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author | Kiyoshi Ueda <k-ueda@ct.jp.nec.com> | 2010-03-06 02:29:52 +0000 |
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committer | Alasdair G Kergon <agk@redhat.com> | 2010-03-06 02:29:52 +0000 |
commit | ecdb2e257abc33ae6798d3ccba87bdafa40ef6b6 (patch) | |
tree | 497db6a95a9f06270506f6a75354d5df855d5a66 /drivers/md | |
parent | f7b934c8127deebf4eb56fbe4a4ae0da16b6dbcd (diff) | |
download | blackbird-op-linux-ecdb2e257abc33ae6798d3ccba87bdafa40ef6b6.tar.gz blackbird-op-linux-ecdb2e257abc33ae6798d3ccba87bdafa40ef6b6.zip |
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>
Diffstat (limited to 'drivers/md')
-rw-r--r-- | drivers/md/dm-table.c | 2 | ||||
-rw-r--r-- | drivers/md/dm-uevent.c | 7 | ||||
-rw-r--r-- | drivers/md/dm.c | 14 |
3 files changed, 4 insertions, 19 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 4b22feb01a0c..7d70cca585ac 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -1231,8 +1231,6 @@ void dm_table_unplug_all(struct dm_table *t) struct mapped_device *dm_table_get_md(struct dm_table *t) { - dm_get(t->md); - return t->md; } diff --git a/drivers/md/dm-uevent.c b/drivers/md/dm-uevent.c index c7c555a8c7b2..6b1e3b61b25e 100644 --- a/drivers/md/dm-uevent.c +++ b/drivers/md/dm-uevent.c @@ -187,7 +187,7 @@ void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti, if (event_type >= ARRAY_SIZE(_dm_uevent_type_names)) { DMERR("%s: Invalid event_type %d", __func__, event_type); - goto out; + return; } event = dm_build_path_uevent(md, ti, @@ -195,12 +195,9 @@ void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti, _dm_uevent_type_names[event_type].name, path, nr_valid_paths); if (IS_ERR(event)) - goto out; + return; dm_uevent_add(md, &event->elist); - -out: - dm_put(md); } EXPORT_SYMBOL_GPL(dm_path_uevent); diff --git a/drivers/md/dm.c b/drivers/md/dm.c index aa4e2aa86d49..21222f5193fb 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2699,23 +2699,13 @@ int dm_suspended_md(struct mapped_device *md) int dm_suspended(struct dm_target *ti) { - struct mapped_device *md = dm_table_get_md(ti->table); - int r = dm_suspended_md(md); - - dm_put(md); - - return r; + return dm_suspended_md(dm_table_get_md(ti->table)); } EXPORT_SYMBOL_GPL(dm_suspended); int dm_noflush_suspending(struct dm_target *ti) { - struct mapped_device *md = dm_table_get_md(ti->table); - int r = __noflush_suspending(md); - - dm_put(md); - - return r; + return __noflush_suspending(dm_table_get_md(ti->table)); } EXPORT_SYMBOL_GPL(dm_noflush_suspending); |