[PATCH] block: fix max segment size handling in blk_queue_virt_boundary

[Christoph Hellwig]

We should only set the max segment size to unlimited if we actually
have a virt boundary.  Otherwise we accidentally clear that limit
when called from the SCSI midlayer, which always calls
blk_queue_virt_boundary, even if that mask is 0.

Fixes: 7ad388d8e4c7 ("scsi: core: add a host / host template field for the virt 
boundary")
Reported-by: Guenter Roeck <li...@roeck-us.net>
Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 block/blk-settings.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 2ae348c101a0..2c1831207a8f 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -752,7 +752,8 @@ void blk_queue_virt_boundary(struct request_queue *q, 
unsigned long mask)
         * page (which might not be idential to the Linux PAGE_SIZE).  Because
         * of that they are not limited by our notion of "segment size".
         */
-       q->limits.max_segment_size = UINT_MAX;
+       if (mask)
+               q->limits.max_segment_size = UINT_MAX;
 }
 EXPORT_SYMBOL(blk_queue_virt_boundary);
 
-- 
2.20.1