4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sebastian Ott sebott@linux.ibm.com
[ Upstream commit f0f59a2fab8e52b9d582b39da39f22230ca80aee ]
Dasd uses completion_data from struct request to store per request private data - this is problematic since this member is part of a union which is also used by IO schedulers. Let the block layer maintain space for per request data behind each struct request.
Fixes crashes on block layer timeouts like this one:
Unable to handle kernel pointer dereference in virtual kernel address space Failing address: 0000000000000000 TEID: 0000000000000483 Fault in home space mode while using kernel ASCE. AS:0000000001308007 R3:00000000fffc8007 S:00000000fffcc000 P:000000000000013d Oops: 0004 ilc:2 [#1] PREEMPT SMP Modules linked in: [...] CPU: 0 PID: 1480 Comm: kworker/0:2H Not tainted 4.17.0-rc4-00046-gaa3bcd43b5af #203 Hardware name: IBM 3906 M02 702 (LPAR) Workqueue: kblockd blk_mq_timeout_work Krnl PSW : 0000000067ac406b 00000000b6960308 (do_raw_spin_trylock+0x30/0x78) R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000c00 0000000000000000 0000000000000000 0000000000000001 0000000000b9d3c8 0000000000000000 0000000000000001 00000000cf9639d8 0000000000000000 0700000000000000 0000000000000000 000000000099f09e 0000000000000000 000000000076e9d0 000000006247bb08 000000006247bae0 Krnl Code: 00000000001c159c: b90400c2 lgr %r12,%r2 00000000001c15a0: a7180000 lhi %r1,0 #00000000001c15a4: 583003a4 l %r3,932 >00000000001c15a8: ba132000 cs %r1,%r3,0(%r2) 00000000001c15ac: a7180001 lhi %r1,1 00000000001c15b0: a784000b brc 8,1c15c6 00000000001c15b4: c0e5004e72aa brasl %r14,b8fb08 00000000001c15ba: 1812 lr %r1,%r2 Call Trace: ([<0700000000000000>] 0x700000000000000) [<0000000000b9d3d2>] _raw_spin_lock_irqsave+0x7a/0xb8 [<000000000099f09e>] dasd_times_out+0x46/0x278 [<000000000076ea6e>] blk_mq_terminate_expired+0x9e/0x108 [<000000000077497a>] bt_for_each+0x102/0x130 [<0000000000774e54>] blk_mq_queue_tag_busy_iter+0x74/0xd8 [<000000000076fea0>] blk_mq_timeout_work+0x260/0x320 [<0000000000169dd4>] process_one_work+0x3bc/0x708 [<000000000016a382>] worker_thread+0x262/0x408 [<00000000001723a8>] kthread+0x160/0x178 [<0000000000b9e73a>] kernel_thread_starter+0x6/0xc [<0000000000b9e734>] kernel_thread_starter+0x0/0xc INFO: lockdep is turned off. Last Breaking-Event-Address: [<0000000000b9d3cc>] _raw_spin_lock_irqsave+0x74/0xb8
Kernel panic - not syncing: Fatal exception: panic_on_oops
Signed-off-by: Sebastian Ott sebott@linux.ibm.com Reviewed-by: Stefan Haberland sth@linux.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/s390/block/dasd.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/drivers/s390/block/dasd.c +++ b/drivers/s390/block/dasd.c @@ -3049,7 +3049,8 @@ static blk_status_t do_dasd_request(stru cqr->callback_data = req; cqr->status = DASD_CQR_FILLED; cqr->dq = dq; - req->completion_data = cqr; + *((struct dasd_ccw_req **) blk_mq_rq_to_pdu(req)) = cqr; + blk_mq_start_request(req); spin_lock(&block->queue_lock); list_add_tail(&cqr->blocklist, &block->ccw_queue); @@ -3073,12 +3074,13 @@ out: */ enum blk_eh_timer_return dasd_times_out(struct request *req, bool reserved) { - struct dasd_ccw_req *cqr = req->completion_data; struct dasd_block *block = req->q->queuedata; struct dasd_device *device; + struct dasd_ccw_req *cqr; unsigned long flags; int rc = 0;
+ cqr = *((struct dasd_ccw_req **) blk_mq_rq_to_pdu(req)); if (!cqr) return BLK_EH_NOT_HANDLED;
@@ -3184,6 +3186,7 @@ static int dasd_alloc_queue(struct dasd_ int rc;
block->tag_set.ops = &dasd_mq_ops; + block->tag_set.cmd_size = sizeof(struct dasd_ccw_req *); block->tag_set.nr_hw_queues = DASD_NR_HW_QUEUES; block->tag_set.queue_depth = DASD_MAX_LCU_DEV * DASD_REQ_PER_DEV; block->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;