On Tue, 13 Jan 2015, Jens Axboe wrote:
On 01/12/2015 11:35 AM, Keith Busch wrote:
On Mon, 12 Jan 2015, Keith Busch wrote:
Oh, let's look at "__blk_rq_prep_clone". dm calls that after
blk_get_request() for the blk-mq based multipath types and overrides the
destinations cmd_flags with the source's even though the source was not
allocated from a blk-mq based queue, much less a shared tag.
Untested patch. This will also preserve the failfast cmd_flag dm-mpath
set after allocating.
---
diff --git a/block/blk-core.c b/block/blk-core.c
index 7e78931..6201090 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2895,7 +2895,10 @@ EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
static void __blk_rq_prep_clone(struct request *dst, struct request *src)
{
dst->cpu = src->cpu;
- dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
+ if (dst->q->mq_ops)
+ dst->cmd_flags |= (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
+ else
+ dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
Making the two cases different is a bit... nonsensical. We should do this for
both cases, if safe, or move the MQ_INFLIGHT flag and expand the CLONE_MASK.
Expanding the clone mask won't do any good since the src doesn't come
from blk-mq and wouldn't ever have MQ_INFLIGHT set. Blk-mq initializes
the cmd_flags when you get one so I assumed OR'ing was safe. For the
non-blk-mq case, we have no guarantees how the req was initialized and
could have nonsense cmd_flags.
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