Shyam Prasad N <nspmangalore@xxxxxxxxx> writes: > There is a race condition that exists between cifsd and I/O threads > when the tcp connection is broken. The cifsd thread marks the > server/session/tcon structures for reconnect, and recreates the > socket, and sets 1 credit for this server. This only changes after the > next negotiate/session-setup completes, where it can get more credits. > During this window, if any ongoing I/O requires more than 1 credit, > then it will return with smb3_insufficient_credits (note that slightly > earlier in the same code, we identify reconnect with > smb3_reconnect_detected, but do nothing about it). The I/O will now > leak -EHOSTDOWN or -EAGAIN into userspace. I don't see why it would be a problem returning either -EAGAIN or -EHOSTDOWN back to userspace on *soft* mounts. Isn't this what we want? If the syscall gets signaled while we are waiting for the tcp connection being restablished, then we return -ERESTARTSYS. See wait_event_interruptible_timeout() in smb2_reconnect(). > I feel that we should return a special error (-ERESTARTSYS?) when > smb3_reconnect_detected, and use this errno to ask the caller to > restart the syscall. Userspace doesn't handle -ERESTARTSYS. When we return -ERESTARTSYS from a signaled syscall, this means that the kernel will either handle the signal and restart syscall from the beginning, or return -EINTR back to userspace.
