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Commit 10da4f79 authored by Jeff Mahoney's avatar Jeff Mahoney Committed by Linus Torvalds
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[PATCH] dm: add module ref counting 



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: default avatarJeff Mahoney <jeffm@suse.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7ec75f25

drivers/md/dm.c

+6 −0
Original line number Diff line number Diff line
@@ -852,6 +852,9 @@ static struct mapped_device *alloc_dev(unsigned int minor, int persistent) 
		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(unsigned int minor, int persistent) 
	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_device *md) 


	put_disk(md->disk);

	blk_cleanup_queue(md->queue);

	module_put(THIS_MODULE);

	kfree(md);

}