[PATCH] nfsd4: reference count stateowners

Reference-counting the nfsd4 stateowner structs will let us fix a race and
simplify some of the xdr code a bit, and may also help us make the nfsd4
locking a little more fine-grained in the future.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/nfs4state.c

@@ -833,6 +833,17 @@ release_all_files(void)
 	}
 }
 
+/* should use a slab cache */
+void
+nfs4_free_stateowner(struct kref *kref)
+{
+	struct nfs4_stateowner *sop =
+		container_of(kref, struct nfs4_stateowner, so_ref);
+	kfree(sop->so_owner.data);
+	kfree(sop);
+	free_sowner++;
+}
+
 static inline struct nfs4_stateowner *
 alloc_stateowner(struct xdr_netobj *owner)
 {
@@ -842,6 +853,7 @@ alloc_stateowner(struct xdr_netobj *owner)
 		if ((sop->so_owner.data = kmalloc(owner->len, GFP_KERNEL))) {
 			memcpy(sop->so_owner.data, owner->data, owner->len);
 			sop->so_owner.len = owner->len;
+			kref_init(&sop->so_ref);
 			return sop;
 		} 
 		kfree(sop);
@@ -849,17 +861,6 @@ alloc_stateowner(struct xdr_netobj *owner)
 	return NULL;
 }
 
-/* should use a slab cache */
-static void
-free_stateowner(struct nfs4_stateowner *sop) {
-	if (sop) {
-		kfree(sop->so_owner.data);
-		kfree(sop);
-		sop = NULL;
-		free_sowner++;
-	}
-}
-
 static struct nfs4_stateowner *
 alloc_init_open_stateowner(unsigned int strhashval, struct nfs4_client *clp, struct nfsd4_open *open) {
 	struct nfs4_stateowner *sop;
@@ -932,7 +933,7 @@ release_stateowner(struct nfs4_stateowner *sop)
 {
 	unhash_stateowner(sop);
 	list_del(&sop->so_close_lru);
-	free_stateowner(sop);
+	nfs4_put_stateowner(sop);
 }
 
 static inline void
@@ -1460,7 +1461,7 @@ nfs4_laundromat(void)
 		dprintk("NFSD: purging unused open stateowner (so_id %d)\n",
 			sop->so_id);
 		list_del(&sop->so_close_lru);
-		free_stateowner(sop);
+		nfs4_put_stateowner(sop);
 	}
 	if (clientid_val < NFSD_LAUNDROMAT_MINTIMEOUT)
 		clientid_val = NFSD_LAUNDROMAT_MINTIMEOUT;

include/linux/nfsd/state.h

@@ -38,6 +38,7 @@
 #define _NFSD4_STATE_H
 
 #include <linux/list.h>
+#include <linux/kref.h>
 #include <linux/sunrpc/clnt.h>
 
 #define NFS4_OPAQUE_LIMIT 1024
@@ -168,6 +169,7 @@ struct nfs4_replay {
 *         reaped by laundramat thread after lease period.
 */
 struct nfs4_stateowner {
+	struct kref		so_ref;
 	struct list_head        so_idhash;   /* hash by so_id */
 	struct list_head        so_strhash;   /* hash by op_name */
 	struct list_head        so_perclient; /* nfs4_client->cl_perclient */
@@ -248,4 +250,18 @@ extern void nfs4_lock_state(void);
 extern void nfs4_unlock_state(void);
 extern int nfs4_in_grace(void);
 extern int nfs4_check_open_reclaim(clientid_t *clid);
+extern void nfs4_free_stateowner(struct kref *kref);
+
+static inline void
+nfs4_put_stateowner(struct nfs4_stateowner *so)
+{
+	kref_put(&so->so_ref, nfs4_free_stateowner);
+}
+
+static inline void
+nfs4_get_stateowner(struct nfs4_stateowner *so)
+{
+	kref_get(&so->so_ref);
+}
+
 #endif   /* NFSD4_STATE_H */