Introduce nfsd_serv_try_get and nfsd_serv_put and update the nfsd code
to prevent nfsd_destroy_serv from destroying nn->nfsd_serv until any
caller of nfsd_serv_try_get releases their reference using nfsd_serv_put.
A percpu_ref is used to implement the interlock between
nfsd_destroy_serv and any caller of nfsd_serv_try_get.
This interlock is needed to properly wait for the completion of client
initiated localio calls to nfsd (that are _not_ in the context of nfsd).
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: NeilBrown <neilb@xxxxxxx>
---
fs/nfsd/netns.h | 8 +++++++-
fs/nfsd/nfssvc.c | 43 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+), 1 deletion(-)
diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 238fc4e56e53..1b9da8f183e3 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -13,6 +13,7 @@
#include <linux/filelock.h>
#include <linux/nfs4.h>
#include <linux/percpu_counter.h>
+#include <linux/percpu-refcount.h>
#include <linux/siphash.h>
#include <linux/sunrpc/stats.h>
@@ -139,7 +140,9 @@ struct nfsd_net {
struct svc_info nfsd_info;
#define nfsd_serv nfsd_info.serv
-
+ struct percpu_ref nfsd_serv_ref;
+ struct completion nfsd_serv_confirm_done;
+ struct completion nfsd_serv_free_done;
/*
* clientid and stateid data for construction of net unique COPY
@@ -221,6 +224,9 @@ struct nfsd_net {
extern bool nfsd_support_version(int vers);
extern unsigned int nfsd_net_id;
+bool nfsd_serv_try_get(struct net *net);
+void nfsd_serv_put(struct net *net);
+
void nfsd_copy_write_verifier(__be32 verf[2], struct nfsd_net *nn);
void nfsd_reset_write_verifier(struct nfsd_net *nn);
#endif /* __NFSD_NETNS_H__ */
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index defc430f912f..307e365798f5 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -193,6 +193,34 @@ int nfsd_minorversion(struct nfsd_net *nn, u32 minorversion, enum vers_op change
return 0;
}
+bool nfsd_serv_try_get(struct net *net)
+{
+ struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
+ return (nn && percpu_ref_tryget_live(&nn->nfsd_serv_ref));
+}
+
+void nfsd_serv_put(struct net *net)
+{
+ struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
+ percpu_ref_put(&nn->nfsd_serv_ref);
+}
+
+static void nfsd_serv_done(struct percpu_ref *ref)
+{
+ struct nfsd_net *nn = container_of(ref, struct nfsd_net, nfsd_serv_ref);
+
+ complete(&nn->nfsd_serv_confirm_done);
+}
+
+static void nfsd_serv_free(struct percpu_ref *ref)
+{
+ struct nfsd_net *nn = container_of(ref, struct nfsd_net, nfsd_serv_ref);
+
+ complete(&nn->nfsd_serv_free_done);
+}
+
/*
* Maximum number of nfsd processes
*/
@@ -392,6 +420,7 @@ static void nfsd_shutdown_net(struct net *net)
lockd_down(net);
nn->lockd_up = false;
}
+ percpu_ref_exit(&nn->nfsd_serv_ref);
nn->nfsd_net_up = false;
nfsd_shutdown_generic();
}
@@ -471,6 +500,13 @@ void nfsd_destroy_serv(struct net *net)
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
struct svc_serv *serv = nn->nfsd_serv;
+ lockdep_assert_held(&nfsd_mutex);
+
+ percpu_ref_kill_and_confirm(&nn->nfsd_serv_ref, nfsd_serv_done);
+ wait_for_completion(&nn->nfsd_serv_confirm_done);
+ wait_for_completion(&nn->nfsd_serv_free_done);
+ /* percpu_ref_exit is called in nfsd_shutdown_net */
+
spin_lock(&nfsd_notifier_lock);
nn->nfsd_serv = NULL;
spin_unlock(&nfsd_notifier_lock);
@@ -595,6 +631,13 @@ int nfsd_create_serv(struct net *net)
if (nn->nfsd_serv)
return 0;
+ error = percpu_ref_init(&nn->nfsd_serv_ref, nfsd_serv_free,
+ 0, GFP_KERNEL);
+ if (error)
+ return error;
+ init_completion(&nn->nfsd_serv_free_done);
+ init_completion(&nn->nfsd_serv_confirm_done);
+
if (nfsd_max_blksize == 0)
nfsd_max_blksize = nfsd_get_default_max_blksize();
nfsd_reset_versions(nn);
--
2.44.0
