path: root/drivers/md/dm-sysfs.c
diff options
authorMikulas Patocka <mpatocka@redhat.com>2014-01-06 23:01:22 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-02-13 13:48:01 -0800
commiteef2b6df86323b5c9eaee154174afb1976741f38 (patch)
tree65bd724a740d630ead573d12dbb49e93f8536b6b /drivers/md/dm-sysfs.c
parent025d61e0f163e55a7a7b08975640c5c75c2690b8 (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-sysfs.c')
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/md/dm-sysfs.c b/drivers/md/dm-sysfs.c
index 84d2b91e4ef..e0cc5d6a9e4 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));