From: Ian Kent <ikent@redhat.com>
Date: Tue, 1 Dec 2009 17:07:46 -0500
Subject: [nfs] add an nfsiod workqueue
Message-id: <20091201170746.12228.18836.stgit@zeus.themaw.net>
Patchwork-id: 21575
O-Subject: [RHEL 5.4 PATCH 5/5] NFS: Add an nfsiod workqueue (bz489931)
Bugzilla: 489931
RH-Acked-by: Jeff Layton <jlayton@redhat.com>

From: Trond Myklebust <Trond.Myklebust@netapp.com>

NFS post-rpciod cleanups often involve tasks that cannot be safely
performed within the rpciod context (due to deadlock concerns). We
therefore add a dedicated NFS workqueue that can perform tasks like
cleaning up state after an interrupted NFSv4 open() call, or calling
put_nfs_open_context() after an asynchronous read or write call.

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

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 795339a..863c29b 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1170,6 +1170,36 @@ static void nfs_destroy_inodecache(void)
 		printk(KERN_INFO "nfs_inode_cache: not all structures were freed\n");
 }
 
+struct workqueue_struct *nfsiod_workqueue;
+
+/*
+ * start up the nfsiod workqueue
+ */
+static int nfsiod_start(void)
+{
+	struct workqueue_struct *wq;
+	dprintk("RPC:       creating workqueue nfsiod\n");
+	wq = create_singlethread_workqueue("nfsiod");
+	if (wq == NULL)
+		return -ENOMEM;
+	nfsiod_workqueue = wq;
+	return 0;
+}
+
+/*
+ * Destroy the nfsiod workqueue
+ */
+static void nfsiod_stop(void)
+{
+	struct workqueue_struct *wq;
+
+	wq = nfsiod_workqueue;
+	if (wq == NULL)
+		return;
+	nfsiod_workqueue = NULL;
+	destroy_workqueue(wq);
+}
+
 /*
  * Initialize NFS
  */
@@ -1177,6 +1207,10 @@ static int __init init_nfs_fs(void)
 {
 	int err;
 
+	err = nfsiod_start();
+	if (err)
+		goto out6;
+
 	err = nfs_fs_proc_init();
 	if (err)
 		goto out5;
@@ -1223,6 +1257,8 @@ out3:
 out4:
 	nfs_fs_proc_exit();
 out5:
+	nfsiod_stop();
+out6:
 	return err;
 }
 
@@ -1238,6 +1274,7 @@ static void __exit exit_nfs_fs(void)
 #endif
 	unregister_nfs_fs();
 	nfs_fs_proc_exit();
+	nfsiod_stop();
 }
 
 /* Not quite true; I just maintain it */
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 83f8fc2..e9db77d 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -146,6 +146,7 @@ extern int nfs4_proc_fs_locations(struct inode *dir, struct dentry *dentry,
 extern int nfs_access_cache_shrinker(int nr_to_scan, gfp_t gfp_mask);
 
 /* inode.c */
+extern struct workqueue_struct *nfsiod_workqueue;
 extern struct inode *nfs_alloc_inode(struct super_block *sb);
 extern void nfs_destroy_inode(struct inode *);
 extern int nfs_write_inode(struct inode *,int);