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authorMikulas Patocka <mpatocka@redhat.com>2014-01-14 04:37:54 +0400
committerMike Snitzer <snitzer@redhat.com>2014-01-15 08:23:04 +0400
commit2995fa78e423d7193f3b57835f6c1c75006a0315 (patch)
tree9f107c0503a3c0ba58559a62847e9236f3fd1951 /drivers/md/dm.h
parent55b082e614e219fb5199a6f93e648ed35d3c96d5 (diff)
downloadlinux-2995fa78e423d7193f3b57835f6c1c75006a0315.tar.xz
dm sysfs: fix a module unload race
This reverts commit be35f48610 ("dm: wait until embedded kobject is released before destroying a device") and provides an improved fix. The kobject release code that calls the completion must be placed in a non-module file, otherwise there is a module unload race (if the process calling dm_kobject_release is preempted and the DM module unloaded after the completion is triggered, but before dm_kobject_release returns). To fix this race, this patch moves the completion code to dm-builtin.c which is always compiled directly into the kernel if BLK_DEV_DM is selected. The patch introduces a new dm_kobject_holder structure, its purpose is to keep the completion and kobject in one place, so that it can be accessed from non-module code without the need to export the layout of struct mapped_device to that code. 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.h')
-rw-r--r--drivers/md/dm.h17
1 files changed, 16 insertions, 1 deletions
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 1ab2028559ca..c4569f02f50f 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -16,6 +16,7 @@
#include <linux/blkdev.h>
#include <linux/hdreg.h>
#include <linux/completion.h>
+#include <linux/kobject.h>
#include "dm-stats.h"
@@ -149,11 +150,25 @@ void dm_interface_exit(void);
/*
* sysfs interface
*/
+struct dm_kobject_holder {
+ struct kobject kobj;
+ struct completion completion;
+};
+
+static inline struct completion *dm_get_completion_from_kobject(struct kobject *kobj)
+{
+ return &container_of(kobj, struct dm_kobject_holder, kobj)->completion;
+}
+
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);
+
+/*
+ * The kobject helper
+ */
+void dm_kobject_release(struct kobject *kobj);
/*
* Targets for linear and striped mappings