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Subject[patch 14/37] dm: add module ref counting
-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jeff Mahoney <jeffm@suse.com>

The reference counting on dm-mod is zero if no mapped devices are open. This
is incorrect, and can lead to an oops if the module is unloaded while mapped
devices exist.

This patch claims a reference to the module whenever a device is created, and
drops it again when the device is freed.

Devices must be removed before dm-mod is unloaded.

[akpm: too late for 2.6.17 - suitable for 2.6.17.x after it has settled]

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

drivers/md/dm.c | 6 ++++++
1 file changed, 6 insertions(+)

--- linux-2.6.17.11.orig/drivers/md/dm.c
+++ linux-2.6.17.11/drivers/md/dm.c
@@ -852,6 +852,9 @@ static struct mapped_device *alloc_dev(u
return NULL;
}

+ if (!try_module_get(THIS_MODULE))
+ goto bad0;
+
/* get a minor number for the dev */
r = persistent ? specific_minor(md, minor) : next_free_minor(md, &minor);
if (r < 0)
@@ -918,6 +921,8 @@ static struct mapped_device *alloc_dev(u
blk_cleanup_queue(md->queue);
free_minor(minor);
bad1:
+ module_put(THIS_MODULE);
+ bad0:
kfree(md);
return NULL;
}
@@ -941,6 +946,7 @@ static void free_dev(struct mapped_devic

put_disk(md->disk);
blk_cleanup_queue(md->queue);
+ module_put(THIS_MODULE);
kfree(md);
}

--
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