[OpenPower-Firmware] [PATCH] scsi: ipr: Fix softlockup when rescanning devices in petitboot

[Joel Stanley]

On Fri, 13 Mar 2020 at 05:43, Vasant Hegde
<hegdevasant at linux.vnet.ibm.com> wrote:

Thanks, this has been merged into the v5.4.25-openpower1 kernel release.

>
> From: Wen Xiong <wenxiong at linux.vnet.ibm.com>
>
> When trying to rescan disks in petitboot shell, we hit the following
> softlockup stacktrace:
>
> Kernel panic - not syncing: System is deadlocked on memory
> [  241.223394] CPU: 32 PID: 693 Comm: sh Not tainted 5.4.16-openpower1 #1
> [  241.223406] Call Trace:
> [  241.223415] [c0000003f07c3180] [c000000000493fc4] dump_stack+0xa4/0xd8 (unreliable)
> [  241.223432] [c0000003f07c31c0] [c00000000007d4ac] panic+0x148/0x3cc
> [  241.223446] [c0000003f07c3260] [c000000000114b10] out_of_memory+0x468/0x4c4
> [  241.223461] [c0000003f07c3300] [c0000000001472b0] __alloc_pages_slowpath+0x594/0x6d8
> [  241.223476] [c0000003f07c3420] [c00000000014757c] __alloc_pages_nodemask+0x188/0x1a4
> [  241.223492] [c0000003f07c34a0] [c000000000153e10] alloc_pages_current+0xcc/0xd8
> [  241.223508] [c0000003f07c34e0] [c0000000001577ac] alloc_slab_page+0x30/0x98
> [  241.223524] [c0000003f07c3520] [c0000000001597fc] new_slab+0x138/0x40c
> [  241.223538] [c0000003f07c35f0] [c00000000015b204] ___slab_alloc+0x1e4/0x404
> [  241.223552] [c0000003f07c36c0] [c00000000015b450] __slab_alloc+0x2c/0x48
> [  241.223566] [c0000003f07c36f0] [c00000000015b754] kmem_cache_alloc_node+0x9c/0x1b4
> [  241.223582] [c0000003f07c3760] [c000000000218c48] blk_alloc_queue_node+0x34/0x270
> [  241.223599] [c0000003f07c37b0] [c000000000226574] blk_mq_init_queue+0x2c/0x78
> [  241.223615] [c0000003f07c37e0] [c0000000002ff710] scsi_mq_alloc_queue+0x28/0x70
> [  241.223631] [c0000003f07c3810] [c0000000003005b8] scsi_alloc_sdev+0x184/0x264
> [  241.223647] [c0000003f07c38a0] [c000000000300ba0] scsi_probe_and_add_lun+0x288/0xa3c
> [  241.223663] [c0000003f07c3a00] [c000000000301768] __scsi_scan_target+0xcc/0x478
> [  241.223679] [c0000003f07c3b20] [c000000000301c64] scsi_scan_channel.part.9+0x74/0x7c
> [  241.223696] [c0000003f07c3b70] [c000000000301df4] scsi_scan_host_selected+0xe0/0x158
> [  241.223712] [c0000003f07c3bd0] [c000000000303f04] store_scan+0x104/0x114
> [  241.223727] [c0000003f07c3cb0] [c0000000002d5ac4] dev_attr_store+0x30/0x4c
> [  241.223741] [c0000003f07c3cd0] [c0000000001dbc34] sysfs_kf_write+0x64/0x78
> [  241.223756] [c0000003f07c3cf0] [c0000000001da858] kernfs_fop_write+0x170/0x1b8
> [  241.223773] [c0000003f07c3d40] [c0000000001621fc] __vfs_write+0x34/0x60
> [  241.223787] [c0000003f07c3d60] [c000000000163c2c] vfs_write+0xa8/0xcc
> [  241.223802] [c0000003f07c3db0] [c000000000163df4] ksys_write+0x70/0xbc
> [  241.223816] [c0000003f07c3e20] [c00000000000b40c] system_call+0x5c/0x68
>
> As a part of the scan process Linux will allocate and configure a
> scsi_device for each target to be scanned. If the device is not present,
> then the scsi_device is torn down. As a part of scsi_device teardown a
> workqueue item will be scheduled and the lockups we see are because there
> are 250k workqueue items to be processed.  Accoding to the specification of
> SIS-64 sas controller, max_channel should be decreased on SIS-64 adapters
> to 4.
>
> The patch fixes softlockup issue.
>
> Thanks for Oliver Halloran's help with debugging and explanation!
>
> Link: https://lore.kernel.org/r/1583510248-23672-1-git-send-email-wenxiong@linux.vnet.ibm.com
> Signed-off-by: Wen Xiong <wenxiong at linux.vnet.ibm.com>
> Signed-off-by: Martin K. Petersen <martin.petersen at oracle.com>
> [Backported to op-build - Vasant]
> Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
> ---
>  drivers/scsi/ipr.c | 3 ++-
>  drivers/scsi/ipr.h | 1 +
>  2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
> index 079c04bc448a..7a57b61f0340 100644
> --- a/drivers/scsi/ipr.c
> +++ b/drivers/scsi/ipr.c
> @@ -9947,6 +9947,7 @@ static void ipr_init_ioa_cfg(struct ipr_ioa_cfg *ioa_cfg,
>         ioa_cfg->max_devs_supported = ipr_max_devs;
>
>         if (ioa_cfg->sis64) {
> +               host->max_channel = IPR_MAX_SIS64_BUSES;
>                 host->max_id = IPR_MAX_SIS64_TARGETS_PER_BUS;
>                 host->max_lun = IPR_MAX_SIS64_LUNS_PER_TARGET;
>                 if (ipr_max_devs > IPR_MAX_SIS64_DEVS)
> @@ -9955,6 +9956,7 @@ static void ipr_init_ioa_cfg(struct ipr_ioa_cfg *ioa_cfg,
>                                            + ((sizeof(struct ipr_config_table_entry64)
>                                                * ioa_cfg->max_devs_supported)));
>         } else {
> +               host->max_channel = IPR_VSET_BUS;
>                 host->max_id = IPR_MAX_NUM_TARGETS_PER_BUS;
>                 host->max_lun = IPR_MAX_NUM_LUNS_PER_TARGET;
>                 if (ipr_max_devs > IPR_MAX_PHYSICAL_DEVS)
> @@ -9964,7 +9966,6 @@ static void ipr_init_ioa_cfg(struct ipr_ioa_cfg *ioa_cfg,
>                                                * ioa_cfg->max_devs_supported)));
>         }
>
> -       host->max_channel = IPR_VSET_BUS;
>         host->unique_id = host->host_no;
>         host->max_cmd_len = IPR_MAX_CDB_LEN;
>         host->can_queue = ioa_cfg->max_cmds;
> diff --git a/drivers/scsi/ipr.h b/drivers/scsi/ipr.h
> index a67baeb36d1f..b97aa9ac2ffe 100644
> --- a/drivers/scsi/ipr.h
> +++ b/drivers/scsi/ipr.h
> @@ -1300,6 +1300,7 @@ struct ipr_resource_entry {
>  #define IPR_ARRAY_VIRTUAL_BUS                  0x1
>  #define IPR_VSET_VIRTUAL_BUS                   0x2
>  #define IPR_IOAFP_VIRTUAL_BUS                  0x3
> +#define IPR_MAX_SIS64_BUSES                    0x4
>
>  #define IPR_GET_RES_PHYS_LOC(res) \
>         (((res)->bus << 24) | ((res)->target << 8) | (res)->lun)
> --
> 2.21.1
>