From: Hannes Reinecke hare@suse.de
[ Upstream commit 5faf50e9e9fdc2117c61ff7e20da49cd6a29e0ca ]
alua_bus_detach() might be running concurrently with alua_rtpg_work(), so we might trip over h->sdev == NULL and call BUG_ON(). The correct way of handling it is to not set h->sdev to NULL in alua_bus_detach(), and call rcu_synchronize() before the final delete to ensure that all concurrent threads have left the critical section. Then we can get rid of the BUG_ON() and replace it with a simple if condition.
Link: https://lore.kernel.org/r/1600167537-12509-1-git-send-email-jitendra.khasdev... Link: https://lore.kernel.org/r/20200924104559.26753-1-hare@suse.de Cc: Brian Bunker brian@purestorage.com Acked-by: Brian Bunker brian@purestorage.com Tested-by: Jitendra Khasdev jitendra.khasdev@oracle.com Reviewed-by: Jitendra Khasdev jitendra.khasdev@oracle.com Signed-off-by: Hannes Reinecke hare@suse.de Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/device_handler/scsi_dh_alua.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c index f32da0ca529e0..308bda2e9c000 100644 --- a/drivers/scsi/device_handler/scsi_dh_alua.c +++ b/drivers/scsi/device_handler/scsi_dh_alua.c @@ -658,8 +658,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg) rcu_read_lock(); list_for_each_entry_rcu(h, &tmp_pg->dh_list, node) { - /* h->sdev should always be valid */ - BUG_ON(!h->sdev); + if (!h->sdev) + continue; h->sdev->access_state = desc[0]; } rcu_read_unlock(); @@ -705,7 +705,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg) pg->expiry = 0; rcu_read_lock(); list_for_each_entry_rcu(h, &pg->dh_list, node) { - BUG_ON(!h->sdev); + if (!h->sdev) + continue; h->sdev->access_state = (pg->state & SCSI_ACCESS_STATE_MASK); if (pg->pref) @@ -1147,7 +1148,6 @@ static void alua_bus_detach(struct scsi_device *sdev) spin_lock(&h->pg_lock); pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock)); rcu_assign_pointer(h->pg, NULL); - h->sdev = NULL; spin_unlock(&h->pg_lock); if (pg) { spin_lock_irq(&pg->lock); @@ -1156,6 +1156,7 @@ static void alua_bus_detach(struct scsi_device *sdev) kref_put(&pg->kref, release_port_group); } sdev->handler_data = NULL; + synchronize_rcu(); kfree(h); }