diff options
author | Mikulas Patocka <mpatocka@redhat.com> | 2014-01-06 23:01:22 -0500 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-02-13 13:48:01 -0800 |
commit | eef2b6df86323b5c9eaee154174afb1976741f38 (patch) | |
tree | 65bd724a740d630ead573d12dbb49e93f8536b6b /drivers/md/dm.c | |
parent | 025d61e0f163e55a7a7b08975640c5c75c2690b8 (diff) |
dm: wait until embedded kobject is released before destroying a device
commit be35f486108227e10fe5d96fd42fb2b344c59983 upstream.
There may be other parts of the kernel holding a reference on the dm
kobject. We must wait until all references are dropped before
deallocating the mapped_device structure.
The dm_kobject_release method signals that all references are dropped
via completion. But dm_kobject_release doesn't free the kobject (which
is embedded in the mapped_device structure).
This is the sequence of operations:
* when destroying a DM device, call kobject_put from dm_sysfs_exit
* wait until all users stop using the kobject, when it happens the
release method is called
* the release method signals the completion and should return without
delay
* the dm device removal code that waits on the completion continues
* the dm device removal code drops the dm_mod reference the device had
* the dm device removal code frees the mapped_device structure that
contains the kobject
Using kobject this way should avoid the module unload race that was
mentioned at the beginning of this thread:
https://lkml.org/lkml/2014/1/4/83
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/md/dm.c')
-rw-r--r-- | drivers/md/dm.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 1c13071a81b..d2523fedca3 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -187,6 +187,9 @@ struct mapped_device { /* sysfs handle */ struct kobject kobj; + /* wait until the kobject is released */ + struct completion kobj_completion; + /* zero-length flush that will be cloned and submitted to targets */ struct bio flush_bio; }; @@ -1904,6 +1907,7 @@ static struct mapped_device *alloc_dev(int minor) init_waitqueue_head(&md->wait); INIT_WORK(&md->work, dm_wq_work); init_waitqueue_head(&md->eventq); + init_completion(&md->kobj_completion); md->disk->major = _major; md->disk->first_minor = minor; @@ -2758,6 +2762,13 @@ struct mapped_device *dm_get_from_kobject(struct kobject *kobj) return md; } +struct completion *dm_get_completion_from_kobject(struct kobject *kobj) +{ + struct mapped_device *md = container_of(kobj, struct mapped_device, kobj); + + return &md->kobj_completion; +} + int dm_suspended_md(struct mapped_device *md) { return test_bit(DMF_SUSPENDED, &md->flags); |