From: Jeff Mahoney 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 Signed-off-by: Alasdair G Kergon Cc: Signed-off-by: Andrew Morton --- drivers/md/dm.c | 6 ++++++ 1 files changed, 6 insertions(+) diff -puN drivers/md/dm.c~dm-add-module-ref-counting drivers/md/dm.c --- devel/drivers/md/dm.c~dm-add-module-ref-counting 2006-05-25 15:15:32.000000000 -0700 +++ devel-akpm/drivers/md/dm.c 2006-05-25 15:15:32.000000000 -0700 @@ -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); } _