xen/blkfront: map REQ_FLUSH into a full barrier
Implement a flush as a full barrier, since we have nothing weaker.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 06e2812..3a318d8 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -245,14 +245,11 @@
}
/*
- * blkif_queue_request
+ * Generate a Xen blkfront IO request from a blk layer request. Reads
+ * and writes are handled as expected. Since we lack a loose flush
+ * request, we map flushes into a full ordered barrier.
*
- * request block io
- *
- * id: for guest use only.
- * operation: BLKIF_OP_{READ,WRITE,PROBE}
- * buffer: buffer to read/write into. this should be a
- * virtual address in the guest os.
+ * @req: a request struct
*/
static int blkif_queue_request(struct request *req)
{
@@ -289,7 +286,7 @@
ring_req->operation = rq_data_dir(req) ?
BLKIF_OP_WRITE : BLKIF_OP_READ;
- if (req->cmd_flags & REQ_HARDBARRIER)
+ if (req->cmd_flags & REQ_FLUSH)
ring_req->operation = BLKIF_OP_WRITE_BARRIER;
ring_req->nr_segments = blk_rq_map_sg(req->q, req, info->sg);
@@ -1069,14 +1066,8 @@
*/
info->feature_flush = 0;
- /*
- * The driver doesn't properly handled empty flushes, so
- * lets disable barrier support for now.
- */
-#if 0
if (!err && barrier)
info->feature_flush = REQ_FLUSH;
-#endif
err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);
if (err) {
