The protocol for creating a new state in nfsd is to allocated the state leaving it largely uninitialised, add that state to the ->cl_stateids idr so as to reserve a state id, then complete initialisation of the state and only set ->sc_type to non-zero once the state is fully initialised. If a state is found in the idr with ->sc_type == 0, it is ignored. The ->cl_lock lock is used to avoid races - it is held while checking sc_type during lookup, and held when a non-zero value is stored in ->sc_type. ... except... hash_delegation_locked() finalises the initialisation of a delegation state, but does NOT hold ->cl_lock. So this patch takes ->cl_lock at the appropriate time w.r.t other locks, and so ensures there are no races (which are extremely unlikely in any case). As ->fi_lock is often taken when ->cl_lock is held, we need to take ->cl_lock first of those two. Currently ->cl_lock and state_lock are never both taken at the same time. We need both for this patch so an arbitrary choice is needed concerning which to take first. As state_lock is more global, it might be more contended, so take it first. Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> Signed-off-by: NeilBrown <neilb@xxxxxxx> --- fs/nfsd/nfs4state.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 40415929e2ae..042c7a50f425 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1317,6 +1317,7 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp) lockdep_assert_held(&state_lock); lockdep_assert_held(&fp->fi_lock); + lockdep_assert_held(&clp->cl_lock); if (nfs4_delegation_exists(clp, fp)) return -EAGAIN; @@ -5608,12 +5609,14 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, goto out_unlock; spin_lock(&state_lock); + spin_lock(&clp->cl_lock); spin_lock(&fp->fi_lock); if (fp->fi_had_conflict) status = -EAGAIN; else status = hash_delegation_locked(dp, fp); spin_unlock(&fp->fi_lock); + spin_unlock(&clp->cl_lock); spin_unlock(&state_lock); if (status) -- 2.42.1
