On Mon, 29 Oct 2007 09:31:39 +0300
Vasily Averin <vvs@xxxxx> wrote:
> Device mapper uses its own bounce_pfn that may differ from one on underlying
> device. In that way dm can build incorrect requests that contain sg elements
> greater than underlying device is able to handle.
>
> This is the cause of slab corruption in i2o layer, occurred on i386 arch when
> very long direct IO requests are addressed to dm-over-i2o device.
>
> Signed-off-by: Vasily Averin <vvs@xxxxx>
>
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -102,6 +102,8 @@ static void combine_restrictions_low(struct io_restrictions
> lhs->seg_boundary_mask =
> min_not_zero(lhs->seg_boundary_mask, rhs->seg_boundary_mask);
>
> + lhs->bounce_pfn = min_not_zero(lhs->bounce_pfn, rhs->bounce_pfn);
> +
> lhs->no_cluster |= rhs->no_cluster;
> }
>
> @@ -566,6 +568,8 @@ void dm_set_device_limits(struct dm_target *ti, struct
> min_not_zero(rs->seg_boundary_mask,
> q->seg_boundary_mask);
>
> + rs->bounce_pfn = min_not_zero(rs->bounce_pfn, q->bounce_pfn);
> +
> rs->no_cluster |= !test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
> }
> EXPORT_SYMBOL_GPL(dm_set_device_limits);
> @@ -707,6 +711,8 @@ static void check_for_valid_limits(struct io_restrictions
> rs->max_segment_size = MAX_SEGMENT_SIZE;
> if (!rs->seg_boundary_mask)
> rs->seg_boundary_mask = -1;
> + if (!rs->bounce_pfn)
> + rs->bounce_pfn = -1;
> }
>
> int dm_table_add_target(struct dm_table *t, const char *type,
> @@ -891,6 +897,7 @@ void dm_table_set_restrictions(struct dm_table *t, struct
> q->hardsect_size = t->limits.hardsect_size;
> q->max_segment_size = t->limits.max_segment_size;
> q->seg_boundary_mask = t->limits.seg_boundary_mask;
> + q->bounce_pfn = t->limits.bounce_pfn;
> if (t->limits.no_cluster)
> q->queue_flags &= ~(1 << QUEUE_FLAG_CLUSTER);
> else
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -111,6 +111,7 @@ struct target_type {
>
> struct io_restrictions {
> unsigned long seg_boundary_mask;
> + unsigned long bounce_pfn;
> unsigned int max_sectors;
> unsigned int max_segment_size;
> unsigned short max_phys_segments;
Well that's a rather grave sounding bug. Two days and nobody from DM land
has commented? Hello?
I'll tag this as needed in 2.6.23.x as well.
I'll duck the "dm: struct io_restriction reordered" patch. People have
been changing things around in there and I had to fix a reject in "dm:
bounce_pfn limit added" to make it apply - let's not complicate life.
However it is a good change and hopefully the DM people will pick it up.
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