On Tue, Feb 27, 2018 at 03:08:01PM +0800, Jason Yan wrote: > 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 <yanaijie@xxxxxxxxxx> > CC: Ding Xiang <dingxiang@xxxxxxxxxx> > --- > 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; Can you please move the conditional to where we're consuming the flag instead? Thanks. -- tejun
