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authorKiyoshi Ueda <k-ueda@ct.jp.nec.com>2010-03-06 02:29:52 +0000
committerAlasdair G Kergon <agk@redhat.com>2010-03-06 02:29:52 +0000
commitecdb2e257abc33ae6798d3ccba87bdafa40ef6b6 (patch)
tree497db6a95a9f06270506f6a75354d5df855d5a66 /drivers/md/dm.c
parentf7b934c8127deebf4eb56fbe4a4ae0da16b6dbcd (diff)
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/dm.c')
-rw-r--r--drivers/md/dm.c14
1 files changed, 2 insertions, 12 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index aa4e2aa86d4..21222f5193f 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);