dm: merge max_hw_sector

Make sure dm honours max_hw_sectors of underlying devices

  We still have no firm testing evidence in support of this patch but
  believe it may help to resolve some bug reports.  - agk

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

2 files changed, 10 insertions, 0 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f3f952e347ed..47818d8249cb 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -99,6 +99,9 @@ static void combine_restrictions_low(struct io_restrictions *lhs,
         lhs->max_segment_size =
                 min_not_zero(lhs->max_segment_size, rhs->max_segment_size);
 
+        lhs->max_hw_sectors =
+                min_not_zero(lhs->max_hw_sectors, rhs->max_hw_sectors);
+
         lhs->seg_boundary_mask =
                 min_not_zero(lhs->seg_boundary_mask, rhs->seg_boundary_mask);
 
@@ -566,6 +569,9 @@ void dm_set_device_limits(struct dm_target *ti, struct block_device *bdev)
         rs->max_segment_size =
                 min_not_zero(rs->max_segment_size, q->max_segment_size);
 
+        rs->max_hw_sectors =
+                min_not_zero(rs->max_hw_sectors, q->max_hw_sectors);
+
         rs->seg_boundary_mask =
                 min_not_zero(rs->seg_boundary_mask,
                              q->seg_boundary_mask);
@@ -703,6 +709,8 @@ static void check_for_valid_limits(struct io_restrictions *rs)
 {
         if (!rs->max_sectors)
                 rs->max_sectors = SAFE_MAX_SECTORS;
+        if (!rs->max_hw_sectors)
+                rs->max_hw_sectors = SAFE_MAX_SECTORS;
         if (!rs->max_phys_segments)
                 rs->max_phys_segments = MAX_PHYS_SEGMENTS;
         if (!rs->max_hw_segments)
@@ -901,6 +909,7 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
         q->max_hw_segments = t->limits.max_hw_segments;
         q->hardsect_size = t->limits.hardsect_size;
         q->max_segment_size = t->limits.max_segment_size;
+        q->max_hw_sectors = t->limits.max_hw_sectors;
         q->seg_boundary_mask = t->limits.seg_boundary_mask;
         q->bounce_pfn = t->limits.bounce_pfn;
         if (t->limits.no_cluster)
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index b8b7c51389fe..e765e191663d 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -115,6 +115,7 @@ struct io_restrictions {
         unsigned short          max_hw_segments;
         unsigned short          hardsect_size;
         unsigned int            max_segment_size;
+        unsigned int            max_hw_sectors;
         unsigned long           seg_boundary_mask;
         unsigned long           bounce_pfn;
         unsigned char           no_cluster; /* inverted so that 0 is default */