For BIO based DM, some targets aren't ready for dealing with
bigger incoming bio than 1Mbyte, such as crypt target.

Cc: Mike Snitzer <snit...@redhat.com>
Cc:dm-de...@redhat.com
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 drivers/md/dm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 2edbcc2d7d3f..631348699fb8 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -922,7 +922,16 @@ int dm_set_target_max_io_len(struct dm_target *ti, 
sector_t len)
                return -EINVAL;
        }
 
-       ti->max_io_len = (uint32_t) len;
+       /*
+        * BIO based queue uses its own splitting. When multipage bvecs
+        * is switched on, size of the incoming bio may be too big to
+        * be handled in some targets, such as crypt.
+        *
+        * When these targets are ready for the big bio, we can remove
+        * the limit.
+        */
+       ti->max_io_len = min_t(uint32_t, len,
+                              (BIO_MAX_PAGES * PAGE_SIZE));
 
        return 0;
 }
-- 
2.9.4

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