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

Signed-off-by: Ming Lei <tom.leim...@gmail.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 ef7bf1dd6900..ce454c6c1a4e 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -899,7 +899,16 @@ 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 and log write.
+        *
+        * When these targets are ready for the big bio, we can remove
+        * the limit.
+        */
+       ti->max_io_len = min_t(uint32_t, len,
+                              BIO_SP_MAX_SECTORS << SECTOR_SHIFT);
 
        return 0;
 }
-- 
2.7.4

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