diff options
author | Mikulas Patocka <mpatocka@redhat.com> | 2014-01-07 04:01:22 (GMT) |
---|---|---|
committer | Mike Snitzer <snitzer@redhat.com> | 2014-01-08 02:01:43 (GMT) |
commit | be35f486108227e10fe5d96fd42fb2b344c59983 (patch) | |
tree | 9cfaef139722da4118b4fcd906eb1196d9577b23 /drivers/md/dm-sysfs.c | |
parent | 1ddd641ddcfa46d719189468b6856e9b17381a61 (diff) | |
download | linux-be35f486108227e10fe5d96fd42fb2b344c59983.tar.xz |
dm: wait until embedded kobject is released before destroying a device
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>
Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/md/dm-sysfs.c')
-rw-r--r-- | drivers/md/dm-sysfs.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/md/dm-sysfs.c b/drivers/md/dm-sysfs.c index 84d2b91..e0cc5d6 100644 --- a/drivers/md/dm-sysfs.c +++ b/drivers/md/dm-sysfs.c @@ -79,6 +79,11 @@ static const struct sysfs_ops dm_sysfs_ops = { .show = dm_attr_show, }; +static void dm_kobject_release(struct kobject *kobj) +{ + complete(dm_get_completion_from_kobject(kobj)); +} + /* * dm kobject is embedded in mapped_device structure * no need to define release function here @@ -86,6 +91,7 @@ static const struct sysfs_ops dm_sysfs_ops = { static struct kobj_type dm_ktype = { .sysfs_ops = &dm_sysfs_ops, .default_attrs = dm_attrs, + .release = dm_kobject_release, }; /* @@ -104,5 +110,7 @@ int dm_sysfs_init(struct mapped_device *md) */ void dm_sysfs_exit(struct mapped_device *md) { - kobject_put(dm_kobject(md)); + struct kobject *kobj = dm_kobject(md); + kobject_put(kobj); + wait_for_completion(dm_get_completion_from_kobject(kobj)); } |