From be35f486108227e10fe5d96fd42fb2b344c59983 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Mon, 6 Jan 2014 23:01:22 -0500 Subject: 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 Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- drivers/md/dm.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/md/dm.h') diff --git a/drivers/md/dm.h b/drivers/md/dm.h index c57ba550f69e..1ab2028559ca 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -15,6 +15,7 @@ #include #include #include +#include #include "dm-stats.h" @@ -152,6 +153,7 @@ int dm_sysfs_init(struct mapped_device *md); void dm_sysfs_exit(struct mapped_device *md); struct kobject *dm_kobject(struct mapped_device *md); struct mapped_device *dm_get_from_kobject(struct kobject *kobj); +struct completion *dm_get_completion_from_kobject(struct kobject *kobj); /* * Targets for linear and striped mappings -- cgit v1.2.3