If a single-queue dm device is stacked on top of multi-queue block
devices and map_tio_request() is called while there are no paths then
the request will be prepared for a single-queue path. If a path is
added after a request was prepared and before __multipath_map() is
called return DM_MAPIO_REQUEUE such that it gets unprepared and
reprepared as a blk-mq request.
Signed-off-by: Bart Van Assche <bart.vanass...@sandisk.com>
---
drivers/md/dm-mpath.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 7559537..6b20349 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -541,6 +541,7 @@ static int __multipath_map(struct dm_target *ti, struct
request *clone,
size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
struct pgpath *pgpath;
struct block_device *bdev;
+ struct request_queue *q;
struct dm_mpath_io *mpio;
/* Do we need to select a new pgpath? */
@@ -558,6 +559,18 @@ static int __multipath_map(struct dm_target *ti, struct
request *clone,
return r;
}
+ bdev = pgpath->path.dev->bdev;
+ q = bdev_get_queue(bdev);
+
+ /*
+ * When a request is prepared if there are no paths it may happen that
+ * the request was prepared for a single-queue path and that a
+ * multiqueue path is added before __multipath_map() is called. If
+ * that happens requeue to trigger unprepare and reprepare.
+ */
+ if ((clone && q->mq_ops) || (!clone && !q->mq_ops))
+ return r;
+
mpio = set_mpio(m, map_context);
if (!mpio)
/* ENOMEM, requeue */
@@ -566,22 +579,20 @@ static int __multipath_map(struct dm_target *ti, struct
request *clone,
mpio->pgpath = pgpath;
mpio->nr_bytes = nr_bytes;
- bdev = pgpath->path.dev->bdev;
-
if (clone) {
/*
* Old request-based interface: allocated clone is passed in.
* Used by: .request_fn stacked on .request_fn path(s).
*/
- clone->q = bdev_get_queue(bdev);
+ clone->q = q;
} else {
/*
* blk-mq request-based interface; used by both:
* .request_fn stacked on blk-mq path(s) and
* blk-mq stacked on blk-mq path(s).
*/
- clone = blk_mq_alloc_request(bdev_get_queue(bdev),
- rq_data_dir(rq), BLK_MQ_REQ_NOWAIT);
+ clone = blk_mq_alloc_request(q, rq_data_dir(rq),
+ BLK_MQ_REQ_NOWAIT);
if (IS_ERR(clone)) {
/* EBUSY, ENODEV or EWOULDBLOCK; requeue */
clear_request_fn_mpio(m, map_context);
--
2.10.1
--
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