[PATCH] FUSE - device functions

This adds the FUSE device handling functions.

This contains the following files:

 o dev.c
    - fuse device operations (read, write, release, poll)
    - registers misc device
    - support for sending requests to userspace
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/fuse/Makefile

@@ -4,4 +4,4 @@
 
 obj-$(CONFIG_FUSE_FS) += fuse.o
 
-fuse-objs := inode.o
+fuse-objs := dev.o inode.o

fs/fuse/fuse_i.h

@@ -15,6 +15,12 @@
 #include <linux/backing-dev.h>
 #include <asm/semaphore.h>
 
+/** Max number of pages that can be used in a single read request */
+#define FUSE_MAX_PAGES_PER_REQ 32
+
+/** If more requests are outstanding, then the operation will block */
+#define FUSE_MAX_OUTSTANDING 10
+
 /** FUSE inode */
 struct fuse_inode {
 	/** Inode data */
@@ -28,6 +34,123 @@ struct fuse_inode {
 	unsigned long i_time;
 };
 
+/** One input argument of a request */
+struct fuse_in_arg {
+	unsigned size;
+	const void *value;
+};
+
+/** The request input */
+struct fuse_in {
+	/** The request header */
+	struct fuse_in_header h;
+
+	/** True if the data for the last argument is in req->pages */
+	unsigned argpages:1;
+
+	/** Number of arguments */
+	unsigned numargs;
+
+	/** Array of arguments */
+	struct fuse_in_arg args[3];
+};
+
+/** One output argument of a request */
+struct fuse_arg {
+	unsigned size;
+	void *value;
+};
+
+/** The request output */
+struct fuse_out {
+	/** Header returned from userspace */
+	struct fuse_out_header h;
+
+	/** Last argument is variable length (can be shorter than
+	    arg->size) */
+	unsigned argvar:1;
+
+	/** Last argument is a list of pages to copy data to */
+	unsigned argpages:1;
+
+	/** Zero partially or not copied pages */
+	unsigned page_zeroing:1;
+
+	/** Number or arguments */
+	unsigned numargs;
+
+	/** Array of arguments */
+	struct fuse_arg args[3];
+};
+
+struct fuse_req;
+struct fuse_conn;
+
+/**
+ * A request to the client
+ */
+struct fuse_req {
+	/** This can be on either unused_list, pending or processing
+	    lists in fuse_conn */
+	struct list_head list;
+
+	/** refcount */
+	atomic_t count;
+
+	/** True if the request has reply */
+	unsigned isreply:1;
+
+	/** The request is preallocated */
+	unsigned preallocated:1;
+
+	/** The request was interrupted */
+	unsigned interrupted:1;
+
+	/** Request is sent in the background */
+	unsigned background:1;
+
+	/** Data is being copied to/from the request */
+	unsigned locked:1;
+
+	/** Request has been sent to userspace */
+	unsigned sent:1;
+
+	/** The request is finished */
+	unsigned finished:1;
+
+	/** The request input */
+	struct fuse_in in;
+
+	/** The request output */
+	struct fuse_out out;
+
+	/** Used to wake up the task waiting for completion of request*/
+	wait_queue_head_t waitq;
+
+	/** Data for asynchronous requests */
+	union {
+		struct fuse_init_in_out init_in_out;
+	} misc;
+
+	/** page vector */
+	struct page *pages[FUSE_MAX_PAGES_PER_REQ];
+
+	/** number of pages in vector */
+	unsigned num_pages;
+
+	/** offset of data on first page */
+	unsigned page_offset;
+
+	/** Inode used in the request */
+	struct inode *inode;
+
+	/** Second inode used in the request (or NULL) */
+	struct inode *inode2;
+
+	/** File used in the request (or NULL) */
+	struct file *file;
+};
+
 /**
  * A Fuse connection.
  *
@@ -39,9 +162,37 @@ struct fuse_conn {
 	/** The superblock of the mounted filesystem */
 	struct super_block *sb;
 
+	/** The opened client device */
+	struct file *file;
+
 	/** The user id for this mount */
 	uid_t user_id;
 
+	/** Readers of the connection are waiting on this */
+	wait_queue_head_t waitq;
+
+	/** The list of pending requests */
+	struct list_head pending;
+
+	/** The list of requests being processed */
+	struct list_head processing;
+
+	/** Controls the maximum number of outstanding requests */
+	struct semaphore outstanding_sem;
+
+	/** This counts the number of outstanding requests if
+	    outstanding_sem would go negative */
+	unsigned outstanding_debt;
+
+	/** The list of unused requests */
+	struct list_head unused_list;
+
+	/** The next unique request id */
+	u64 reqctr;
+
+	/** Connection failed (version mismatch) */
+	unsigned conn_error : 1;
+
 	/** Backing dev info */
 	struct backing_dev_info bdi;
 };
@@ -71,13 +222,20 @@ static inline u64 get_node_id(struct inode *inode)
 	return get_fuse_inode(inode)->nodeid;
 }
 
+/** Device operations */
+extern struct file_operations fuse_dev_operations;
+
 /**
  * This is the single global spinlock which protects FUSE's structures
  *
  * The following data is protected by this lock:
  *
+ *  - the private_data field of the device file
  *  - the s_fs_info field of the super block
+ *  - unused_list, pending, processing lists in fuse_conn
+ *  - the unique request ID counter reqctr in fuse_conn
  *  - the sb (super_block) field in fuse_conn
+ *  - the file (device file) field in fuse_conn
  */
 extern spinlock_t fuse_lock;
 
@@ -87,3 +245,68 @@ extern spinlock_t fuse_lock;
  */
 void fuse_release_conn(struct fuse_conn *fc);
 
+/**
+ * Initialize the client device
+ */
+int fuse_dev_init(void);
+
+/**
+ * Cleanup the client device
+ */
+void fuse_dev_cleanup(void);
+
+/**
+ * Allocate a request
+ */
+struct fuse_req *fuse_request_alloc(void);
+
+/**
+ * Free a request
+ */
+void fuse_request_free(struct fuse_req *req);
+
+/**
+ * Reinitialize a request, the preallocated flag is left unmodified
+ */
+void fuse_reset_request(struct fuse_req *req);
+
+/**
+ * Reserve a preallocated request
+ */
+struct fuse_req *fuse_get_request(struct fuse_conn *fc);
+
+/**
+ * Reserve a preallocated request, only interruptible by SIGKILL
+ */
+struct fuse_req *fuse_get_request_nonint(struct fuse_conn *fc);
+
+/**
+ * Decrement reference count of a request.  If count goes to zero put
+ * on unused list (preallocated) or free reqest (not preallocated).
+ */
+void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req);
+
+/**
+ * Send a request (synchronous, interruptible)
+ */
+void request_send(struct fuse_conn *fc, struct fuse_req *req);
+
+/**
+ * Send a request (synchronous, non-interruptible except by SIGKILL)
+ */
+void request_send_nonint(struct fuse_conn *fc, struct fuse_req *req);
+
+/**
+ * Send a request with no reply
+ */
+void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req);
+
+/**
+ * Send a request in the background
+ */
+void request_send_background(struct fuse_conn *fc, struct fuse_req *req);
+
+/**
+ * Send the INIT message
+ */
+void fuse_send_init(struct fuse_conn *fc);

fs/fuse/inode.c

@@ -151,6 +151,8 @@ static void fuse_put_super(struct super_block *sb)
 	mount_count --;
 	fc->sb = NULL;
 	fc->user_id = 0;
+	/* Flush all readers on this fs */
+	wake_up_all(&fc->waitq);
 	fuse_release_conn(fc);
 	*get_fuse_conn_super_p(sb) = NULL;
 	spin_unlock(&fuse_lock);
@@ -229,22 +231,51 @@ static int fuse_show_options(struct seq_file *m, struct vfsmount *mnt)
 	return 0;
 }
 
-void fuse_release_conn(struct fuse_conn *fc)
+static void free_conn(struct fuse_conn *fc)
 {
+	while (!list_empty(&fc->unused_list)) {
+		struct fuse_req *req;
+		req = list_entry(fc->unused_list.next, struct fuse_req, list);
+		list_del(&req->list);
+		fuse_request_free(req);
+	}
 	kfree(fc);
 }
 
+/* Must be called with the fuse lock held */
+void fuse_release_conn(struct fuse_conn *fc)
+{
+	if (!fc->sb && !fc->file)
+		free_conn(fc);
+}
+
 static struct fuse_conn *new_conn(void)
 {
 	struct fuse_conn *fc;
 
 	fc = kmalloc(sizeof(*fc), GFP_KERNEL);
 	if (fc != NULL) {
+		int i;
 		memset(fc, 0, sizeof(*fc));
 		fc->sb = NULL;
+		fc->file = NULL;
 		fc->user_id = 0;
+		init_waitqueue_head(&fc->waitq);
+		INIT_LIST_HEAD(&fc->pending);
+		INIT_LIST_HEAD(&fc->processing);
+		INIT_LIST_HEAD(&fc->unused_list);
+		sema_init(&fc->outstanding_sem, 0);
+		for (i = 0; i < FUSE_MAX_OUTSTANDING; i++) {
+			struct fuse_req *req = fuse_request_alloc();
+			if (!req) {
+				free_conn(fc);
+				return NULL;
+			}
+			list_add(&req->list, &fc->unused_list);
+		}
 		fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 		fc->bdi.unplug_io_fn = default_unplug_io_fn;
+		fc->reqctr = 0;
 	}
 	return fc;
 }
@@ -253,11 +284,20 @@ static struct fuse_conn *get_conn(struct file *file, struct super_block *sb)
 {
 	struct fuse_conn *fc;
 
+	if (file->f_op != &fuse_dev_operations)
+		return ERR_PTR(-EINVAL);
 	fc = new_conn();
 	if (fc == NULL)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	spin_lock(&fuse_lock);
-	fc->sb = sb;
+	if (file->private_data) {
+		free_conn(fc);
+		fc = ERR_PTR(-EINVAL);
+	} else {
+		file->private_data = fc;
+		fc->sb = sb;
+		fc->file = file;
+	}
 	spin_unlock(&fuse_lock);
 	return fc;
 }
@@ -315,8 +355,8 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 
 	fc = get_conn(file, sb);
 	fput(file);
-	if (fc == NULL)
-		return -EINVAL;
+	if (IS_ERR(fc))
+		return PTR_ERR(fc);
 
 	fc->user_id = d.user_id;
 
@@ -336,6 +376,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 		iput(root);
 		goto err;
 	}
+	fuse_send_init(fc);
 	return 0;
 
  err:
@@ -411,8 +452,14 @@ static int __init fuse_init(void)
 	if (res)
 		goto err;
 
+	res = fuse_dev_init();
+	if (res)
+		goto err_fs_cleanup;
+
 	return 0;
 
+ err_fs_cleanup:
+	fuse_fs_cleanup();
  err:
 	return res;
 }
@@ -422,6 +469,7 @@ static void __exit fuse_exit(void)
 	printk(KERN_DEBUG "fuse exit\n");
 
 	fuse_fs_cleanup();
+	fuse_dev_cleanup();
 }
 
 module_init(fuse_init);

include/linux/fuse.h

@@ -11,7 +11,7 @@
 #include <asm/types.h>
 
 /** Version number of this interface */
-#define FUSE_KERNEL_VERSION 5
+#define FUSE_KERNEL_VERSION 6
 
 /** Minor version number of this interface */
 #define FUSE_KERNEL_MINOR_VERSION 1
@@ -19,6 +19,12 @@
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
 
+/** The major number of the fuse character device */
+#define FUSE_MAJOR 10
+
+/** The minor number of the fuse character device */
+#define FUSE_MINOR 229
+
 struct fuse_attr {
 	__u64	ino;
 	__u64	size;
@@ -36,3 +42,31 @@ struct fuse_attr {
 	__u32	rdev;
 };
 
+enum fuse_opcode {
+	FUSE_INIT          = 26
+};
+
+/* Conservative buffer size for the client */
+#define FUSE_MAX_IN 8192
+
+struct fuse_init_in_out {
+	__u32	major;
+	__u32	minor;
+};
+
+struct fuse_in_header {
+	__u32	len;
+	__u32	opcode;
+	__u64	unique;
+	__u64	nodeid;
+	__u32	uid;
+	__u32	gid;
+	__u32	pid;
+};
+
+struct fuse_out_header {
+	__u32	len;
+	__s32	error;
+	__u64	unique;
+};
+