Re: [PATCH] blk-mq: re-build queue map in case of kdump kernel

[Jens Axboe <axboe@kernel.dk>]

On 12/6/18 7:55 PM, Ming Lei wrote:
> Now almost all .map_queues() implementation based on managed irq
> affinity doesn't update queue mapping and it just retrieves the
> old built mapping, so if nr_hw_queues is changed, the mapping talbe
> includes stale mapping. And only blk_mq_map_queues() may rebuild
> the mapping talbe.
> 
> One case is that we limit .nr_hw_queues as 1 in case of kdump kernel.
> However, drivers often builds queue mapping before allocating tagset
> via pci_alloc_irq_vectors_affinity(), but set->nr_hw_queues can be set
> as 1 in case of kdump kernel, so wrong queue mapping is used, and
> kernel panic[1] is observed during booting.
> 
> This patch fixes the kernel panic triggerd on nvme by rebulding the
> mapping table via blk_mq_map_queues().
> 
> [1] kernel panic log
> [    4.438371] nvme nvme0: 16/0/0 default/read/poll queues
> [    4.443277] BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
> [    4.444681] PGD 0 P4D 0
> [    4.445367] Oops: 0000 [#1] SMP NOPTI
> [    4.446342] CPU: 3 PID: 201 Comm: kworker/u33:10 Not tainted 4.20.0-rc5-00664-g5eb02f7ee1eb-dirty #459
> [    4.447630] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014
> [    4.448689] Workqueue: nvme-wq nvme_scan_work [nvme_core]
> [    4.449368] RIP: 0010:blk_mq_map_swqueue+0xfb/0x222
> [    4.450596] Code: 04 f5 20 28 ef 81 48 89 c6 39 55 30 76 93 89 d0 48 c1 e0 04 48 03 83 f8 05 00 00 48 8b 00 42 8b 3c 28 48 8b 43 58 48 8b 04 f8 <48> 8b b8 98 00 00 00 4c 0f a3 37 72 42 f0 4c 0f ab 37 66 8b b8 f6
> [    4.453132] RSP: 0018:ffffc900023b3cd8 EFLAGS: 00010286
> [    4.454061] RAX: 0000000000000000 RBX: ffff888174448000 RCX: 0000000000000001
> [    4.456480] RDX: 0000000000000001 RSI: ffffe8feffc506c0 RDI: 0000000000000001
> [    4.458750] RBP: ffff88810722d008 R08: ffff88817647a880 R09: 0000000000000002
> [    4.464580] R10: ffffc900023b3c10 R11: 0000000000000004 R12: ffff888174448538
> [    4.467803] R13: 0000000000000004 R14: 0000000000000001 R15: 0000000000000001
> [    4.469220] FS:  0000000000000000(0000) GS:ffff88817bac0000(0000) knlGS:0000000000000000
> [    4.471554] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    4.472464] CR2: 0000000000000098 CR3: 0000000174e4e001 CR4: 0000000000760ee0
> [    4.474264] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [    4.476007] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [    4.477061] PKRU: 55555554
> [    4.477464] Call Trace:
> [    4.478731]  blk_mq_init_allocated_queue+0x36a/0x3ad
> [    4.479595]  blk_mq_init_queue+0x32/0x4e
> [    4.480178]  nvme_validate_ns+0x98/0x623 [nvme_core]
> [    4.480963]  ? nvme_submit_sync_cmd+0x1b/0x20 [nvme_core]
> [    4.481685]  ? nvme_identify_ctrl.isra.8+0x70/0xa0 [nvme_core]
> [    4.482601]  nvme_scan_work+0x23a/0x29b [nvme_core]
> [    4.483269]  ? _raw_spin_unlock_irqrestore+0x25/0x38
> [    4.483930]  ? try_to_wake_up+0x38d/0x3b3
> [    4.484478]  ? process_one_work+0x179/0x2fc
> [    4.485118]  process_one_work+0x1d3/0x2fc
> [    4.485655]  ? rescuer_thread+0x2ae/0x2ae
> [    4.486196]  worker_thread+0x1e9/0x2be
> [    4.486841]  kthread+0x115/0x11d
> [    4.487294]  ? kthread_park+0x76/0x76
> [    4.487784]  ret_from_fork+0x3a/0x50
> [    4.488322] Modules linked in: nvme nvme_core qemu_fw_cfg virtio_scsi ip_tables
> [    4.489428] Dumping ftrace buffer:
> [    4.489939]    (ftrace buffer empty)
> [    4.490492] CR2: 0000000000000098
> [    4.491052] ---[ end trace 03cd268ad5a86ff7 ]---
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: linux-nvme@lists.infradead.org
> Cc: David Milburn <dmilburn@redhat.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  block/blk-mq.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 900550594651..a3e463a726a6 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -38,6 +38,11 @@
>  #include "blk-mq-sched.h"
>  #include "blk-rq-qos.h"
>  
> +static inline bool blk_mq_kdump_kernel(void)
> +{
> +	return !!is_kdump_kernel();
> +}

Let's drop the redundant !! here, and the wrapper? I would imagine the
wrapper is handy for testing outside of kdump, but I don't think we
should include it in the final.

Otherwise this looks fine, I can test it here too.

-- 
Jens Axboe