From: Jun'ichi Nomura This patch fixes a regression introduced in v3.8, which causes oops like this when dm-multipath is used: general protection fault: 0000 [#1] SMP RIP: 0010:[] [] mempool_free+0x24/0xb0 Call Trace: [] bio_put+0x97/0xc0 [] end_clone_bio+0x35/0x90 [dm_mod] [] bio_endio+0x1d/0x30 [] req_bio_endio.isra.51+0xa3/0xe0 [] blk_update_request+0x118/0x520 [] blk_update_bidi_request+0x27/0xa0 [] blk_end_bidi_request+0x2c/0x80 [] blk_end_request+0x10/0x20 [] scsi_io_completion+0xfb/0x6c0 [scsi_mod] [] scsi_finish_command+0xbd/0x120 [scsi_mod] [] scsi_softirq_done+0x13f/0x160 [scsi_mod] [] blk_done_softirq+0x80/0xa0 [] __do_softirq+0xf1/0x250 [] call_softirq+0x1c/0x30 [] do_softirq+0x8d/0xc0 [] irq_exit+0xd5/0xe0 [] do_IRQ+0x63/0xe0 [] common_interrupt+0x6f/0x6f [] srp_queuecommand+0x8c/0xcb0 [ib_srp] [] scsi_dispatch_cmd+0x148/0x310 [scsi_mod] [] scsi_request_fn+0x31e/0x520 [scsi_mod] [] __blk_run_queue+0x37/0x50 [] blk_delay_work+0x29/0x40 [] process_one_work+0x1c3/0x5c0 [] worker_thread+0x15e/0x440 [] kthread+0xdb/0xe0 [] ret_from_fork+0x7c/0xb0 The regression was introduced by the change c0820cf5 "dm: introduce per_bio_data", where dm started to replace bioset during table replacement. For bio-based dm, it is good because clone bios do not exist during the table replacement. For request-based dm, however, (not-yet-mapped) clone bios may stay in request queue and survive during the table replacement. So freeing the old bioset could cause the oops in bio_put(). Since the size of front_pad may change only with bio-based dm, it is not necessary to replace bioset for request-based dm. Reported-by: Bart Van Assche Tested-by: Bart Van Assche Signed-off-by: Jun'ichi Nomura Acked-by: Mikulas Patocka Acked-by: Mike Snitzer Cc: Signed-off-by: Alasdair G Kergon --- drivers/md/dm.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-) Index: linux/drivers/md/dm.c =================================================================== --- linux.orig/drivers/md/dm.c +++ linux/drivers/md/dm.c @@ -1947,15 +1947,27 @@ static void __bind_mempools(struct mappe { struct dm_md_mempools *p = dm_table_get_md_mempools(t); - if (md->io_pool && (md->tio_pool || dm_table_get_type(t) == DM_TYPE_BIO_BASED) && md->bs) { - /* - * The md already has necessary mempools. Reload just the - * bioset because front_pad may have changed because - * a different table was loaded. - */ - bioset_free(md->bs); - md->bs = p->bs; - p->bs = NULL; + if (md->io_pool && md->bs) { + /* The md already has necessary mempools. */ + if (dm_table_get_type(t) == DM_TYPE_BIO_BASED) { + /* + * Reload bioset because front_pad may have changed + * because a different table was loaded. + */ + bioset_free(md->bs); + md->bs = p->bs; + p->bs = NULL; + } else if (dm_table_get_type(t) == DM_TYPE_REQUEST_BASED) { + BUG_ON(!md->tio_pool); + /* + * There's no need to reload with request-based dm + * because the size of front_pad doesn't change. + * Note for future: If you are to reload bioset, + * prep-ed requests in the queue may refer + * to bio from the old bioset, so you must walk + * through the queue to unprep. + */ + } goto out; }