dm: allocate requests in target when stacking on blk-mq devices
For blk-mq request-based DM the responsibility of allocating a cloned
request is transfered from DM core to the target type. Doing so
enables the cloned request to be allocated from the appropriate
blk-mq request_queue's pool (only the DM target, e.g. multipath, can
know which block device to send a given cloned request to).
Care was taken to preserve compatibility with old-style block request
completion that requires request-based DM _not_ acquire the clone
request's queue lock in the completion path. As such, there are now 2
different request-based DM target_type interfaces:
1) the original .map_rq() interface will continue to be used for
non-blk-mq devices -- the preallocated clone request is passed in
from DM core.
2) a new .clone_and_map_rq() and .release_clone_rq() will be used for
blk-mq devices -- blk_get_request() and blk_put_request() are used
respectively from these hooks.
dm_table_set_type() was updated to detect if the request-based target is
being stacked on blk-mq devices, if so DM_TYPE_MQ_REQUEST_BASED is set.
DM core disallows switching the DM table's type after it is set. This
means that there is no mixing of non-blk-mq and blk-mq devices within
the same request-based DM table.
[This patch was started by Keith and later heavily modified by Mike]
Tested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 2552b88..863fc8c 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -11,6 +11,7 @@
#include "dm-path-selector.h"
#include "dm-uevent.h"
+#include <linux/blkdev.h>
#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/mempool.h>
@@ -378,12 +379,13 @@
/*
* Map cloned requests
*/
-static int multipath_map(struct dm_target *ti, struct request *clone,
- union map_info *map_context)
+static int __multipath_map(struct dm_target *ti, struct request *clone,
+ union map_info *map_context,
+ struct request *rq, struct request **__clone)
{
struct multipath *m = (struct multipath *) ti->private;
int r = DM_MAPIO_REQUEUE;
- size_t nr_bytes = blk_rq_bytes(clone);
+ size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
struct pgpath *pgpath;
struct block_device *bdev;
struct dm_mpath_io *mpio;
@@ -416,12 +418,25 @@
bdev = pgpath->path.dev->bdev;
- clone->q = bdev_get_queue(bdev);
- clone->rq_disk = bdev->bd_disk;
- clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
-
spin_unlock_irq(&m->lock);
+ if (clone) {
+ /* Old request-based interface: allocated clone is passed in */
+ clone->q = bdev_get_queue(bdev);
+ clone->rq_disk = bdev->bd_disk;
+ clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
+ } else {
+ /* blk-mq request-based interface */
+ *__clone = blk_get_request(bdev_get_queue(bdev),
+ rq_data_dir(rq), GFP_KERNEL);
+ if (IS_ERR(*__clone))
+ /* ENOMEM, requeue */
+ return r;
+ (*__clone)->bio = (*__clone)->biotail = NULL;
+ (*__clone)->rq_disk = bdev->bd_disk;
+ (*__clone)->cmd_flags |= REQ_FAILFAST_TRANSPORT;
+ }
+
if (pgpath->pg->ps.type->start_io)
pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
&pgpath->path,
@@ -434,6 +449,24 @@
return r;
}
+static int multipath_map(struct dm_target *ti, struct request *clone,
+ union map_info *map_context)
+{
+ return __multipath_map(ti, clone, map_context, NULL, NULL);
+}
+
+static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
+ union map_info *map_context,
+ struct request **clone)
+{
+ return __multipath_map(ti, NULL, map_context, rq, clone);
+}
+
+static void multipath_release_clone(struct request *clone)
+{
+ blk_put_request(clone);
+}
+
/*
* If we run out of usable paths, should we queue I/O or error it?
*/
@@ -1670,11 +1703,13 @@
*---------------------------------------------------------------*/
static struct target_type multipath_target = {
.name = "multipath",
- .version = {1, 7, 0},
+ .version = {1, 8, 0},
.module = THIS_MODULE,
.ctr = multipath_ctr,
.dtr = multipath_dtr,
.map_rq = multipath_map,
+ .clone_and_map_rq = multipath_clone_and_map,
+ .release_clone_rq = multipath_release_clone,
.rq_end_io = multipath_end_io,
.presuspend = multipath_presuspend,
.postsuspend = multipath_postsuspend,