NFS: Convert struct nfs_open_context to use a kref

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/inode.c

@@ -461,7 +461,6 @@ static struct nfs_open_context *alloc_nfs_open_context(struct vfsmount *mnt, str
 
 	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
 	if (ctx != NULL) {
-		atomic_set(&ctx->count, 1);
 		ctx->path.dentry = dget(dentry);
 		ctx->path.mnt = mntget(mnt);
 		ctx->cred = get_rpccred(cred);
@@ -469,6 +468,7 @@ static struct nfs_open_context *alloc_nfs_open_context(struct vfsmount *mnt, str
 		ctx->lockowner = current->files;
 		ctx->error = 0;
 		ctx->dir_cookie = 0;
+		kref_init(&ctx->kref);
 	}
 	return ctx;
 }
@@ -476,13 +476,15 @@ static struct nfs_open_context *alloc_nfs_open_context(struct vfsmount *mnt, str
 struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx)
 {
 	if (ctx != NULL)
-		atomic_inc(&ctx->count);
+		kref_get(&ctx->kref);
 	return ctx;
 }
 
-void put_nfs_open_context(struct nfs_open_context *ctx)
+static void nfs_free_open_context(struct kref *kref)
 {
-	if (atomic_dec_and_test(&ctx->count)) {
+	struct nfs_open_context *ctx = container_of(kref,
+			struct nfs_open_context, kref);
+
 	if (!list_empty(&ctx->list)) {
 		struct inode *inode = ctx->path.dentry->d_inode;
 		spin_lock(&inode->i_lock);
@@ -496,7 +498,11 @@ void put_nfs_open_context(struct nfs_open_context *ctx)
 	dput(ctx->path.dentry);
 	mntput(ctx->path.mnt);
 	kfree(ctx);
-	}
+}
+
+void put_nfs_open_context(struct nfs_open_context *ctx)
+{
+	kref_put(&ctx->kref, nfs_free_open_context);
 }
 
 /*

include/linux/nfs_fs.h

@@ -30,6 +30,7 @@
 #ifdef __KERNEL__
 
 #include <linux/in.h>
+#include <linux/kref.h>
 #include <linux/mm.h>
 #include <linux/namei.h>
 #include <linux/pagemap.h>
@@ -70,7 +71,7 @@ struct nfs_access_entry {
 
 struct nfs4_state;
 struct nfs_open_context {
-	atomic_t count;
+	struct kref kref;
 	struct path path;
 	struct rpc_cred *cred;
 	struct nfs4_state *state;