This is a note to let you know that I've just added the patch titled dm thin: fix a memory leak when passing discard bio down to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: dm-thin-fix-a-memory-leak-when-passing-discard-bio-down.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 948f581a53b704b984aa20df009f0a2b4cf7f907 Mon Sep 17 00:00:00 2001 From: Dennis Yang <dennisyang@xxxxxxxx> Date: Tue, 18 Apr 2017 15:27:06 +0800 Subject: dm thin: fix a memory leak when passing discard bio down From: Dennis Yang <dennisyang@xxxxxxxx> commit 948f581a53b704b984aa20df009f0a2b4cf7f907 upstream. dm-thin does not free the discard_parent bio after all chained sub bios finished. The following kmemleak report could be observed after pool with discard_passdown option processes discard bios in linux v4.11-rc7. To fix this, we drop the discard_parent bio reference when its endio (passdown_endio) called. unreferenced object 0xffff8803d6b29700 (size 256): comm "kworker/u8:0", pid 30349, jiffies 4379504020 (age 143002.776s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 01 00 00 00 00 00 00 f0 00 00 00 00 00 00 00 00 ................ backtrace: [<ffffffff81a5efd9>] kmemleak_alloc+0x49/0xa0 [<ffffffff8114ec34>] kmem_cache_alloc+0xb4/0x100 [<ffffffff8110eec0>] mempool_alloc_slab+0x10/0x20 [<ffffffff8110efa5>] mempool_alloc+0x55/0x150 [<ffffffff81374939>] bio_alloc_bioset+0xb9/0x260 [<ffffffffa018fd20>] process_prepared_discard_passdown_pt1+0x40/0x1c0 [dm_thin_pool] [<ffffffffa018b409>] break_up_discard_bio+0x1a9/0x200 [dm_thin_pool] [<ffffffffa018b484>] process_discard_cell_passdown+0x24/0x40 [dm_thin_pool] [<ffffffffa018b24d>] process_discard_bio+0xdd/0xf0 [dm_thin_pool] [<ffffffffa018ecf6>] do_worker+0xa76/0xd50 [dm_thin_pool] [<ffffffff81086239>] process_one_work+0x139/0x370 [<ffffffff810867b1>] worker_thread+0x61/0x450 [<ffffffff8108b316>] kthread+0xd6/0xf0 [<ffffffff81a6cd1f>] ret_from_fork+0x3f/0x70 [<ffffffffffffffff>] 0xffffffffffffffff Signed-off-by: Dennis Yang <dennisyang@xxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/dm-thin.c | 1 + 1 file changed, 1 insertion(+) --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1070,6 +1070,7 @@ static void passdown_endio(struct bio *b * to unmap (we ignore err). */ queue_passdown_pt2(bio->bi_private); + bio_put(bio); } static void process_prepared_discard_passdown_pt1(struct dm_thin_new_mapping *m) Patches currently in stable-queue which might be from dennisyang@xxxxxxxx are queue-4.9/dm-thin-fix-a-memory-leak-when-passing-discard-bio-down.patch