On 2023/9/7 9:45, Ding Hui wrote:
On 2023/9/6 23:51, Mike Christie wrote:
On 8/3/23 6:28 AM, Huang Cun wrote:
When a disk fails to attach, the struct rdac_dh_data is released,
but it is not removed from the ctlr->dh_list. When attaching another
disk, the released rdac_dh_data will be accessed and the following
BUG_ON() may be observed:
[ 414.696167] scsi 5:0:0:7: rdac: Attach failed (8)
...
[ 423.615364] kernel BUG at drivers/scsi/device_handler/scsi_dh_rdac.c:427!
[ 423.615731] invalid opcode: 0000 [#1] SMP NOPTI
...
[ 423.623247] Call Trace:
[ 423.623598] rdac_bus_attach+0x203/0x4c0
[ 423.623949] ? scsi_dh_handler_attach+0x2d/0x90
[ 423.624300] scsi_dh_handler_attach+0x2d/0x90
[ 423.624652] scsi_sysfs_add_sdev+0x88/0x270
[ 423.625004] scsi_probe_and_add_lun+0xc47/0xd50
[ 423.625354] scsi_report_lun_scan+0x339/0x3b0
[ 423.625705] __scsi_scan_target+0xe9/0x220
[ 423.626056] scsi_scan_target+0xf6/0x100
[ 423.626404] fc_scsi_scan_rport+0xa5/0xb0
[ 423.626757] process_one_work+0x15e/0x3f0
[ 423.627106] worker_thread+0x4c/0x440
[ 423.627453] ? rescuer_thread+0x350/0x350
[ 423.627804] kthread+0xf8/0x130
[ 423.628153] ? kthread_destroy_worker+0x40/0x40
[ 423.628509] ret_from_fork+0x1f/0x40
Fixes: 1a5dc166cd88 ("scsi_dh_rdac: update 'access_state' field")
Signed-off-by: Huang Cun <huangcun@xxxxxxxxxxxxxx>
Signed-off-by: Ding Hui <dinghui@xxxxxxxxxxxxxx>
Cc: Donglin Peng <pengdonglin@xxxxxxxxxxxxxx>
---
drivers/scsi/device_handler/scsi_dh_rdac.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
index c5538645057a..9d487c2b7708 100644
--- a/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -762,8 +762,10 @@ static int rdac_bus_attach(struct scsi_device *sdev)
clean_ctlr:
spin_lock(&list_lock);
+ list_del_rcu(&h->node);
kref_put(&h->ctlr->kref, release_controller);
spin_unlock(&list_lock);
+ synchronize_rcu();
Should this be:
spin_lock(&list_lock);
list_del_rcu(&h->node);
spin_unlock(&list_lock);
synchronize_rcu();
kref_put(&h->ctlr->kref, release_controller);
?
If you do the synchronize_rcu after the kref_put, then the kref_put
could free the rdac_dh_data, while check_ownership is still
accessing the rdac_dh_data, right?
You are right.
But I think we should keep the kref_put() and release callback be protected by list_lock, and only free
the ctlr after synchronize_rcu().
Sorry, I thought again, maybe we don't need to worry about it.
The ctlr->kref is protected by list_lock, and release_controller() DO free the ctlr, NOT rdac_dh_data,
kfree(rdac_dh_data) is already after synchronize_rcu().
If check_ownership() shared the same ctlr, the kref must be greater than or equal to 2, so the ctlr will
not be released by kref_put(). On the other hand, if the ctlr is different, releasing it will not affect
others.
--
Thanks,
- Ding Hui
