On Mon, 2023-02-13 at 10:22 -0600, Mike Christie wrote: > On 2/13/23 5:59 AM, Maurizio Lombardi wrote: > > st 8. 2. 2023 v 21:10 odesílatel David Jeffery <djeffery@xxxxxxxxxx > > > napsal: > > > > > > + /* > > > + * If the iscsi connection is over a loopback device from > > > using > > > + * iscsi and iscsit on the same system, we need to set > > > memalloc_noio to > > > + * prevent memory allocation deadlocks between target and > > > initiator. > > > + */ > > > + rcu_read_lock(); > > > + dst = rcu_dereference(conn->sock->sk->sk_dst_cache); > > > + if (dst && dst->dev && dst->dev->flags & IFF_LOOPBACK) > > > + loopback = true; > > > + rcu_read_unlock(); > > > > Hi Mike, > > I tested it, it works. The customer also confirmed that it fixes > > the > > deadlock on his setup. > > You never responded about why/how it's used in production. Is it some > sort > of clustering or container or what? > > The login related code can still swing back on you if it's run for a > relogin. > It would happen if we overqueue and a nop timesout because the iscsi > recv thread > is waiting for backend resources like a request/queue slot, or if > management tools > disable/enable the tpgt for reconfigs, etc. > Hi Mike, The use case described is as follows: "This customer moved their on-premise system to the cloud. Their on-premise system runs with two servers and one external storage and uses data mirroring software to mirror data. When moving to the cloud, customer wanted to implement a data mirror using data mirror software with two instances to reduce the cost of using the cloud infrastructure. To build a system with two instances, we use iSCSI to mirror data between a local disk on one instance and a local disk on the other instance. We coexist iSCSI initiator and target so that data mirroring software can access each disk through a unified interface." Thanks Laurence
