limits_stack_integrity(struct queue_limits *t,
> >
> >       if (!ti->tuple_size) {
> >               /* inherit the settings from the first underlying device */
> > -             if (!(ti->flags & BLK_INTEGRITY_STACKED)) {
> > +             if (!(ti->flags & BLK_INTEGRITY_STACKED) &&
> > +                 (bi->flags & BLK_INTEGRITY_DEVICE_CAPABLE)) {
> >                       ti->flags = BLK_INTEGRITY_DEVICE_CAPABLE |
> >                               (bi->flags & BLK_INTEGRITY_REF_TAG);
> >                       ti->csum_type = bi->csum_type;
>
> Hmm.  I wonder if this is the correct logic.  Basically we do not want to
> allow mixing integrity capable and not integrity devices, do we?

It is about a situation where a non-integrity-capable device incorrectly
reports integrity capability due to improper flag propagation. The issue
is that BLK_INTEGRITY_DEVICE_CAPABLE is set incorrectly even when the
first underlying device does not support integrity. This part of the patch
tries to fix that.
For example, when I create a dm-linear device using an integrity-incapable
device, the resulting DM device wrongly reports integrity capability [1]

Rest of the handling in this patch would not be required once we correctly
initialize in blk_validate_integrity_limits as you suggested in the other
reply [2]

[1]
# cat /sys/block/nvme0n1/integrity/device_is_integrity_capable
0
# echo 0 409600 linear /dev/nvme0n1 0 > /tmp/table
# echo 409600 409600 linear /dev/nvme0n1 0 >> /tmp/table
# dmsetup create two /tmp/table
# cat /sys/block/dm-0/integrity/device_is_integrity_capable
1

[2]
https://lore.kernel.org/linux-block/20250225150753.GB6099@lst.de/

> So maybe the logic should be more something like:
>
>         if (!IS_ENABLED(CONFIG_BLK_DEV_INTEGRITY))
>                 return true;
>
>         if (ti->flags & BLK_INTEGRITY_STACKED) {
>                 /* check blk_integrity compatibility */
>         } else {
>                 ti->flags = BLK_INTEGRITY_STACKED;
>                 /* inherit blk_integrity, including the empty one  */
>         }
>