[for-6.16-final PATCH 7/9] Revert "nfs_localio: use cmpxchg() to install new nfs_file_localio"

Mike Snitzer
2025-07-14T03:14:11Z

This reverts commit 9fccbbec13a73ae0e75448a00e20dadc8c511c8c.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
fs/nfs/localio.c | 11 ++++++++---
fs/nfs_common/nfslocalio.c | 39 +++++++++++++++++++++-----------------
2 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
index 7a33da477da3..a4bacd9a5052 100644
--- a/fs/nfs/localio.c
+++ b/fs/nfs/localio.c
@@ -282,9 +282,14 @@ nfs_local_open_fh(struct nfs_client *clp, const struct cred *cred,
return NULL;
rcu_read_lock();
/* try to swap in the pointer */
- nf = unrcu_pointer(cmpxchg(pnf, NULL, RCU_INITIALIZER(new)));
- if (!nf)
- swap(nf, new);
+ spin_lock(&clp->cl_uuid.lock);
+ nf = rcu_dereference_protected(*pnf, 1);
+ if (!nf) {
+ nf = new;
+ new = NULL;
+ rcu_assign_pointer(*pnf, nf);
+ }
+ spin_unlock(&clp->cl_uuid.lock);
}
nf = nfs_local_file_get(nf);
rcu_read_unlock();
diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c
index bdf251332b6b..6a0bdea6d644 100644
--- a/fs/nfs_common/nfslocalio.c
+++ b/fs/nfs_common/nfslocalio.c
@@ -273,8 +273,8 @@ EXPORT_SYMBOL_GPL(nfs_open_local_fh);

void nfs_close_local_fh(struct nfs_file_localio *nfl)
{
- struct nfsd_file *ro_nf;
- struct nfsd_file *rw_nf;
+ struct nfsd_file *ro_nf = NULL;
+ struct nfsd_file *rw_nf = NULL;
nfs_uuid_t *nfs_uuid;

rcu_read_lock();
@@ -285,23 +285,28 @@ void nfs_close_local_fh(struct nfs_file_localio *nfl)
return;
}

- ro_nf = unrcu_pointer(xchg(&nfl->ro_file, NULL));
- rw_nf = unrcu_pointer(xchg(&nfl->rw_file, NULL));
+ ro_nf = rcu_access_pointer(nfl->ro_file);
+ rw_nf = rcu_access_pointer(nfl->rw_file);
+ if (ro_nf || rw_nf) {
+ spin_lock(&nfs_uuid->lock);
+ if (ro_nf)
+ ro_nf = rcu_dereference_protected(xchg(&nfl->ro_file, NULL), 1);
+ if (rw_nf)
+ rw_nf = rcu_dereference_protected(xchg(&nfl->rw_file, NULL), 1);

- spin_lock(&nfs_uuid->lock);
- /* Remove nfl from nfs_uuid->files list */
- list_del_init(&nfl->list);
- spin_unlock(&nfs_uuid->lock);
+ /* Remove nfl from nfs_uuid->files list */
+ RCU_INIT_POINTER(nfl->nfs_uuid, NULL);
+ list_del_init(&nfl->list);
+ spin_unlock(&nfs_uuid->lock);
+ rcu_read_unlock();
+
+ if (ro_nf)
+ nfs_to_nfsd_file_put_local(ro_nf);
+ if (rw_nf)
+ nfs_to_nfsd_file_put_local(rw_nf);
+ return;
+ }
rcu_read_unlock();
- /* Now we can allow racing nfs_close_local_fh() to
- * skip the locking.
- */
- RCU_INIT_POINTER(nfl->nfs_uuid, NULL);
-
- if (ro_nf)
- nfs_to_nfsd_file_put_local(ro_nf);
- if (rw_nf)
- nfs_to_nfsd_file_put_local(rw_nf);
}
EXPORT_SYMBOL_GPL(nfs_close_local_fh);

--
2.44.0