We've got a kernel panic when using sata disk with sas controller: [115946.152283] Unable to handle kernel NULL pointer dereference at virtual address 000007d8 [115946.223963] CPU: 0 PID: 22175 Comm: kworker/0:1 Tainted: G W OEL 4.14.0 #1 [115946.232925] Workqueue: events ata_scsi_hotplug [115946.237938] task: ffff8021ee50b180 task.stack: ffff00000d5d0000 [115946.244717] PC is at sas_find_dev_by_rphy+0x44/0x114 [115946.250224] LR is at sas_find_dev_by_rphy+0x3c/0x114 ...... [115946.355701] Process kworker/0:1 (pid: 22175, stack limit = 0xffff00000d5d0000) [115946.363369] Call trace: [115946.456356] [<ffff000008878a9c>] sas_find_dev_by_rphy+0x44/0x114 [115946.462908] [<ffff000008878b8c>] sas_target_alloc+0x20/0x5c [115946.469408] [<ffff00000885a31c>] scsi_alloc_target+0x250/0x308 [115946.475781] [<ffff00000885ba30>] __scsi_add_device+0xb0/0x154 [115946.481991] [<ffff0000088b520c>] ata_scsi_scan_host+0x180/0x218 [115946.488367] [<ffff0000088b53d8>] ata_scsi_hotplug+0xb0/0xcc [115946.494801] [<ffff0000080ebd70>] process_one_work+0x144/0x390 [115946.501115] [<ffff0000080ec100>] worker_thread+0x144/0x418 [115946.507093] [<ffff0000080f2c98>] kthread+0x10c/0x138 [115946.512792] [<ffff0000080855dc>] ret_from_fork+0x10/0x18
We found that Ding Xiang has reported a similar bug before: https://patchwork.kernel.org/patch/9179817/ And this bug still exists in mainline. Since libsas handles hotplug and device adding/removing itself, do not need to schedule ata hot plug task here if it is a sas host. Signed-off-by: Jason Yan <yanai...@huawei.com> CC: Ding Xiang <dingxi...@huawei.com> --- drivers/ata/libata-eh.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c index 11c3137d7b0a..97aeac45b22c 100644 --- a/drivers/ata/libata-eh.c +++ b/drivers/ata/libata-eh.c @@ -1384,7 +1384,9 @@ void ata_eh_detach_dev(struct ata_device *dev) if (ata_scsi_offline_dev(dev)) { dev->flags |= ATA_DFLAG_DETACHED; - ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG; + /* libsas handles the hotplug itself */ + if (!(ap->flags & ATA_FLAG_SAS_HOST)) + ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG; } /* clear per-dev EH info */ @@ -3256,7 +3258,9 @@ static int ata_eh_revalidate_and_attach(struct ata_link *link, } spin_lock_irqsave(ap->lock, flags); - ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG; + /* libsas handles the hotplug itself */ + if (!(ap->flags & ATA_FLAG_SAS_HOST)) + ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG; spin_unlock_irqrestore(ap->lock, flags); /* new device discovered, configure xfermode */ -- 2.13.6
