block: force an unlimited segment size on queues with a virt boundary

We currently fail to update the front/back segment size in the bio when deciding to allow an otherwise gappy segement to a device with a virt boundary. The reason why this did not cause problems is that devices with a virt boundary fundamentally don't use segments as we know it and thus don't care. Make that assumption formal by forcing an unlimited segement size in this case. Fixes: f6970f8 ("block: don't check if adjacent bvecs in one bio can be mergeable") Signed-off-by: Christoph Hellwig <[email protected]> Reviewed-by: Ming Lei <[email protected]> Reviewed-by: Hannes Reinecke <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
niw · May 23, 2019 · 09324d3 · 09324d3
1 parent eded341
commit 09324d3
Showing 1 changed file with 11 additions and 0 deletions.
diff --git a/block/blk-settings.c b/block/blk-settings.c
@@ -310,6 +310,9 @@ void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
 		       __func__, max_size);
 	}
 
+	/* see blk_queue_virt_boundary() for the explanation */
+	WARN_ON_ONCE(q->limits.virt_boundary_mask);
+
 	q->limits.max_segment_size = max_size;
 }
 EXPORT_SYMBOL(blk_queue_max_segment_size);
@@ -742,6 +745,14 @@ EXPORT_SYMBOL(blk_queue_segment_boundary);
 void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask)
 {
 	q->limits.virt_boundary_mask = mask;
+
+	/*
+	 * Devices that require a virtual boundary do not support scatter/gather
+	 * I/O natively, but instead require a descriptor list entry for each
+	 * 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;
 }
 EXPORT_SYMBOL(blk_queue_virt_boundary);