---

yaml
---
r: 29777
b: refs/heads/master
c: 33649c9
h: refs/heads/master
i:
  29775: 3ea8cca
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7142125937e1482ad3ae4366594c6586153dfc86
+refs/heads/master: 33649c91a3df57c1090a657637d44b896de367e7

trunk/fs/fuse/dev.c

@@ -76,6 +76,13 @@ static void __fuse_put_request(struct fuse_req *req)
 	atomic_dec(&req->count);
 }
 
+static void fuse_req_init_context(struct fuse_req *req)
+{
+	req->in.h.uid = current->fsuid;
+	req->in.h.gid = current->fsgid;
+	req->in.h.pid = current->pid;
+}
+
 struct fuse_req *fuse_get_req(struct fuse_conn *fc)
 {
 	struct fuse_req *req;
@@ -100,9 +107,7 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc)
 	if (!req)
 		goto out;
 
-	req->in.h.uid = current->fsuid;
-	req->in.h.gid = current->fsgid;
-	req->in.h.pid = current->pid;
+	fuse_req_init_context(req);
 	req->waiting = 1;
 	return req;
 
@@ -111,12 +116,87 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc)
 	return ERR_PTR(err);
 }
 
+/*
+ * Return request in fuse_file->reserved_req.  However that may
+ * currently be in use.  If that is the case, wait for it to become
+ * available.
+ */
+static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
+					 struct file *file)
+{
+	struct fuse_req *req = NULL;
+	struct fuse_file *ff = file->private_data;
+
+	do {
+		wait_event(fc->blocked_waitq, ff->reserved_req);
+		spin_lock(&fc->lock);
+		if (ff->reserved_req) {
+			req = ff->reserved_req;
+			ff->reserved_req = NULL;
+			get_file(file);
+			req->stolen_file = file;
+		}
+		spin_unlock(&fc->lock);
+	} while (!req);
+
+	return req;
+}
+
+/*
+ * Put stolen request back into fuse_file->reserved_req
+ */
+static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
+{
+	struct file *file = req->stolen_file;
+	struct fuse_file *ff = file->private_data;
+
+	spin_lock(&fc->lock);
+	fuse_request_init(req);
+	BUG_ON(ff->reserved_req);
+	ff->reserved_req = req;
+	wake_up(&fc->blocked_waitq);
+	spin_unlock(&fc->lock);
+	fput(file);
+}
+
+/*
+ * Gets a requests for a file operation, always succeeds
+ *
+ * This is used for sending the FLUSH request, which must get to
+ * userspace, due to POSIX locks which may need to be unlocked.
+ *
+ * If allocation fails due to OOM, use the reserved request in
+ * fuse_file.
+ *
+ * This is very unlikely to deadlock accidentally, since the
+ * filesystem should not have it's own file open.  If deadlock is
+ * intentional, it can still be broken by "aborting" the filesystem.
+ */
+struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
+{
+	struct fuse_req *req;
+
+	atomic_inc(&fc->num_waiting);
+	wait_event(fc->blocked_waitq, !fc->blocked);
+	req = fuse_request_alloc();
+	if (!req)
+		req = get_reserved_req(fc, file);
+
+	fuse_req_init_context(req);
+	req->waiting = 1;
+	return req;
+}
+
 void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
 {
 	if (atomic_dec_and_test(&req->count)) {
 		if (req->waiting)
 			atomic_dec(&fc->num_waiting);
-		fuse_request_free(req);
+
+		if (req->stolen_file)
+			put_reserved_req(fc, req);
+		else
+			fuse_request_free(req);
 	}
 }
 

trunk/fs/fuse/file.c

@@ -48,8 +48,8 @@ struct fuse_file *fuse_file_alloc(void)
 	struct fuse_file *ff;
 	ff = kmalloc(sizeof(struct fuse_file), GFP_KERNEL);
 	if (ff) {
-		ff->release_req = fuse_request_alloc();
-		if (!ff->release_req) {
+		ff->reserved_req = fuse_request_alloc();
+		if (!ff->reserved_req) {
 			kfree(ff);
 			ff = NULL;
 		}
@@ -59,7 +59,7 @@ struct fuse_file *fuse_file_alloc(void)
 
 void fuse_file_free(struct fuse_file *ff)
 {
-	fuse_request_free(ff->release_req);
+	fuse_request_free(ff->reserved_req);
 	kfree(ff);
 }
 
@@ -115,7 +115,7 @@ int fuse_open_common(struct inode *inode, struct file *file, int isdir)
 struct fuse_req *fuse_release_fill(struct fuse_file *ff, u64 nodeid, int flags,
 				   int opcode)
 {
-	struct fuse_req *req = ff->release_req;
+	struct fuse_req *req = ff->reserved_req;
 	struct fuse_release_in *inarg = &req->misc.release_in;
 
 	inarg->fh = ff->fh;
@@ -187,10 +187,7 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 	if (fc->no_flush)
 		return 0;
 
-	req = fuse_get_req(fc);
-	if (IS_ERR(req))
-		return PTR_ERR(req);
-
+	req = fuse_get_req_nofail(fc, file);
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.fh = ff->fh;
 	inarg.lock_owner = fuse_lock_owner_id(id);

trunk/fs/fuse/fuse_i.h

@@ -65,7 +65,7 @@ struct fuse_inode {
 /** FUSE specific file data */
 struct fuse_file {
 	/** Request reserved for flush and release */
-	struct fuse_req *release_req;
+	struct fuse_req *reserved_req;
 
 	/** File handle used by userspace */
 	u64 fh;
@@ -213,6 +213,9 @@ struct fuse_req {
 
 	/** Request completion callback */
 	void (*end)(struct fuse_conn *, struct fuse_req *);
+
+	/** Request is stolen from fuse_file->reserved_req */
+	struct file *stolen_file;
 };
 
 /**
@@ -456,10 +459,15 @@ struct fuse_req *fuse_request_alloc(void);
 void fuse_request_free(struct fuse_req *req);
 
 /**
- * Reserve a preallocated request
+ * Get a request, may fail with -ENOMEM
  */
 struct fuse_req *fuse_get_req(struct fuse_conn *fc);
 
+/**
+ * Gets a requests for a file operation, always succeeds
+ */
+struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file);
+
 /**
  * Decrement reference count of a request.  If count goes to zero free
  * the request.