ecryptfs: don't reinvent the wheels, please - use struct completion

... and keep the sodding requests on stack - they are small enough.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ecryptfs/ecryptfs_kernel.h

@@ -550,20 +550,6 @@ extern struct kmem_cache *ecryptfs_key_record_cache;
 extern struct kmem_cache *ecryptfs_key_sig_cache;
 extern struct kmem_cache *ecryptfs_global_auth_tok_cache;
 extern struct kmem_cache *ecryptfs_key_tfm_cache;
-extern struct kmem_cache *ecryptfs_open_req_cache;
-
-struct ecryptfs_open_req {
-#define ECRYPTFS_REQ_PROCESSED 0x00000001
-#define ECRYPTFS_REQ_DROPPED   0x00000002
-#define ECRYPTFS_REQ_ZOMBIE    0x00000004
-	u32 flags;
-	struct file **lower_file;
-	struct dentry *lower_dentry;
-	struct vfsmount *lower_mnt;
-	wait_queue_head_t wait;
-	struct mutex mux;
-	struct list_head kthread_ctl_list;
-};
 
 struct inode *ecryptfs_get_inode(struct inode *lower_inode,
 				 struct super_block *sb);

fs/ecryptfs/kthread.c

@@ -27,7 +27,13 @@
 #include <linux/mount.h>
 #include "ecryptfs_kernel.h"
 
-struct kmem_cache *ecryptfs_open_req_cache;
+struct ecryptfs_open_req {
+	struct file **lower_file;
+	struct dentry *lower_dentry;
+	struct vfsmount *lower_mnt;
+	struct completion done;
+	struct list_head kthread_ctl_list;
+};
 
 static struct ecryptfs_kthread_ctl {
 #define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001
@@ -67,18 +73,13 @@ static int ecryptfs_threadfn(void *ignored)
 			req = list_first_entry(&ecryptfs_kthread_ctl.req_list,
 					       struct ecryptfs_open_req,
 					       kthread_ctl_list);
-			mutex_lock(&req->mux);
 			list_del(&req->kthread_ctl_list);
-			if (!(req->flags & ECRYPTFS_REQ_ZOMBIE)) {
-				dget(req->lower_dentry);
-				mntget(req->lower_mnt);
-				(*req->lower_file) = dentry_open(
-					req->lower_dentry, req->lower_mnt,
-					(O_RDWR | O_LARGEFILE), current_cred());
-				req->flags |= ECRYPTFS_REQ_PROCESSED;
-			}
-			wake_up(&req->wait);
-			mutex_unlock(&req->mux);
+			dget(req->lower_dentry);
+			mntget(req->lower_mnt);
+			(*req->lower_file) = dentry_open(
+				req->lower_dentry, req->lower_mnt,
+				(O_RDWR | O_LARGEFILE), current_cred());
+			complete(&req->done);
 		}
 		mutex_unlock(&ecryptfs_kthread_ctl.mux);
 	}
@@ -111,10 +112,9 @@ void ecryptfs_destroy_kthread(void)
 	ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE;
 	list_for_each_entry(req, &ecryptfs_kthread_ctl.req_list,
 			    kthread_ctl_list) {
-		mutex_lock(&req->mux);
-		req->flags |= ECRYPTFS_REQ_ZOMBIE;
-		wake_up(&req->wait);
-		mutex_unlock(&req->mux);
+		list_del(&req->kthread_ctl_list);
+		*req->lower_file = ERR_PTR(-EIO);
+		complete(&req->done);
 	}
 	mutex_unlock(&ecryptfs_kthread_ctl.mux);
 	kthread_stop(ecryptfs_kthread);
@@ -136,7 +136,7 @@ int ecryptfs_privileged_open(struct file **lower_file,
 			     struct vfsmount *lower_mnt,
 			     const struct cred *cred)
 {
-	struct ecryptfs_open_req *req;
+	struct ecryptfs_open_req req;
 	int flags = O_LARGEFILE;
 	int rc = 0;
 
@@ -153,17 +153,10 @@ int ecryptfs_privileged_open(struct file **lower_file,
 		rc = PTR_ERR((*lower_file));
 		goto out;
 	}
-	req = kmem_cache_alloc(ecryptfs_open_req_cache, GFP_KERNEL);
-	if (!req) {
-		rc = -ENOMEM;
-		goto out;
-	}
-	mutex_init(&req->mux);
-	req->lower_file = lower_file;
-	req->lower_dentry = lower_dentry;
-	req->lower_mnt = lower_mnt;
-	init_waitqueue_head(&req->wait);
-	req->flags = 0;
+	init_completion(&req.done);
+	req.lower_file = lower_file;
+	req.lower_dentry = lower_dentry;
+	req.lower_mnt = lower_mnt;
 	mutex_lock(&ecryptfs_kthread_ctl.mux);
 	if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
 		rc = -EIO;
@@ -171,27 +164,14 @@ int ecryptfs_privileged_open(struct file **lower_file,
 		printk(KERN_ERR "%s: We are in the middle of shutting down; "
 		       "aborting privileged request to open lower file\n",
 			__func__);
-		goto out_free;
+		goto out;
 	}
-	list_add_tail(&req->kthread_ctl_list, &ecryptfs_kthread_ctl.req_list);
+	list_add_tail(&req.kthread_ctl_list, &ecryptfs_kthread_ctl.req_list);
 	mutex_unlock(&ecryptfs_kthread_ctl.mux);
 	wake_up(&ecryptfs_kthread_ctl.wait);
-	wait_event(req->wait, (req->flags != 0));
-	mutex_lock(&req->mux);
-	BUG_ON(req->flags == 0);
-	if (req->flags & ECRYPTFS_REQ_DROPPED
-	    || req->flags & ECRYPTFS_REQ_ZOMBIE) {
-		rc = -EIO;
-		printk(KERN_WARNING "%s: Privileged open request dropped\n",
-		       __func__);
-		goto out_unlock;
-	}
-	if (IS_ERR(*req->lower_file))
-		rc = PTR_ERR(*req->lower_file);
-out_unlock:
-	mutex_unlock(&req->mux);
-out_free:
-	kmem_cache_free(ecryptfs_open_req_cache, req);
+	wait_for_completion(&req.done);
+	if (IS_ERR(*lower_file))
+		rc = PTR_ERR(*lower_file);
 out:
 	return rc;
 }

fs/ecryptfs/main.c

@@ -681,11 +681,6 @@ static struct ecryptfs_cache_info {
 		.name = "ecryptfs_key_tfm_cache",
 		.size = sizeof(struct ecryptfs_key_tfm),
 	},
-	{
-		.cache = &ecryptfs_open_req_cache,
-		.name = "ecryptfs_open_req_cache",
-		.size = sizeof(struct ecryptfs_open_req),
-	},
 };
 
 static void ecryptfs_free_kmem_caches(void)