Commit ecdb2e257abc33ae6798d3ccba87bdafa40ef6b6
Committed by
Alasdair G Kergon
Alasdair G Kergon
1 parent
f7b934c812
Exists in
master
and in
7 other branches
dm table: remove dm_get from dm_table_get_md
Remove the dm_get() in dm_table_get_md() because dm_table_get_md() could be called from presuspend/postsuspend, which are called while mapped_device is in DMF_FREEING state, where dm_get() is not allowed. Justification for that is the lifetime of both objects: As far as the current dm design/implementation, mapped_device is never freed while targets are doing something, because dm core waits for targets to become quiet in dm_put() using presuspend/postsuspend. So targets should be able to touch mapped_device without holding reference count of the mapped_device, and we should allow targets to touch mapped_device even if it is in DMF_FREEING state. Backgrounds: I'm trying to remove the multipath internal queue, since dm core now has a generic queue for request-based dm. In the patch-set, the multipath target wants to request dm core to start/stop queue. One of such start/stop requests can happen during postsuspend() while the target waits for pg-init to complete, because the target stops queue when starting pg-init and tries to restart it when completing pg-init. Since queue belongs to mapped_device, it involves calling dm_table_get_md() and dm_put(). On the other hand, postsuspend() is called in dm_put() for mapped_device which is in DMF_FREEING state, and that triggers BUG_ON(DMF_FREEING) in the 2nd dm_put(). I had tried to solve this problem by changing only multipath not to touch mapped_device which is in DMF_FREEING state, but I couldn't and I came up with a question why we need dm_get() in dm_table_get_md(). Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Showing 3 changed files with 4 additions and 19 deletions Side-by-side Diff
drivers/md/dm-table.c
drivers/md/dm-uevent.c
| ... | ... | @@ -187,7 +187,7 @@ |
| 187 | 187 | |
| 188 | 188 | if (event_type >= ARRAY_SIZE(_dm_uevent_type_names)) { |
| 189 | 189 | DMERR("%s: Invalid event_type %d", __func__, event_type); |
| 190 | - goto out; | |
| 190 | + return; | |
| 191 | 191 | } |
| 192 | 192 | |
| 193 | 193 | event = dm_build_path_uevent(md, ti, |
| 194 | 194 | |
| ... | ... | @@ -195,12 +195,9 @@ |
| 195 | 195 | _dm_uevent_type_names[event_type].name, |
| 196 | 196 | path, nr_valid_paths); |
| 197 | 197 | if (IS_ERR(event)) |
| 198 | - goto out; | |
| 198 | + return; | |
| 199 | 199 | |
| 200 | 200 | dm_uevent_add(md, &event->elist); |
| 201 | - | |
| 202 | -out: | |
| 203 | - dm_put(md); | |
| 204 | 201 | } |
| 205 | 202 | EXPORT_SYMBOL_GPL(dm_path_uevent); |
| 206 | 203 |
drivers/md/dm.c
| ... | ... | @@ -2699,23 +2699,13 @@ |
| 2699 | 2699 | |
| 2700 | 2700 | int dm_suspended(struct dm_target *ti) |
| 2701 | 2701 | { |
| 2702 | - struct mapped_device *md = dm_table_get_md(ti->table); | |
| 2703 | - int r = dm_suspended_md(md); | |
| 2704 | - | |
| 2705 | - dm_put(md); | |
| 2706 | - | |
| 2707 | - return r; | |
| 2702 | + return dm_suspended_md(dm_table_get_md(ti->table)); | |
| 2708 | 2703 | } |
| 2709 | 2704 | EXPORT_SYMBOL_GPL(dm_suspended); |
| 2710 | 2705 | |
| 2711 | 2706 | int dm_noflush_suspending(struct dm_target *ti) |
| 2712 | 2707 | { |
| 2713 | - struct mapped_device *md = dm_table_get_md(ti->table); | |
| 2714 | - int r = __noflush_suspending(md); | |
| 2715 | - | |
| 2716 | - dm_put(md); | |
| 2717 | - | |
| 2718 | - return r; | |
| 2708 | + return __noflush_suspending(dm_table_get_md(ti->table)); | |
| 2719 | 2709 | } |
| 2720 | 2710 | EXPORT_SYMBOL_GPL(dm_noflush_suspending); |
| 2721 | 2711 |