Hi, I was playing around a bit, and noticed that trying to acquire an exclusive POSIX record lock on a bpf_link fd fails. I've traced this to the call to anon_inode_getfile from bpf_link_prime which effectively specifies O_RDONLY on the bpf_link struct file. This makes check_fmode_for_setlk return EBADF. This means the following: * flock(link, LOCK_EX): works * fcntl(link, SETLK, F_RDLCK): works * fcntl(link, SETLK, F_WRLCK): doesn't work Especially the discrepancy between flock(EX) and fcntl(WRLCK) has me puzzled. Should fcntl(WRLCK) work on a link? program fds are always O_RDWR as far as I can tell (so all locks work), while maps depend on map_flags. Best Lorenz -- Lorenz Bauer | Systems Engineer 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK www.cloudflare.com
