Revert "NFS: add nfs_sb_deactive_async to avoid deadlock"

This reverts commit 324d003b.

The deadlock turned out to be caused by a workqueue limitation that has
now been worked around in the RPC code (see comment in rpc_free_task).
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/inode.c

@@ -694,10 +694,7 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
 	if (ctx->cred != NULL)
 		put_rpccred(ctx->cred);
 	dput(ctx->dentry);
-	if (is_sync)
-		nfs_sb_deactive(sb);
-	else
-		nfs_sb_deactive_async(sb);
+	nfs_sb_deactive(sb);
 	kfree(ctx->mdsthreshold);
 	kfree(ctx);
 }

fs/nfs/internal.h

@@ -329,7 +329,6 @@ extern int __init register_nfs_fs(void);
 extern void __exit unregister_nfs_fs(void);
 extern void nfs_sb_active(struct super_block *sb);
 extern void nfs_sb_deactive(struct super_block *sb);
-extern void nfs_sb_deactive_async(struct super_block *sb);
 
 /* namespace.c */
 #define NFS_PATH_CANONICAL 1

fs/nfs/nfs4proc.c

@@ -2088,7 +2088,7 @@ static void nfs4_free_closedata(void *data)
 	nfs4_put_open_state(calldata->state);
 	nfs_free_seqid(calldata->arg.seqid);
 	nfs4_put_state_owner(sp);
-	nfs_sb_deactive_async(sb);
+	nfs_sb_deactive(sb);
 	kfree(calldata);
 }
 

fs/nfs/super.c

@@ -54,7 +54,6 @@
 #include <linux/parser.h>
 #include <linux/nsproxy.h>
 #include <linux/rcupdate.h>
-#include <linux/kthread.h>
 
 #include <asm/uaccess.h>
 
@@ -418,54 +417,6 @@ void nfs_sb_deactive(struct super_block *sb)
 }
 EXPORT_SYMBOL_GPL(nfs_sb_deactive);
 
-static int nfs_deactivate_super_async_work(void *ptr)
-{
-	struct super_block *sb = ptr;
-
-	deactivate_super(sb);
-	module_put_and_exit(0);
-	return 0;
-}
-
-/*
- * same effect as deactivate_super, but will do final unmount in kthread
- * context
- */
-static void nfs_deactivate_super_async(struct super_block *sb)
-{
-	struct task_struct *task;
-	char buf[INET6_ADDRSTRLEN + 1];
-	struct nfs_server *server = NFS_SB(sb);
-	struct nfs_client *clp = server->nfs_client;
-
-	if (!atomic_add_unless(&sb->s_active, -1, 1)) {
-		rcu_read_lock();
-		snprintf(buf, sizeof(buf),
-			rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_ADDR));
-		rcu_read_unlock();
-
-		__module_get(THIS_MODULE);
-		task = kthread_run(nfs_deactivate_super_async_work, sb,
-				"%s-deactivate-super", buf);
-		if (IS_ERR(task)) {
-			pr_err("%s: kthread_run: %ld\n",
-				__func__, PTR_ERR(task));
-			/* make synchronous call and hope for the best */
-			deactivate_super(sb);
-			module_put(THIS_MODULE);
-		}
-	}
-}
-
-void nfs_sb_deactive_async(struct super_block *sb)
-{
-	struct nfs_server *server = NFS_SB(sb);
-
-	if (atomic_dec_and_test(&server->active))
-		nfs_deactivate_super_async(sb);
-}
-EXPORT_SYMBOL_GPL(nfs_sb_deactive_async);
-
 /*
  * Deliver file system statistics to userspace
  */

fs/nfs/unlink.c

@@ -95,7 +95,7 @@ static void nfs_async_unlink_release(void *calldata)
 
 	nfs_dec_sillycount(data->dir);
 	nfs_free_unlinkdata(data);
-	nfs_sb_deactive_async(sb);
+	nfs_sb_deactive(sb);
 }
 
 static void nfs_unlink_prepare(struct rpc_task *task, void *calldata)