xfs_file_splice_read: possible circular locking dependency detected

[CAI Qian]

----- Original Message -----
> Fundamentally a splice infrastructure problem. If we let splice race
> with hole punch and other fallocate() based extent manipulations to
> avoid this lockdep warning, we allow potential for read or write to
> regions of the file that have been freed. We can live with having
> lockdep complain about this potential deadlock as it is unlikely to
> ever occur in practice. The other option is simply not an acceptible
> solution....
The problem with living with having this lockdep complain that
it seems once this lockdep happens, it will prevent other complains from
showing up. For example, I have to apply the commit dc3a04d to fix an early
rcu lockdep first during the bisecting.
   CAI Qian