[PATCH] dm mpath: manage reference on request queue of underlying devices

Mike Snitzer
2011-07-12T14:59:21Z

When processing a request, DM-mpath's map_io() set the cloned request's
request_queue to the appropriate underlying device's request_queue
without getting a reference on that request_queue.

DM-mpath now maintains a reference count on the underlying devices'
request_queue. This change wasn't motivated by a specific report but
code, like blk_insert_cloned_request(), will access the request_queue
with the understanding that the request_queue is valid.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm-mpath.c | 33 +++++++++++++++++++++------------
1 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index eadea8e..629efa3 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -161,11 +161,14 @@ static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
{
struct pgpath *pgpath, *tmp;
struct multipath *m = ti->private;
+ struct request_queue *q;

list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
list_del(&pgpath->list);
+ q = bdev_get_queue(pgpath->path.dev->bdev);
if (m->hw_handler_name)
- scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
+ scsi_dh_detach(q);
+ blk_put_queue(q);
dm_put_device(ti, pgpath->path.dev);
free_pgpath(pgpath);
}
@@ -552,6 +555,7 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
{
int r;
struct pgpath *p;
+ struct request_queue *q;
struct multipath *m = ti->private;

/* we need at least a path arg */
@@ -571,9 +575,14 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
goto bad;
}

- if (m->hw_handler_name) {
- struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
+ q = bdev_get_queue(p->path.dev->bdev);
+ r = blk_get_queue(q);
+ if (r) {
+ ti->error = "error getting request queue";
+ goto bad_queue;
+ }

+ if (m->hw_handler_name) {
r = scsi_dh_attach(q, m->hw_handler_name);
if (r == -EBUSY) {
/*
@@ -586,8 +595,7 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps

if (r < 0) {
ti->error = "error attaching hardware handler";
- dm_put_device(ti, p->path.dev);
- goto bad;
+ goto bad_finish;
}

if (m->hw_handler_params) {
@@ -596,21 +604,22 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
ti->error = "unable to set hardware "
"handler parameters";
scsi_dh_detach(q);
- dm_put_device(ti, p->path.dev);
- goto bad;
+ goto bad_finish;
}
}
}

r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
- if (r) {
- dm_put_device(ti, p->path.dev);
- goto bad;
- }
+ if (r)
+ goto bad_finish;

return p;

- bad:
+bad_finish:
+ blk_put_queue(q);
+bad_queue:
+ dm_put_device(ti, p->path.dev);
+bad:
free_pgpath(p);
return ERR_PTR(r);
}