nfs_common: track all open nfsd_files per LOCALIO nfs_client

This tracking enables __nfsd_file_cache_purge() to call
nfs_localio_invalidate_clients(), upon shutdown or export change, to
nfs_close_local_fh() all open nfsd_files that are still cached by the
LOCALIO nfs clients associated with nfsd_net that is being shutdown.

Now that the client must track all open nfsd_files there was more work
than necessary being done with the global nfs_uuids_lock contended.
This manifested in various RCU issues, e.g.:
 hrtimer: interrupt took 47969440 ns
 rcu: INFO: rcu_sched detected stalls on CPUs/tasks:

Use nfs_uuid->lock to protect all nfs_uuid_t members, instead of
nfs_uuids_lock, once nfs_uuid_is_local() adds the client to
nn->local_clients.

Also add 'local_clients_lock' to 'struct nfsd_net' to protect
nn->local_clients.  And store a pointer to spinlock in the 'list_lock'
member of nfs_uuid_t so nfs_localio_disable_client() can use it to
avoid taking the global nfs_uuids_lock.

In combination, these split out locks eliminate the use of the single
nfslocalio.c global nfs_uuids_lock in the IO paths (open and close).

Also refactored associated fs/nfs_common/nfslocalio.c methods' locking
to reduce work performed with spinlocks held in general.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h
index aa2b5c6561ab..c68a529230c1 100644
--- a/include/linux/nfslocalio.h
+++ b/include/linux/nfslocalio.h
@@ -30,19 +30,23 @@ typedef struct {
 	/* sadly this struct is just over a cacheline, avoid bouncing */
 	spinlock_t ____cacheline_aligned lock;
 	struct list_head list;
+	spinlock_t *list_lock; /* nn->local_clients_lock */
 	struct net __rcu *net; /* nfsd's network namespace */
 	struct auth_domain *dom; /* auth_domain for localio */
+	/* Local files to close when net is shut down or exports change */
+	struct list_head files;
 } nfs_uuid_t;
 
 void nfs_uuid_init(nfs_uuid_t *);
 bool nfs_uuid_begin(nfs_uuid_t *);
 void nfs_uuid_end(nfs_uuid_t *);
-void nfs_uuid_is_local(const uuid_t *, struct list_head *,
+void nfs_uuid_is_local(const uuid_t *, struct list_head *, spinlock_t *,
 		       struct net *, struct auth_domain *, struct module *);
 
 void nfs_localio_enable_client(struct nfs_client *clp);
 void nfs_localio_disable_client(struct nfs_client *clp);
-void nfs_localio_invalidate_clients(struct list_head *list);
+void nfs_localio_invalidate_clients(struct list_head *nn_local_clients,
+				    spinlock_t *nn_local_clients_lock);
 
 /* localio needs to map filehandle -> struct nfsd_file */
 extern struct nfsd_file *