Commit 4ae404af authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: clean up device cloning 



 - fuse_mutex is not needed for device cloning, because fuse_dev_install()
   uses cmpxcg() to set fud->fc, which prevents races between clone/mount
   or clone/clone.  This makes the logic simpler

 - Drop fc->dev_count.  This is only used to check in release if the device
   is the last clone, but checking list_empty(&fc->devices) is equivalent
   after removing the released device from the list.  Removing the fuse_dev
   before calling fuse_abort_conn() is okay, since the processing and io
   lists are now empty for this device.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent d42eb23b

fs/fuse/dev.c

+15 −20
Original line number Diff line number Diff line
@@ -2547,6 +2547,7 @@ int fuse_dev_release(struct inode *inode, struct file *file) 
		struct fuse_pqueue *fpq = &fud->pq;

		LIST_HEAD(to_end);

		unsigned int i;

		bool last;



		spin_lock(&fpq->lock);

		WARN_ON(!list_empty(&fpq->io));
@@ -2556,14 +2557,16 @@ int fuse_dev_release(struct inode *inode, struct file *file) 


		fuse_dev_end_requests(&to_end);



		spin_lock(&fc->lock);

		list_del(&fud->entry);

		/* Are we the last open device? */

		if (atomic_dec_and_test(&fc->dev_count)) {

		last = list_empty(&fc->devices);

		spin_unlock(&fc->lock);



		if (last) {

			WARN_ON(fc->iq.fasync != NULL);

			fuse_abort_conn(fc);

		}

		spin_lock(&fc->lock);

		list_del(&fud->entry);

		spin_unlock(&fc->lock);

		fuse_conn_put(fc);

	}

	fuse_dev_put(fud);
@@ -2582,23 +2585,10 @@ static int fuse_dev_fasync(int fd, struct file *file, int on) 
	return fasync_helper(fd, file, on, &fud->fc->iq.fasync);

}



static int fuse_device_clone(struct fuse_conn *fc, struct file *new)

{

	struct fuse_dev *new_fud = fuse_file_to_fud(new);



	if (fuse_dev_fc_get(new_fud))

		return -EINVAL;



	fuse_dev_install(new_fud, fc);

	atomic_inc(&fc->dev_count);



	return 0;

}



static long fuse_dev_ioctl_clone(struct file *file, __u32 __user *argp)

{

	int oldfd;

	struct fuse_dev *fud;

	struct fuse_dev *fud, *new_fud;



	if (get_user(oldfd, argp))

		return -EFAULT;
@@ -2618,8 +2608,13 @@ static long fuse_dev_ioctl_clone(struct file *file, __u32 __user *argp) 
	if (IS_ERR(fud))

		return PTR_ERR(fud);



	guard(mutex)(&fuse_mutex);

	return fuse_device_clone(fud->fc, file);

	new_fud = fuse_file_to_fud(file);

	if (fuse_dev_fc_get(new_fud))

		return -EINVAL;



	fuse_dev_install(new_fud, fud->fc);



	return 0;

}



static long fuse_dev_ioctl_backing_open(struct file *file,

fs/fuse/fuse_i.h

+0 −3
Original line number Diff line number Diff line
@@ -650,9 +650,6 @@ struct fuse_conn { 
	/** Refcount */

	refcount_t count;



	/** Number of fuse_dev's */

	atomic_t dev_count;



	/** Current epoch for up-to-date dentries */

	atomic_t epoch;

fs/fuse/inode.c

+0 −1
Original line number Diff line number Diff line
@@ -1001,7 +1001,6 @@ void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm, 
	spin_lock_init(&fc->bg_lock);

	init_rwsem(&fc->killsb);

	refcount_set(&fc->count, 1);

	atomic_set(&fc->dev_count, 1);

	atomic_set(&fc->epoch, 1);

	INIT_WORK(&fc->epoch_work, fuse_epoch_work);

	init_waitqueue_head(&fc->blocked_waitq);