From: Jeff Mahoney Date: Thu, 14 Dec 2006 22:07:12 +0000 (+0100) Subject: dm: add module ref counting X-Git-Tag: v2.6.16.37-rc1~35 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2d22e81c67b9800c25801cccf75dd49ad5dd0bb3;p=people%2Fms%2Flinux.git 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. Signed-off-by: Jeff Mahoney Signed-off-by: Alasdair G Kergon Signed-off-by: Adrian Bunk --- diff --git a/drivers/md/dm.c b/drivers/md/dm.c index f6c8e8e4e8e2..973b6f6ff352 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -788,6 +788,9 @@ 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) @@ -848,6 +851,8 @@ static struct mapped_device *alloc_dev(unsigned int minor, int persistent) blk_put_queue(md->queue); free_minor(minor); bad1: + module_put(THIS_MODULE); + bad0: kfree(md); return NULL; } @@ -866,6 +871,7 @@ static void free_dev(struct mapped_device *md) free_minor(minor); put_disk(md->disk); blk_put_queue(md->queue); + module_put(THIS_MODULE); kfree(md); }