nvme: fix reconnection fail due to reserved tag allocation

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: nvme: fix reconnection fail due to reserved tag allocation We found a issue on production environment while using NVMe over RDMA, admin_q reconnect failed forever while remote target and network is ok. After dig into it, we found it may caused by a ABBA deadlock due to tag allocation. In my case, the tag was hold by a keep alive request waiting inside admin_q, as we quiesced admin_q while reset ctrl, so the request maked as idle and will not process before reset success. As fabric_q shares tagset with admin_q, while reconnect remote target, we need a tag for connect command, but the only one reserved tag was held by keep alive command which waiting inside admin_q. As a result, we failed to reconnect admin_q forever. In order to fix this issue, I think we should keep two reserved tags for admin queue.

References

• https://git.kernel.org/stable/c/149afee5c7418ec5db9d7387b9c9a5c1eb7ea2a8
• https://git.kernel.org/stable/c/ff2f90f88d78559802466ad1c84ac5bda4416b3a
• https://git.kernel.org/stable/c/6851778504cdb49431809b4ba061903d5f592c96
• https://git.kernel.org/stable/c/262da920896e2f2ab0e3947d9dbee0aa09045818
• https://git.kernel.org/stable/c/de105068fead55ed5c07ade75e9c8e7f86a00d1d