Add DESTROY message

ChangeLog

@@ -19,6 +19,15 @@
 
 	* Minor clean up of udev rules
 
+	* Add a synchronous DESTROY message to kernel interface.  This is
+	invoked from umount, when the final instance of the filesystem is
+	released.  It is only sent for filesystems mounted with the
+	'blkdev' option for security reasons.
+
+	* If the DESTROY message is received, call the filesystem's
+	->destroy() method.  In this case it's not called from session
+	destruction as it would be otherwise.
+
 2006-10-01  Miklos Szeredi <miklos@szeredi.hu>
 
 	* Released 2.6.0-rc2

kernel/fuse_i.h

@@ -357,6 +357,9 @@ struct fuse_conn {
 	    reply, before any other request, and never cleared */
 	unsigned conn_error : 1;
 
+	/** Connection successful.  Only set in INIT */
+	unsigned conn_init : 1;
+
 	/** Do readpages asynchronously?  Only set in INIT */
 	unsigned async_read : 1;
 
@@ -427,6 +430,9 @@ struct fuse_conn {
 
 	/** Key for lock owner ID scrambling */
 	u32 scramble_key[4];
+
+	/** Reserved request for the DESTROY message */
+	struct fuse_req *destroy_req;
 };
 
 static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)

kernel/fuse_kernel.h

@@ -168,6 +168,7 @@ enum fuse_opcode {
 	FUSE_CREATE        = 35,
 	FUSE_INTERRUPT     = 36,
 	FUSE_BMAP          = 37,
+	FUSE_DESTROY       = 38,
 };
 
 /* The read buffer is required to be at least 8k, but may be much larger */

kernel/inode.c

@@ -226,10 +226,23 @@ static void fuse_umount_begin(struct super_block *sb)
 }
 #endif
 
+static void fuse_send_destroy(struct fuse_conn *fc)
+{
+	struct fuse_req *req = fc->destroy_req;
+	if (req && fc->conn_init) {
+		fc->destroy_req = NULL;
+		req->in.h.opcode = FUSE_DESTROY;
+		req->force = 1;
+		request_send(fc, req);
+		fuse_put_request(fc, req);
+	}
+}
+
 static void fuse_put_super(struct super_block *sb)
 {
 	struct fuse_conn *fc = get_fuse_conn_super(sb);
 
+	fuse_send_destroy(fc);
 	spin_lock(&fc->lock);
 	fc->connected = 0;
 	fc->blocked = 0;
@@ -447,6 +460,8 @@ static struct fuse_conn *new_conn(void)
 void fuse_conn_put(struct fuse_conn *fc)
 {
 	if (atomic_dec_and_test(&fc->count)) {
+		if (fc->destroy_req)
+			fuse_request_free(fc->destroy_req);
 		mutex_destroy(&fc->inst_mutex);
 		kfree(fc);
 	}
@@ -565,6 +580,7 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 		fc->bdi.ra_pages = min(fc->bdi.ra_pages, ra_pages);
 		fc->minor = arg->minor;
 		fc->max_write = arg->minor < 5 ? 4096 : arg->max_write;
+		fc->conn_init = 1;
 	}
 	fuse_put_request(fc, req);
 	fc->blocked = 0;
@@ -665,6 +681,12 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	if (!init_req)
 		goto err_put_root;
 
+	if (is_bdev) {
+		fc->destroy_req = fuse_request_alloc();
+		if (!fc->destroy_req)
+			goto err_put_root;
+	}
+
 	mutex_lock(&fuse_mutex);
 	err = -EINVAL;
 	if (file->private_data)

lib/fuse_lowlevel.c

@@ -57,6 +57,7 @@ struct fuse_ll {
     struct fuse_req list;
     struct fuse_req interrupts;
     pthread_mutex_t lock;
+    int got_destroy;
 };
 
 static void convert_stat(const struct stat *stbuf, struct fuse_attr *attr)
@@ -995,6 +996,20 @@ static void do_init(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)
     send_reply_ok(req, &outarg, arg->minor < 5 ? 8 : sizeof(outarg));
 }
 
+static void do_destroy(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)
+{
+    struct fuse_ll *f = req->f;
+
+    (void) nodeid;
+    (void) inarg;
+
+    f->got_destroy = 1;
+    if (f->op.destroy)
+        f->op.destroy(f->userdata);
+
+    send_reply_ok(req, NULL, 0);
+}
+
 void *fuse_req_userdata(fuse_req_t req)
 {
     return req->f->userdata;
@@ -1066,6 +1081,7 @@ static struct {
     [FUSE_CREATE]      = { do_create,      "CREATE"      },
     [FUSE_INTERRUPT]   = { do_interrupt,   "INTERRUPT"   },
     [FUSE_BMAP]        = { do_bmap,        "BMAP"        },
+    [FUSE_DESTROY]     = { do_destroy,     "DESTROY"     },
 };
 
 #define FUSE_MAXOP (sizeof(fuse_ll_ops) / sizeof(fuse_ll_ops[0]))
@@ -1200,8 +1216,10 @@ static void fuse_ll_destroy(void *data)
 {
     struct fuse_ll *f = (struct fuse_ll *) data;
 
-    if (f->op.destroy)
-        f->op.destroy(f->userdata);
+    if (f->got_init && !f->got_destroy) {
+        if (f->op.destroy)
+            f->op.destroy(f->userdata);
+    }
 
     pthread_mutex_destroy(&f->lock);
     free(f);