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Subject[PATCH AUTOSEL 4.9 11/15] scsi: ipr: Fix softlockup when rescanning devices in petitboot
Date
From: Wen Xiong <wenxiong@linux.vnet.ibm.com>

[ Upstream commit 394b61711f3ce33f75bf70a3e22938464a13b3ee ]

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@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 c5bc41d97f84b..7760b9a1e0aea 100644
--- a/drivers/scsi/ipr.c
+++ b/drivers/scsi/ipr.c
@@ -9818,6 +9818,7 @@ 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)
@@ -9826,6 +9827,7 @@ 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)
@@ -9835,7 +9837,6 @@ 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 8995053d01b3f..5b2388266c4c3 100644
--- a/drivers/scsi/ipr.h
+++ b/drivers/scsi/ipr.h
@@ -1306,6 +1306,7 @@ 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)
--
2.20.1
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