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 <[email protected]>
Signed-off-by: NeilBrown <[email protected]>
---
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