[PATCH 4/6] nfs_localio: duplicate nfs_close_local_fh()

NeilBrown
2025-05-09T00:49:15Z

nfs_close_local_fh() is called from two different places for quite
different use case.

It is called from nfs_uuid_put() when the nfs_uuid is being detached -
possibly because the nfs server is not longer serving that filesystem.
In this case there will always be an nfs_uuid and so rcu_read_lock() is
not needed.

It is also called when the nfs_file_localio is no longer needed. In
this case there may not be an active nfs_uuid.

These two can race, and handling the race properly while avoiding
excessive locking will require different handling on each side.

This patch prepares the way by opencoding nfs_close_local_fh() into
nfs_uuid_put(), then simplifying the code there as befits the context.

Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client")
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/nfs_common/nfslocalio.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c
index 503f85f64b76..49c59f0c78c6 100644
--- a/fs/nfs_common/nfslocalio.c
+++ b/fs/nfs_common/nfslocalio.c
@@ -171,7 +171,26 @@ static bool nfs_uuid_put(nfs_uuid_t *nfs_uuid)

/* Walk list of files and ensure their last references dropped */
list_for_each_entry_safe(nfl, tmp, &local_files, list) {
- nfs_close_local_fh(nfl);
+ struct nfsd_file *ro_nf;
+ struct nfsd_file *rw_nf;
+
+ ro_nf = unrcu_pointer(xchg(&nfl->ro_file, NULL));
+ rw_nf = unrcu_pointer(xchg(&nfl->rw_file, NULL));
+
+ spin_lock(&nfs_uuid->lock);
+ /* Remove nfl from nfs_uuid->files list */
+ list_del_init(&nfl->list);
+ spin_unlock(&nfs_uuid->lock);
+ /* 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);
+
cond_resched();
}

--
2.49.0