On Fri, Jun 13, 2025 at 12:37:33PM +1000, NeilBrown wrote: > If two threads in the same namespace look up the same name at the same > time (which previously didn't exist), they will both enter > d_alloc_parallel() where neither will notice the other, so both will > create and install d_in_lookup() dentries, and then both will call > ->lookup, creating two identical inodes. > > I suspect that isn't fatal, but it does seem odd. > > Maybe proc_sys_compare should return 0 for d_in_lookup() (aka !inode) > dentries, and then proc_sys_revalidate() can perform the is_seen test > and return -EAGAIN if needed, and __lookup_slow() and others could > interpret that as meaning to "goto again" without calling > d_invalidate(). Umm... Not sure it's the best solution; let me think a bit. Just need to finish going through the ported rpc_pipefs series for the final look and posting it; should be about half an hour or so...
