Merge tag 'fuse-update-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse updates from Miklos Szeredi:
"Scalability and performance improvements, as well as minor bug fixes
and cleanups"

* tag 'fuse-update-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (25 commits)
fuse: cache readdir calls if filesystem opts out of opendir
fuse: support clients that don't implement 'opendir'
fuse: lift bad inode checks into callers
fuse: multiplex cached/direct_io file operations
fuse add copy_file_range to direct io fops
fuse: use iov_iter based generic splice helpers
fuse: Switch to using async direct IO for FOPEN_DIRECT_IO
fuse: use atomic64_t for khctr
fuse: clean up aborted
fuse: Protect ff->reserved_req via corresponding fi->lock
fuse: Protect fi->nlookup with fi->lock
fuse: Introduce fi->lock to protect write related fields
fuse: Convert fc->attr_version into atomic64_t
fuse: Add fuse_inode argument to fuse_prepare_release()
fuse: Verify userspace asks to requeue interrupt that we really sent
fuse: Do some refactoring in fuse_dev_do_write()
fuse: Wake up req->waitq of only if not background
fuse: Optimize request_end() by not taking fiq->waitq.lock
fuse: Kill fasync only if interrupt is queued in queue_interrupt()
fuse: Remove stale comment in end_requests()
...

fs/fuse/control.c

···
 {
 	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
 	if (fc) {
-		fuse_abort_conn(fc, true);
+		if (fc->abort_err)
+			fc->aborted = true;
+		fuse_abort_conn(fc);
 		fuse_conn_put(fc);
 	}
 	return count;

fs/fuse/cuse.c

···
 
 static int cuse_release(struct inode *inode, struct file *file)
 {
+	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_file *ff = file->private_data;
 	struct fuse_conn *fc = ff->fc;
 
-	fuse_sync_release(ff, file->f_flags);
+	fuse_sync_release(fi, ff, file->f_flags);
 	fuse_conn_put(fc);
 
 	return 0;
···
 err_region:
 	unregister_chrdev_region(devt, 1);
 err:
-	fuse_abort_conn(fc, false);
+	fuse_abort_conn(fc);
 	goto out;
 }
 
···
 {
 	struct cuse_conn *cc = dev_get_drvdata(dev);
 
-	fuse_abort_conn(&cc->fc, false);
+	fuse_abort_conn(&cc->fc);
 	return count;
 }
 static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store);

fs/fuse/dev.c

···
 					 struct file *file)
 {
 	struct fuse_req *req = NULL;
+	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
 	struct fuse_file *ff = file->private_data;
 
 	do {
 		wait_event(fc->reserved_req_waitq, ff->reserved_req);
-		spin_lock(&fc->lock);
+		spin_lock(&fi->lock);
 		if (ff->reserved_req) {
 			req = ff->reserved_req;
 			ff->reserved_req = NULL;
 			req->stolen_file = get_file(file);
 		}
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 	} while (!req);
 
 	return req;
···
 static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
 {
 	struct file *file = req->stolen_file;
+	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
 	struct fuse_file *ff = file->private_data;
 
 	WARN_ON(req->max_pages);
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	memset(req, 0, sizeof(*req));
 	fuse_request_init(req, NULL, NULL, 0);
 	BUG_ON(ff->reserved_req);
 	ff->reserved_req = req;
 	wake_up_all(&fc->reserved_req_waitq);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 	fput(file);
 }
 
···
 
 	if (test_and_set_bit(FR_FINISHED, &req->flags))
 		goto put_request;
-
-	spin_lock(&fiq->waitq.lock);
-	list_del_init(&req->intr_entry);
-	spin_unlock(&fiq->waitq.lock);
+	/*
+	 * test_and_set_bit() implies smp_mb() between bit
+	 * changing and below intr_entry check. Pairs with
+	 * smp_mb() from queue_interrupt().
+	 */
+	if (!list_empty(&req->intr_entry)) {
+		spin_lock(&fiq->waitq.lock);
+		list_del_init(&req->intr_entry);
+		spin_unlock(&fiq->waitq.lock);
+	}
 	WARN_ON(test_bit(FR_PENDING, &req->flags));
 	WARN_ON(test_bit(FR_SENT, &req->flags));
 	if (test_bit(FR_BACKGROUND, &req->flags)) {
···
 		fc->active_background--;
 		flush_bg_queue(fc);
 		spin_unlock(&fc->bg_lock);
+	} else {
+		/* Wake up waiter sleeping in request_wait_answer() */
+		wake_up(&req->waitq);
 	}
-	wake_up(&req->waitq);
+
 	if (req->end)
 		req->end(fc, req);
 put_request:
 	fuse_put_request(fc, req);
 }
 
-static void queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
+static int queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
 {
 	spin_lock(&fiq->waitq.lock);
-	if (test_bit(FR_FINISHED, &req->flags)) {
+	/* Check for we've sent request to interrupt this req */
+	if (unlikely(!test_bit(FR_INTERRUPTED, &req->flags))) {
 		spin_unlock(&fiq->waitq.lock);
-		return;
+		return -EINVAL;
 	}
+
 	if (list_empty(&req->intr_entry)) {
 		list_add_tail(&req->intr_entry, &fiq->interrupts);
+		/*
+		 * Pairs with smp_mb() implied by test_and_set_bit()
+		 * from request_end().
+		 */
+		smp_mb();
+		if (test_bit(FR_FINISHED, &req->flags)) {
+			list_del_init(&req->intr_entry);
+			spin_unlock(&fiq->waitq.lock);
+			return 0;
+		}
 		wake_up_locked(&fiq->waitq);
+		kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
 	}
 	spin_unlock(&fiq->waitq.lock);
-	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+	return 0;
 }
 
 static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
···
 		goto err_unlock;
 
 	if (!fiq->connected) {
-		err = (fc->aborted && fc->abort_err) ? -ECONNABORTED : -ENODEV;
+		err = fc->aborted ? -ECONNABORTED : -ENODEV;
 		goto err_unlock;
 	}
 
···
 	spin_lock(&fpq->lock);
 	clear_bit(FR_LOCKED, &req->flags);
 	if (!fpq->connected) {
-		err = (fc->aborted && fc->abort_err) ? -ECONNABORTED : -ENODEV;
+		err = fc->aborted ? -ECONNABORTED : -ENODEV;
 		goto out_end;
 	}
 	if (err) {
···
 	struct fuse_req *req;
 	struct fuse_out_header oh;
 
+	err = -EINVAL;
 	if (nbytes < sizeof(struct fuse_out_header))
-		return -EINVAL;
+		goto out;
 
 	err = fuse_copy_one(cs, &oh, sizeof(oh));
 	if (err)
-		goto err_finish;
+		goto copy_finish;
 
 	err = -EINVAL;
 	if (oh.len != nbytes)
-		goto err_finish;
+		goto copy_finish;
 
 	/*
 	 * Zero oh.unique indicates unsolicited notification message
···
 	 */
 	if (!oh.unique) {
 		err = fuse_notify(fc, oh.error, nbytes - sizeof(oh), cs);
-		return err ? err : nbytes;
+		goto out;
 	}
 
 	err = -EINVAL;
 	if (oh.error <= -1000 || oh.error > 0)
-		goto err_finish;
+		goto copy_finish;
 
 	spin_lock(&fpq->lock);
-	err = -ENOENT;
-	if (!fpq->connected)
-		goto err_unlock_pq;
+	req = NULL;
+	if (fpq->connected)
+		req = request_find(fpq, oh.unique & ~FUSE_INT_REQ_BIT);
 
-	req = request_find(fpq, oh.unique & ~FUSE_INT_REQ_BIT);
-	if (!req)
-		goto err_unlock_pq;
+	err = -ENOENT;
+	if (!req) {
+		spin_unlock(&fpq->lock);
+		goto copy_finish;
+	}
 
 	/* Is it an interrupt reply ID? */
 	if (oh.unique & FUSE_INT_REQ_BIT) {
 		__fuse_get_request(req);
 		spin_unlock(&fpq->lock);
 
-		err = -EINVAL;
-		if (nbytes != sizeof(struct fuse_out_header)) {
-			fuse_put_request(fc, req);
-			goto err_finish;
-		}
-
-		if (oh.error == -ENOSYS)
+		err = 0;
+		if (nbytes != sizeof(struct fuse_out_header))
+			err = -EINVAL;
+		else if (oh.error == -ENOSYS)
 			fc->no_interrupt = 1;
 		else if (oh.error == -EAGAIN)
-			queue_interrupt(&fc->iq, req);
+			err = queue_interrupt(&fc->iq, req);
+
 		fuse_put_request(fc, req);
 
-		fuse_copy_finish(cs);
-		return nbytes;
+		goto copy_finish;
 	}
 
 	clear_bit(FR_SENT, &req->flags);
···
 	spin_unlock(&fpq->lock);
 
 	request_end(fc, req);
-
+out:
 	return err ? err : nbytes;
 
- err_unlock_pq:
-	spin_unlock(&fpq->lock);
- err_finish:
+copy_finish:
 	fuse_copy_finish(cs);
-	return err;
+	goto out;
 }
 
 static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
···
 	return mask;
 }
 
-/*
- * Abort all requests on the given list (pending or processing)
- *
- * This function releases and reacquires fc->lock
- */
+/* Abort all requests on the given list (pending or processing) */
 static void end_requests(struct fuse_conn *fc, struct list_head *head)
 {
 	while (!list_empty(head)) {
···
  * is OK, the request will in that case be removed from the list before we touch
  * it.
  */
-void fuse_abort_conn(struct fuse_conn *fc, bool is_abort)
+void fuse_abort_conn(struct fuse_conn *fc)
 {
 	struct fuse_iqueue *fiq = &fc->iq;
 
···
 		fc->connected = 0;
 		spin_unlock(&fc->bg_lock);
 
-		fc->aborted = is_abort;
 		fuse_set_initialized(fc);
 		list_for_each_entry(fud, &fc->devices, entry) {
 			struct fuse_pqueue *fpq = &fud->pq;
···
 		/* Are we the last open device? */
 		if (atomic_dec_and_test(&fc->dev_count)) {
 			WARN_ON(fc->iq.fasync != NULL);
-			fuse_abort_conn(fc, false);
+			fuse_abort_conn(fc);
 		}
 		fuse_dev_free(fud);
 	}

fs/fuse/dir.c

···
 	args->out.args[0].value = outarg;
 }
 
-u64 fuse_get_attr_version(struct fuse_conn *fc)
-{
-	u64 curr_version;
-
-	/*
-	 * The spin lock isn't actually needed on 64bit archs, but we
-	 * don't yet care too much about such optimizations.
-	 */
-	spin_lock(&fc->lock);
-	curr_version = fc->attr_version;
-	spin_unlock(&fc->lock);
-
-	return curr_version;
-}
-
 /*
  * Check whether the dentry is still valid
  *
···
 				fuse_queue_forget(fc, forget, outarg.nodeid, 1);
 				goto invalid;
 			}
-			spin_lock(&fc->lock);
+			spin_lock(&fi->lock);
 			fi->nlookup++;
-			spin_unlock(&fc->lock);
+			spin_unlock(&fi->lock);
 		}
 		kfree(forget);
 		if (ret == -ENOMEM)
···
 	struct fuse_create_in inarg;
 	struct fuse_open_out outopen;
 	struct fuse_entry_out outentry;
+	struct fuse_inode *fi;
 	struct fuse_file *ff;
 
 	/* Userspace expects S_IFREG in create mode */
···
 			  &outentry.attr, entry_attr_timeout(&outentry), 0);
 	if (!inode) {
 		flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
-		fuse_sync_release(ff, flags);
+		fuse_sync_release(NULL, ff, flags);
 		fuse_queue_forget(fc, forget, outentry.nodeid, 1);
 		err = -ENOMEM;
 		goto out_err;
···
 	fuse_dir_changed(dir);
 	err = finish_open(file, entry, generic_file_open);
 	if (err) {
-		fuse_sync_release(ff, flags);
+		fi = get_fuse_inode(inode);
+		fuse_sync_release(fi, ff, flags);
 	} else {
 		file->private_data = ff;
 		fuse_finish_open(inode, file);
···
 		struct inode *inode = d_inode(entry);
 		struct fuse_inode *fi = get_fuse_inode(inode);
 
-		spin_lock(&fc->lock);
-		fi->attr_version = ++fc->attr_version;
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
 		/*
 		 * If i_nlink == 0 then unlink doesn't make sense, yet this can
 		 * happen if userspace filesystem is careless.  It would be
···
 		 */
 		if (inode->i_nlink > 0)
 			drop_nlink(inode);
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 		fuse_invalidate_attr(inode);
 		fuse_dir_changed(dir);
 		fuse_invalidate_entry_cache(entry);
···
 	if (!err) {
 		struct fuse_inode *fi = get_fuse_inode(inode);
 
-		spin_lock(&fc->lock);
-		fi->attr_version = ++fc->attr_version;
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
 		inc_nlink(inode);
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 		fuse_invalidate_attr(inode);
 		fuse_update_ctime(inode);
 	} else if (err == -EINTR) {
···
  */
 void fuse_set_nowrite(struct inode *inode)
 {
-	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
 
 	BUG_ON(!inode_is_locked(inode));
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	BUG_ON(fi->writectr < 0);
 	fi->writectr += FUSE_NOWRITE;
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 	wait_event(fi->page_waitq, fi->writectr == FUSE_NOWRITE);
 }
 
···
 
 void fuse_release_nowrite(struct inode *inode)
 {
-	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	__fuse_release_nowrite(inode);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 }
 
 static void fuse_setattr_fill(struct fuse_conn *fc, struct fuse_args *args,
···
 		goto error;
 	}
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	/* the kernel maintains i_mtime locally */
 	if (trust_local_cmtime) {
 		if (attr->ia_valid & ATTR_MTIME)
···
 		i_size_write(inode, outarg.attr.size);
 
 	if (is_truncate) {
-		/* NOTE: this may release/reacquire fc->lock */
+		/* NOTE: this may release/reacquire fi->lock */
 		__fuse_release_nowrite(inode);
 	}
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 	/*
 	 * Only call invalidate_inode_pages2() after removing

fs/fuse/file.c

···
 #include <linux/falloc.h>
 #include <linux/uio.h>
 
-static const struct file_operations fuse_direct_io_file_operations;
-
 static int fuse_send_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
 			  int opcode, struct fuse_open_out *outargp)
 {
···
 	RB_CLEAR_NODE(&ff->polled_node);
 	init_waitqueue_head(&ff->poll_wait);
 
-	spin_lock(&fc->lock);
-	ff->kh = ++fc->khctr;
-	spin_unlock(&fc->lock);
+	ff->kh = atomic64_inc_return(&fc->khctr);
 
 	return ff;
 }
···
 	if (refcount_dec_and_test(&ff->count)) {
 		struct fuse_req *req = ff->reserved_req;
 
-		if (ff->fc->no_open && !isdir) {
+		if (isdir ? ff->fc->no_opendir : ff->fc->no_open) {
 			/*
 			 * Drop the release request when client does not
 			 * implement 'open'
···
 		return -ENOMEM;
 
 	ff->fh = 0;
-	ff->open_flags = FOPEN_KEEP_CACHE; /* Default for no-open */
-	if (!fc->no_open || isdir) {
+	/* Default for no-open */
+	ff->open_flags = FOPEN_KEEP_CACHE | (isdir ? FOPEN_CACHE_DIR : 0);
+	if (isdir ? !fc->no_opendir : !fc->no_open) {
 		struct fuse_open_out outarg;
 		int err;
 
···
 			ff->fh = outarg.fh;
 			ff->open_flags = outarg.open_flags;
 
-		} else if (err != -ENOSYS || isdir) {
+		} else if (err != -ENOSYS) {
 			fuse_file_free(ff);
 			return err;
 		} else {
-			fc->no_open = 1;
+			if (isdir)
+				fc->no_opendir = 1;
+			else
+				fc->no_open = 1;
 		}
 	}
 
···
 static void fuse_link_write_file(struct file *file)
 {
 	struct inode *inode = file_inode(file);
-	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_file *ff = file->private_data;
 	/*
 	 * file may be written through mmap, so chain it onto the
 	 * inodes's write_file list
 	 */
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	if (list_empty(&ff->write_entry))
 		list_add(&ff->write_entry, &fi->write_files);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 }
 
 void fuse_finish_open(struct inode *inode, struct file *file)
···
 	struct fuse_file *ff = file->private_data;
 	struct fuse_conn *fc = get_fuse_conn(inode);
 
-	if (ff->open_flags & FOPEN_DIRECT_IO)
-		file->f_op = &fuse_direct_io_file_operations;
 	if (!(ff->open_flags & FOPEN_KEEP_CACHE))
 		invalidate_inode_pages2(inode->i_mapping);
 	if (ff->open_flags & FOPEN_NONSEEKABLE)
···
 	if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
 		struct fuse_inode *fi = get_fuse_inode(inode);
 
-		spin_lock(&fc->lock);
-		fi->attr_version = ++fc->attr_version;
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
 		i_size_write(inode, 0);
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 		fuse_invalidate_attr(inode);
 		if (fc->writeback_cache)
 			file_update_time(file);
···
 	return err;
 }
 
-static void fuse_prepare_release(struct fuse_file *ff, int flags, int opcode)
+static void fuse_prepare_release(struct fuse_inode *fi, struct fuse_file *ff,
+				 int flags, int opcode)
 {
 	struct fuse_conn *fc = ff->fc;
 	struct fuse_req *req = ff->reserved_req;
 	struct fuse_release_in *inarg = &req->misc.release.in;
 
+	/* Inode is NULL on error path of fuse_create_open() */
+	if (likely(fi)) {
+		spin_lock(&fi->lock);
+		list_del(&ff->write_entry);
+		spin_unlock(&fi->lock);
+	}
 	spin_lock(&fc->lock);
-	list_del(&ff->write_entry);
 	if (!RB_EMPTY_NODE(&ff->polled_node))
 		rb_erase(&ff->polled_node, &fc->polled_files);
 	spin_unlock(&fc->lock);
···
 
 void fuse_release_common(struct file *file, bool isdir)
 {
+	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
 	struct fuse_file *ff = file->private_data;
 	struct fuse_req *req = ff->reserved_req;
 	int opcode = isdir ? FUSE_RELEASEDIR : FUSE_RELEASE;
 
-	fuse_prepare_release(ff, file->f_flags, opcode);
+	fuse_prepare_release(fi, ff, file->f_flags, opcode);
 
 	if (ff->flock) {
 		struct fuse_release_in *inarg = &req->misc.release.in;
···
 	return 0;
 }
 
-void fuse_sync_release(struct fuse_file *ff, int flags)
+void fuse_sync_release(struct fuse_inode *fi, struct fuse_file *ff, int flags)
 {
 	WARN_ON(refcount_read(&ff->count) > 1);
-	fuse_prepare_release(ff, flags, FUSE_RELEASE);
+	fuse_prepare_release(fi, ff, flags, FUSE_RELEASE);
 	/*
 	 * iput(NULL) is a no-op and since the refcount is 1 and everything's
 	 * synchronous, we are fine with not doing igrab() here"
···
 	return (u64) v0 + ((u64) v1 << 32);
 }
 
+static struct fuse_req *fuse_find_writeback(struct fuse_inode *fi,
+					    pgoff_t idx_from, pgoff_t idx_to)
+{
+	struct fuse_req *req;
+
+	list_for_each_entry(req, &fi->writepages, writepages_entry) {
+		pgoff_t curr_index;
+
+		WARN_ON(get_fuse_inode(req->inode) != fi);
+		curr_index = req->misc.write.in.offset >> PAGE_SHIFT;
+		if (idx_from < curr_index + req->num_pages &&
+		    curr_index <= idx_to) {
+			return req;
+		}
+	}
+	return NULL;
+}
+
 /*
  * Check if any page in a range is under writeback
  *
···
 static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from,
 				   pgoff_t idx_to)
 {
-	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
-	struct fuse_req *req;
-	bool found = false;
+	bool found;
 
-	spin_lock(&fc->lock);
-	list_for_each_entry(req, &fi->writepages, writepages_entry) {
-		pgoff_t curr_index;
-
-		BUG_ON(req->inode != inode);
-		curr_index = req->misc.write.in.offset >> PAGE_SHIFT;
-		if (idx_from < curr_index + req->num_pages &&
-		    curr_index <= idx_to) {
-			found = true;
-			break;
-		}
-	}
-	spin_unlock(&fc->lock);
+	spin_lock(&fi->lock);
+	found = fuse_find_writeback(fi, idx_from, idx_to);
+	spin_unlock(&fi->lock);
 
 	return found;
 }
···
 			struct fuse_conn *fc = get_fuse_conn(inode);
 			struct fuse_inode *fi = get_fuse_inode(inode);
 
-			spin_lock(&fc->lock);
-			fi->attr_version = ++fc->attr_version;
-			spin_unlock(&fc->lock);
+			spin_lock(&fi->lock);
+			fi->attr_version = atomic64_inc_return(&fc->attr_version);
+			spin_unlock(&fi->lock);
 		}
 
 		io->iocb->ki_complete(io->iocb, res, 0);
···
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	if (attr_ver == fi->attr_version && size < inode->i_size &&
 	    !test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
-		fi->attr_version = ++fc->attr_version;
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
 		i_size_write(inode, size);
 	}
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 }
 
 static void fuse_short_read(struct fuse_req *req, struct inode *inode,
···
 	return err;
 }
 
-static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
 	struct inode *inode = iocb->ki_filp->f_mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
···
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	bool ret = false;
 
-	spin_lock(&fc->lock);
-	fi->attr_version = ++fc->attr_version;
+	spin_lock(&fi->lock);
+	fi->attr_version = atomic64_inc_return(&fc->attr_version);
 	if (pos > inode->i_size) {
 		i_size_write(inode, pos);
 		ret = true;
 	}
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 	return ret;
 }
···
 	int err = 0;
 	ssize_t res = 0;
 
-	if (is_bad_inode(inode))
-		return -EIO;
-
 	if (inode->i_size < pos + iov_iter_count(ii))
 		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
 
···
 	return res > 0 ? res : err;
 }
 
-static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
 	struct address_space *mapping = file->f_mapping;
···
 	ssize_t res;
 	struct inode *inode = file_inode(io->iocb->ki_filp);
 
-	if (is_bad_inode(inode))
-		return -EIO;
-
 	res = fuse_direct_io(io, iter, ppos, 0);
 
 	fuse_invalidate_atime(inode);
···
 	return res;
 }
 
+static ssize_t fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
+
 static ssize_t fuse_direct_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
-	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
-	return __fuse_direct_read(&io, to, &iocb->ki_pos);
+	ssize_t res;
+
+	if (!is_sync_kiocb(iocb) && iocb->ki_flags & IOCB_DIRECT) {
+		res = fuse_direct_IO(iocb, to);
+	} else {
+		struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
+
+		res = __fuse_direct_read(&io, to, &iocb->ki_pos);
+	}
+
+	return res;
 }
 
 static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
···
 	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
 	ssize_t res;
 
-	if (is_bad_inode(inode))
-		return -EIO;
-
 	/* Don't allow parallel writes to the same file */
 	inode_lock(inode);
 	res = generic_write_checks(iocb, from);
-	if (res > 0)
-		res = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE);
+	if (res > 0) {
+		if (!is_sync_kiocb(iocb) && iocb->ki_flags & IOCB_DIRECT) {
+			res = fuse_direct_IO(iocb, from);
+		} else {
+			res = fuse_direct_io(&io, from, &iocb->ki_pos,
+					     FUSE_DIO_WRITE);
+		}
+	}
 	fuse_invalidate_attr(inode);
 	if (res > 0)
 		fuse_write_update_size(inode, iocb->ki_pos);
 	inode_unlock(inode);
 
 	return res;
+}
+
+static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+
+	if (is_bad_inode(file_inode(file)))
+		return -EIO;
+
+	if (!(ff->open_flags & FOPEN_DIRECT_IO))
+		return fuse_cache_read_iter(iocb, to);
+	else
+		return fuse_direct_read_iter(iocb, to);
+}
+
+static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+
+	if (is_bad_inode(file_inode(file)))
+		return -EIO;
+
+	if (!(ff->open_flags & FOPEN_DIRECT_IO))
+		return fuse_cache_write_iter(iocb, from);
+	else
+		return fuse_direct_write_iter(iocb, from);
 }
 
 static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)
···
 	wake_up(&fi->page_waitq);
 }
 
-/* Called under fc->lock, may release and reacquire it */
+/* Called under fi->lock, may release and reacquire it */
 static void fuse_send_writepage(struct fuse_conn *fc, struct fuse_req *req,
 				loff_t size)
-__releases(fc->lock)
-__acquires(fc->lock)
+__releases(fi->lock)
+__acquires(fi->lock)
 {
+	struct fuse_req *aux, *next;
 	struct fuse_inode *fi = get_fuse_inode(req->inode);
 	struct fuse_write_in *inarg = &req->misc.write.in;
 	__u64 data_size = req->num_pages * PAGE_SIZE;
 	bool queued;
-
-	if (!fc->connected)
-		goto out_free;
 
 	if (inarg->offset + data_size <= size) {
 		inarg->size = data_size;
···
 	}
 
 	req->in.args[1].size = inarg->size;
-	fi->writectr++;
 	queued = fuse_request_queue_background(fc, req);
-	WARN_ON(!queued);
+	/* Fails on broken connection only */
+	if (unlikely(!queued))
+		goto out_free;
+
+	fi->writectr++;
 	return;
 
  out_free:
 	fuse_writepage_finish(fc, req);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
+
+	/* After fuse_writepage_finish() aux request list is private */
+	for (aux = req->misc.write.next; aux; aux = next) {
+		next = aux->misc.write.next;
+		aux->misc.write.next = NULL;
+		fuse_writepage_free(fc, aux);
+		fuse_put_request(fc, aux);
+	}
+
 	fuse_writepage_free(fc, req);
 	fuse_put_request(fc, req);
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 }
 
 /*
  * If fi->writectr is positive (no truncate or fsync going on) send
  * all queued writepage requests.
  *
- * Called with fc->lock
+ * Called with fi->lock
  */
 void fuse_flush_writepages(struct inode *inode)
-__releases(fc->lock)
-__acquires(fc->lock)
+__releases(fi->lock)
+__acquires(fi->lock)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
···
 	struct fuse_inode *fi = get_fuse_inode(inode);
 
 	mapping_set_error(inode->i_mapping, req->out.h.error);
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	while (req->misc.write.next) {
 		struct fuse_conn *fc = get_fuse_conn(inode);
 		struct fuse_write_in *inarg = &req->misc.write.in;
···
 	}
 	fi->writectr--;
 	fuse_writepage_finish(fc, req);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 	fuse_writepage_free(fc, req);
 }
 
···
 {
 	struct fuse_file *ff = NULL;
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	if (!list_empty(&fi->write_files)) {
 		ff = list_entry(fi->write_files.next, struct fuse_file,
 				write_entry);
 		fuse_file_get(ff);
 	}
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 	return ff;
 }
···
 	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
 	inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP);
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	list_add(&req->writepages_entry, &fi->writepages);
 	list_add_tail(&req->list, &fi->queued_writes);
 	fuse_flush_writepages(inode);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 	end_page_writeback(page);
 
···
 {
 	struct fuse_req *req = data->req;
 	struct inode *inode = data->inode;
-	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	int num_pages = req->num_pages;
 	int i;
 
 	req->ff = fuse_file_get(data->ff);
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	list_add_tail(&req->list, &fi->queued_writes);
 	fuse_flush_writepages(inode);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 	for (i = 0; i < num_pages; i++)
 		end_page_writeback(data->orig_pages[i]);
 }
 
+/*
+ * First recheck under fi->lock if the offending offset is still under
+ * writeback.  If yes, then iterate auxiliary write requests, to see if there's
+ * one already added for a page at this offset.  If there's none, then insert
+ * this new request onto the auxiliary list, otherwise reuse the existing one by
+ * copying the new page contents over to the old temporary page.
+ */
 static bool fuse_writepage_in_flight(struct fuse_req *new_req,
 				     struct page *page)
 {
···
 	struct fuse_inode *fi = get_fuse_inode(new_req->inode);
 	struct fuse_req *tmp;
 	struct fuse_req *old_req;
-	bool found = false;
-	pgoff_t curr_index;
 
-	BUG_ON(new_req->num_pages != 0);
+	WARN_ON(new_req->num_pages != 0);
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	list_del(&new_req->writepages_entry);
-	list_for_each_entry(old_req, &fi->writepages, writepages_entry) {
-		BUG_ON(old_req->inode != new_req->inode);
-		curr_index = old_req->misc.write.in.offset >> PAGE_SHIFT;
-		if (curr_index <= page->index &&
-		    page->index < curr_index + old_req->num_pages) {
-			found = true;
-			break;
-		}
-	}
-	if (!found) {
+	old_req = fuse_find_writeback(fi, page->index, page->index);
+	if (!old_req) {
 		list_add(&new_req->writepages_entry, &fi->writepages);
-		goto out_unlock;
+		spin_unlock(&fi->lock);
+		return false;
 	}
 
 	new_req->num_pages = 1;
-	for (tmp = old_req; tmp != NULL; tmp = tmp->misc.write.next) {
-		BUG_ON(tmp->inode != new_req->inode);
+	for (tmp = old_req->misc.write.next; tmp; tmp = tmp->misc.write.next) {
+		pgoff_t curr_index;
+
+		WARN_ON(tmp->inode != new_req->inode);
 		curr_index = tmp->misc.write.in.offset >> PAGE_SHIFT;
-		if (tmp->num_pages == 1 &&
-		    curr_index == page->index) {
-			old_req = tmp;
+		if (curr_index == page->index) {
+			WARN_ON(tmp->num_pages != 1);
+			WARN_ON(!test_bit(FR_PENDING, &tmp->flags));
+			swap(tmp->pages[0], new_req->pages[0]);
+			break;
 		}
 	}
 
-	if (old_req->num_pages == 1 && test_bit(FR_PENDING, &old_req->flags)) {
-		struct backing_dev_info *bdi = inode_to_bdi(page->mapping->host);
+	if (!tmp) {
+		new_req->misc.write.next = old_req->misc.write.next;
+		old_req->misc.write.next = new_req;
+	}
 
-		copy_highpage(old_req->pages[0], page);
-		spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
+
+	if (tmp) {
+		struct backing_dev_info *bdi = inode_to_bdi(new_req->inode);
 
 		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
 		dec_node_page_state(new_req->pages[0], NR_WRITEBACK_TEMP);
 		wb_writeout_inc(&bdi->wb);
 		fuse_writepage_free(fc, new_req);
 		fuse_request_free(new_req);
-		goto out;
-	} else {
-		new_req->misc.write.next = old_req->misc.write.next;
-		old_req->misc.write.next = new_req;
 	}
-out_unlock:
-	spin_unlock(&fc->lock);
-out:
-	return found;
+
+	return true;
 }
 
 static int fuse_writepages_fill(struct page *page,
···
 	struct fuse_fill_wb_data *data = _data;
 	struct fuse_req *req = data->req;
 	struct inode *inode = data->inode;
+	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct page *tmp_page;
 	bool is_writeback;
···
 		req->end = fuse_writepage_end;
 		req->inode = inode;
 
-		spin_lock(&fc->lock);
+		spin_lock(&fi->lock);
 		list_add(&req->writepages_entry, &fi->writepages);
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 
 		data->req = req;
 	}
···
 	data->orig_pages[req->num_pages] = page;
 
 	/*
-	 * Protected by fc->lock against concurrent access by
+	 * Protected by fi->lock against concurrent access by
 	 * fuse_page_is_writeback().
 	 */
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	req->num_pages++;
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 out_unlock:
 	unlock_page(page);
···
 
 static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
+	struct fuse_file *ff = file->private_data;
+
+	if (ff->open_flags & FOPEN_DIRECT_IO) {
+		/* Can't provide the coherency needed for MAP_SHARED */
+		if (vma->vm_flags & VM_MAYSHARE)
+			return -ENODEV;
+
+		invalidate_inode_pages2(file->f_mapping);
+
+		return generic_file_mmap(file, vma);
+	}
+
 	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
 		fuse_link_write_file(file);
 
 	file_accessed(file);
 	vma->vm_ops = &fuse_file_vm_ops;
 	return 0;
-}
-
-static int fuse_direct_mmap(struct file *file, struct vm_area_struct *vma)
-{
-	/* Can't provide the coherency needed for MAP_SHARED */
-	if (vma->vm_flags & VM_MAYSHARE)
-		return -ENODEV;
-
-	invalidate_inode_pages2(file->f_mapping);
-
-	return generic_file_mmap(file, vma);
 }
 
 static int convert_fuse_file_lock(struct fuse_conn *fc,
···
 	.lock		= fuse_file_lock,
 	.flock		= fuse_file_flock,
 	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_write,
 	.unlocked_ioctl	= fuse_file_ioctl,
 	.compat_ioctl	= fuse_file_compat_ioctl,
 	.poll		= fuse_file_poll,
 	.fallocate	= fuse_file_fallocate,
 	.copy_file_range = fuse_copy_file_range,
-};
-
-static const struct file_operations fuse_direct_io_file_operations = {
-	.llseek		= fuse_file_llseek,
-	.read_iter	= fuse_direct_read_iter,
-	.write_iter	= fuse_direct_write_iter,
-	.mmap		= fuse_direct_mmap,
-	.open		= fuse_open,
-	.flush		= fuse_flush,
-	.release	= fuse_release,
-	.fsync		= fuse_fsync,
-	.lock		= fuse_file_lock,
-	.flock		= fuse_file_flock,
-	.unlocked_ioctl	= fuse_file_ioctl,
-	.compat_ioctl	= fuse_file_compat_ioctl,
-	.poll		= fuse_file_poll,
-	.fallocate	= fuse_file_fallocate,
-	/* no splice_read */
 };
 
 static const struct address_space_operations fuse_file_aops  = {

fs/fuse/fuse_i.h

···
 	union {
 		/* Write related fields (regular file only) */
 		struct {
-			/* Files usable in writepage.  Protected by fc->lock */
+			/* Files usable in writepage.  Protected by fi->lock */
 			struct list_head write_files;
 
 			/* Writepages pending on truncate or fsync */
···
 
 	/** Lock for serializing lookup and readdir for back compatibility*/
 	struct mutex mutex;
+
+	/** Lock to protect write related fields */
+	spinlock_t lock;
 };
 
 /** FUSE inode state bits */
···
 	/** Fuse connection for this file */
 	struct fuse_conn *fc;
 
-	/** Request reserved for flush and release */
+	/*
+	 * Request reserved for flush and release.
+	 * Modified under relative fuse_inode::lock.
+	 */
 	struct fuse_req *reserved_req;
 
 	/** Kernel file handle guaranteed to be unique */
···
 	struct fuse_iqueue iq;
 
 	/** The next unique kernel file handle */
-	u64 khctr;
+	atomic64_t khctr;
 
 	/** rbtree of fuse_files waiting for poll events indexed by ph */
 	struct rb_root polled_files;
···
 
 	/** Is open/release not implemented by fs? */
 	unsigned no_open:1;
+
+	/** Is opendir/releasedir not implemented by fs? */
+	unsigned no_opendir:1;
 
 	/** Is fsync not implemented by fs? */
 	unsigned no_fsync:1;
···
 	struct fuse_req *destroy_req;
 
 	/** Version counter for attribute changes */
-	u64 attr_version;
+	atomic64_t attr_version;
 
 	/** Called on final put */
 	void (*release)(struct fuse_conn *);
···
 static inline int invalid_nodeid(u64 nodeid)
 {
 	return !nodeid || nodeid == FUSE_ROOT_ID;
+}
+
+static inline u64 fuse_get_attr_version(struct fuse_conn *fc)
+{
+	return atomic64_read(&fc->attr_version);
 }
 
 /** Device operations */
···
 void fuse_file_free(struct fuse_file *ff);
 void fuse_finish_open(struct inode *inode, struct file *file);
 
-void fuse_sync_release(struct fuse_file *ff, int flags);
+void fuse_sync_release(struct fuse_inode *fi, struct fuse_file *ff, int flags);
 
 /**
  * Send RELEASE or RELEASEDIR request
···
 bool fuse_request_queue_background(struct fuse_conn *fc, struct fuse_req *req);
 
 /* Abort all requests */
-void fuse_abort_conn(struct fuse_conn *fc, bool is_abort);
+void fuse_abort_conn(struct fuse_conn *fc);
 void fuse_wait_aborted(struct fuse_conn *fc);
 
 /**
···
 
 void fuse_set_nowrite(struct inode *inode);
 void fuse_release_nowrite(struct inode *inode);
-
-u64 fuse_get_attr_version(struct fuse_conn *fc);
 
 /**
  * File-system tells the kernel to invalidate cache for the given node id.

fs/fuse/inode.c

···
 	fi->orig_ino = 0;
 	fi->state = 0;
 	mutex_init(&fi->mutex);
+	spin_lock_init(&fi->lock);
 	fi->forget = fuse_alloc_forget();
 	if (!fi->forget) {
 		kmem_cache_free(fuse_inode_cachep, inode);
···
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
 
-	fi->attr_version = ++fc->attr_version;
+	lockdep_assert_held(&fi->lock);
+
+	fi->attr_version = atomic64_inc_return(&fc->attr_version);
 	fi->i_time = attr_valid;
 	WRITE_ONCE(fi->inval_mask, 0);
 
···
 	loff_t oldsize;
 	struct timespec64 old_mtime;
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	if ((attr_version != 0 && fi->attr_version > attr_version) ||
 	    test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 		return;
 	}
 
···
 	 */
 	if (!is_wb || !S_ISREG(inode->i_mode))
 		i_size_write(inode, attr->size);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 	if (!is_wb && S_ISREG(inode->i_mode)) {
 		bool inval = false;
···
 	}
 
 	fi = get_fuse_inode(inode);
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	fi->nlookup++;
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 	fuse_change_attributes(inode, attr, attr_valid, attr_version);
 
 	return inode;
···
 
 static void fuse_umount_begin(struct super_block *sb)
 {
-	fuse_abort_conn(get_fuse_conn_super(sb), false);
+	fuse_abort_conn(get_fuse_conn_super(sb));
 }
 
 static void fuse_send_destroy(struct fuse_conn *fc)
···
 	atomic_set(&fc->num_waiting, 0);
 	fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
 	fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;
-	fc->khctr = 0;
+	atomic64_set(&fc->khctr, 0);
 	fc->polled_files = RB_ROOT;
 	fc->blocked = 0;
 	fc->initialized = 0;
 	fc->connected = 1;
-	fc->attr_version = 1;
+	atomic64_set(&fc->attr_version, 1);
 	get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
 	fc->pid_ns = get_pid_ns(task_active_pid_ns(current));
 	fc->user_ns = get_user_ns(user_ns);
···
 		FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO |
 		FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
 		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
-		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS;
+		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
+		FUSE_NO_OPENDIR_SUPPORT;
 	req->in.h.opcode = FUSE_INIT;
 	req->in.numargs = 1;
 	req->in.args[0].size = sizeof(*arg);
···
 	if (fc) {
 		fuse_send_destroy(fc);
 
-		fuse_abort_conn(fc, false);
+		fuse_abort_conn(fc);
 		fuse_wait_aborted(fc);
 
 		down_write(&fc->killsb);

fs/fuse/readdir.c

···
 		}
 
 		fi = get_fuse_inode(inode);
-		spin_lock(&fc->lock);
+		spin_lock(&fi->lock);
 		fi->nlookup++;
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 
 		forget_all_cached_acls(inode);
 		fuse_change_attributes(inode, &o->attr,

include/uapi/linux/fuse.h

···
  *  - add FOPEN_CACHE_DIR
  *  - add FUSE_MAX_PAGES, add max_pages to init_out
  *  - add FUSE_CACHE_SYMLINKS
+ *
+ *  7.29
+ *  - add FUSE_NO_OPENDIR_SUPPORT flag
  */
 
 #ifndef _LINUX_FUSE_H
···
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 28
+#define FUSE_KERNEL_MINOR_VERSION 29
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
···
  * FUSE_ABORT_ERROR: reading the device after abort returns ECONNABORTED
  * FUSE_MAX_PAGES: init_out.max_pages contains the max number of req pages
  * FUSE_CACHE_SYMLINKS: cache READLINK responses
+ * FUSE_NO_OPENDIR_SUPPORT: kernel supports zero-message opendir
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
···
 #define FUSE_ABORT_ERROR	(1 << 21)
 #define FUSE_MAX_PAGES		(1 << 22)
 #define FUSE_CACHE_SYMLINKS	(1 << 23)
+#define FUSE_NO_OPENDIR_SUPPORT (1 << 24)
 
 /**
  * CUSE INIT request/reply flags