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authorMikulas Patocka <mpatocka@redhat.com>2014-01-06 23:01:22 -0500
committerMike Snitzer <snitzer@redhat.com>2014-01-07 21:01:43 -0500
commitbe35f486108227e10fe5d96fd42fb2b344c59983 (patch)
tree9cfaef139722da4118b4fcd906eb1196d9577b23 /drivers/md/dm.h
parent1ddd641ddcfa46d719189468b6856e9b17381a61 (diff)
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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.h')
-rw-r--r--drivers/md/dm.h2
1 files changed, 2 insertions, 0 deletions
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 <linux/list.h>
#include <linux/blkdev.h>
#include <linux/hdreg.h>
+#include <linux/completion.h>
#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