Merge tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse virtio-fs support from Miklos Szeredi:
 "Virtio-fs allows exporting directory trees on the host and mounting
  them in guest(s).

  This isn't actually a new filesystem, but a glue layer between the
  fuse filesystem and a virtio based back-end.

  It's similar in functionality to the existing virtio-9p solution, but
  significantly faster in benchmarks and has better POSIX compliance.
  Further permformance improvements can be achieved by sharing the page
  cache between host and guest, allowing for faster I/O and reduced
  memory use.

  Kata Containers have been including the out-of-tree virtio-fs (with
  the shared page cache patches as well) since version 1.7 as an
  experimental feature. They have been active in development and plan to
  switch from virtio-9p to virtio-fs as their default solution. There
  has been interest from other sources as well.

  The userspace infrastructure is slated to be merged into qemu once the
  kernel part hits mainline.

  This was developed by Vivek Goyal, Dave Gilbert and Stefan Hajnoczi"

* tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  virtio-fs: add virtiofs filesystem
  virtio-fs: add Documentation/filesystems/virtiofs.rst
  fuse: reserve values for mapping protocol

fs/fuse/Kconfig

@@ -27,3 +27,14 @@ config CUSE
 
 	  If you want to develop or use a userspace character device
 	  based on CUSE, answer Y or M.
+
+config VIRTIO_FS
+	tristate "Virtio Filesystem"
+	depends on FUSE_FS
+	select VIRTIO
+	help
+	  The Virtio Filesystem allows guests to mount file systems from the
+          host.
+
+	  If you want to share files between guests or with the host, answer Y
+          or M.

fs/fuse/Makefile

@@ -5,5 +5,6 @@
 
 obj-$(CONFIG_FUSE_FS) += fuse.o
 obj-$(CONFIG_CUSE) += cuse.o
+obj-$(CONFIG_VIRTIO_FS) += virtio_fs.o
 
 fuse-objs := dev.o dir.o file.o inode.o control.o xattr.o acl.o readdir.o

fs/fuse/fuse_i.h

@@ -353,6 +353,10 @@ struct fuse_req {
 	/** Used to wake up the task waiting for completion of request*/
 	wait_queue_head_t waitq;
 
+#if IS_ENABLED(CONFIG_VIRTIO_FS)
+	/** virtio-fs's physically contiguous buffer for in and out args */
+	void *argbuf;
+#endif
 };
 
 struct fuse_iqueue;
@@ -383,6 +387,11 @@ struct fuse_iqueue_ops {
 	 */
 	void (*wake_pending_and_unlock)(struct fuse_iqueue *fiq)
 		__releases(fiq->lock);
+
+	/**
+	 * Clean up when fuse_iqueue is destroyed
+	 */
+	void (*release)(struct fuse_iqueue *fiq);
 };
 
 /** /dev/fuse input queue operations */

fs/fuse/inode.c

@@ -630,6 +630,10 @@ EXPORT_SYMBOL_GPL(fuse_conn_init);
 void fuse_conn_put(struct fuse_conn *fc)
 {
 	if (refcount_dec_and_test(&fc->count)) {
+		struct fuse_iqueue *fiq = &fc->iq;
+
+		if (fiq->ops->release)
+			fiq->ops->release(fiq);
 		put_pid_ns(fc->pid_ns);
 		put_user_ns(fc->user_ns);
 		fc->release(fc);