fuse: add file kernel handle

The file handle, fuse_file->fh, is opaque value supplied by userland
FUSE server and uniqueness is not guaranteed.  Add file kernel handle,
fuse_file->kh, which is allocated by the kernel on file allocation and
guaranteed to be unique.

This will be used by poll to match notification to the respective file
but can be used for other purposes where unique file handle is
necessary.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

fs/fuse/dir.c

@@ -408,7 +408,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
 		goto out_put_forget_req;
 
 	err = -ENOMEM;
-	ff = fuse_file_alloc();
+	ff = fuse_file_alloc(fc);
 	if (!ff)
 		goto out_put_request;
 

fs/fuse/file.c

@@ -46,7 +46,7 @@ static int fuse_send_open(struct inode *inode, struct file *file, int isdir,
 	return err;
 }
 
-struct fuse_file *fuse_file_alloc(void)
+struct fuse_file *fuse_file_alloc(struct fuse_conn *fc)
 {
 	struct fuse_file *ff;
 	ff = kmalloc(sizeof(struct fuse_file), GFP_KERNEL);
@@ -58,6 +58,9 @@ struct fuse_file *fuse_file_alloc(void)
 		} else {
 			INIT_LIST_HEAD(&ff->write_entry);
 			atomic_set(&ff->count, 0);
+			spin_lock(&fc->lock);
+			ff->kh = ++fc->khctr;
+			spin_unlock(&fc->lock);
 		}
 	}
 	return ff;
@@ -108,6 +111,7 @@ void fuse_finish_open(struct inode *inode, struct file *file,
 
 int fuse_open_common(struct inode *inode, struct file *file, int isdir)
 {
+	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_open_out outarg;
 	struct fuse_file *ff;
 	int err;
@@ -120,7 +124,7 @@ int fuse_open_common(struct inode *inode, struct file *file, int isdir)
 	if (err)
 		return err;
 
-	ff = fuse_file_alloc();
+	ff = fuse_file_alloc(fc);
 	if (!ff)
 		return -ENOMEM;
 

fs/fuse/fuse_i.h

@@ -100,6 +100,9 @@ struct fuse_file {
 	/** Request reserved for flush and release */
 	struct fuse_req *reserved_req;
 
+	/** Kernel file handle guaranteed to be unique */
+	u64 kh;
+
 	/** File handle used by userspace */
 	u64 fh;
 
@@ -322,6 +325,9 @@ struct fuse_conn {
 	/** The list of requests under I/O */
 	struct list_head io;
 
+	/** The next unique kernel file handle */
+	u64 khctr;
+
 	/** Number of requests currently in the background */
 	unsigned num_background;
 
@@ -499,7 +505,7 @@ void fuse_read_fill(struct fuse_req *req, struct file *file,
  */
 int fuse_open_common(struct inode *inode, struct file *file, int isdir);
 
-struct fuse_file *fuse_file_alloc(void);
+struct fuse_file *fuse_file_alloc(struct fuse_conn *fc);
 void fuse_file_free(struct fuse_file *ff);
 void fuse_finish_open(struct inode *inode, struct file *file,
 		      struct fuse_file *ff, struct fuse_open_out *outarg);

fs/fuse/inode.c

@@ -485,6 +485,7 @@ static struct fuse_conn *new_conn(struct super_block *sb)
 		fc->bdi.unplug_io_fn = default_unplug_io_fn;
 		/* fuse does it's own writeback accounting */
 		fc->bdi.capabilities = BDI_CAP_NO_ACCT_WB;
+		fc->khctr = 0;
 		fc->dev = sb->s_dev;
 		err = bdi_init(&fc->bdi);
 		if (err)