From: Mike Snitzer The following BUG is hit on the first read that is submitted to a dm flakey test device while the device is "down" if the corrupt_bio_byte feature wasn't requested when the device's table was loaded. Example DM table that will hit this BUG: 0 2097152 flakey 8:0 2048 0 30 This bug was introduced by commit a3998799fb4df0b0af8271a7d50c4269032397aa (dm flakey: add corrupt_bio_byte feature) in v3.1-rc1. BUG: unable to handle kernel paging request at ffff8801cfce3fff IP: [] corrupt_bio_data+0x6e/0xae [dm_flakey] PGD 1606063 PUD 0 Oops: 0002 [#1] SMP ... Call Trace: [] flakey_end_io+0x42/0x48 [dm_flakey] [] clone_endio+0x54/0xb6 [dm_mod] [] bio_endio+0x2d/0x2f [] req_bio_endio+0x96/0x9f [] blk_update_request+0x1dc/0x3a9 [] ? rcu_read_unlock+0x21/0x23 [] blk_update_bidi_request+0x20/0x6e [] blk_end_bidi_request+0x1f/0x5d [] blk_end_request+0x10/0x12 [] scsi_io_completion+0x1e5/0x4b1 [] scsi_finish_command+0xec/0xf5 [] scsi_softirq_done+0xff/0x108 [] blk_done_softirq+0x84/0x98 [] __do_softirq+0xe3/0x1d5 [] ? _raw_spin_lock+0x62/0x69 [] ? handle_irq_event+0x4c/0x61 [] call_softirq+0x1c/0x30 [] do_softirq+0x4b/0xa3 [] irq_exit+0x53/0xca [] do_IRQ+0x9d/0xb4 [] common_interrupt+0x73/0x73 ... Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org # 3.1+ Signed-off-by: Alasdair G Kergon --- drivers/md/dm-flakey.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-3.3-rc6/drivers/md/dm-flakey.c =================================================================== --- linux-3.3-rc6.orig/drivers/md/dm-flakey.c +++ linux-3.3-rc6/drivers/md/dm-flakey.c @@ -323,7 +323,7 @@ static int flakey_end_io(struct dm_targe * Corrupt successful READs while in down state. * If flags were specified, only corrupt those that match. */ - if (!error && bio_submitted_while_down && + if (fc->corrupt_bio_byte && !error && bio_submitted_while_down && (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) && all_corrupt_bio_flags_match(bio, fc)) corrupt_bio_data(bio, fc);