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: f6970f83ef79 ("block: don't check if adjacent bvecs in one bio can be mergeable")
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
---
block/blk-settings.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 3facc41476be..2ae348c101a0 100644
--- 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);
--
2.20.1
