Merge tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull fd prepare updates from Christian Brauner:
 "This adds the FD_ADD() and FD_PREPARE() primitive. They simplify the
  common pattern of get_unused_fd_flags() + create file + fd_install()
  that is used extensively throughout the kernel and currently requires
  cumbersome cleanup paths.

  FD_ADD() - For simple cases where a file is installed immediately:

      fd = FD_ADD(O_CLOEXEC, vfio_device_open_file(device));
      if (fd < 0)
          vfio_device_put_registration(device);
      return fd;

  FD_PREPARE() - For cases requiring access to the fd or file, or
  additional work before publishing:

      FD_PREPARE(fdf, O_CLOEXEC, sync_file->file);
      if (fdf.err) {
          fput(sync_file->file);
          return fdf.err;
      }

      data.fence = fd_prepare_fd(fdf);
      if (copy_to_user((void __user *)arg, &data, sizeof(data)))
          return -EFAULT;

      return fd_publish(fdf);

  The primitives are centered around struct fd_prepare. FD_PREPARE()
  encapsulates all allocation and cleanup logic and must be followed by
  a call to fd_publish() which associates the fd with the file and
  installs it into the caller's fdtable. If fd_publish() isn't called,
  both are deallocated automatically. FD_ADD() is a shorthand that does
  fd_publish() immediately and never exposes the struct to the caller.

  I've implemented this in a way that it's compatible with the cleanup
  infrastructure while also being usable separately. IOW, it's centered
  around struct fd_prepare which is aliased to class_fd_prepare_t and so
  we can make use of all the basica guard infrastructure"

* tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (42 commits)
  io_uring: convert io_create_mock_file() to FD_PREPARE()
  file: convert replace_fd() to FD_PREPARE()
  vfio: convert vfio_group_ioctl_get_device_fd() to FD_ADD()
  tty: convert ptm_open_peer() to FD_ADD()
  ntsync: convert ntsync_obj_get_fd() to FD_PREPARE()
  media: convert media_request_alloc() to FD_PREPARE()
  hv: convert mshv_ioctl_create_partition() to FD_ADD()
  gpio: convert linehandle_create() to FD_PREPARE()
  pseries: port papr_rtas_setup_file_interface() to FD_ADD()
  pseries: convert papr_platform_dump_create_handle() to FD_ADD()
  spufs: convert spufs_gang_open() to FD_PREPARE()
  papr-hvpipe: convert papr_hvpipe_dev_create_handle() to FD_PREPARE()
  spufs: convert spufs_context_open() to FD_PREPARE()
  net/socket: convert __sys_accept4_file() to FD_ADD()
  net/socket: convert sock_map_fd() to FD_ADD()
  net/kcm: convert kcm_ioctl() to FD_PREPARE()
  net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE()
  secretmem: convert memfd_secret() to FD_ADD()
  memfd: convert memfd_create() to FD_ADD()
  bpf: convert bpf_token_create() to FD_PREPARE()
  ...

1 files changed, 15 insertions, 28 deletions

diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index 45d3735b2708..3ffac8f72974 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -211,10 +211,9 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	const struct file_operations *fops = &io_mock_fops;
 	const struct io_uring_sqe *sqe = cmd->sqe;
 	struct io_uring_mock_create mc, __user *uarg;
-	struct io_mock_file *mf = NULL;
-	struct file *file = NULL;
+	struct file *file;
+	struct io_mock_file *mf __free(kfree) = NULL;
 	size_t uarg_size;
-	int fd = -1, ret;
 
 	/*
 	 * It's a testing only driver that allows exercising edge cases
@@ -246,10 +245,6 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	if (!mf)
 		return -ENOMEM;
 
-	ret = fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
-	if (fd < 0)
-		goto fail;
-
 	init_waitqueue_head(&mf->poll_wq);
 	mf->size = mc.file_size;
 	mf->rw_delay_ns = mc.rw_delay_ns;
@@ -258,33 +253,25 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 		mf->pollable = true;
 	}
 
-	file = anon_inode_create_getfile("[io_uring_mock]", fops,
-					 mf, O_RDWR | O_CLOEXEC, NULL);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
-		goto fail;
-	}
+	FD_PREPARE(fdf, O_RDWR | O_CLOEXEC,
+		   anon_inode_create_getfile("[io_uring_mock]", fops, mf,
+					     O_RDWR | O_CLOEXEC, NULL));
+	if (fdf.err)
+		return fdf.err;
 
-	file->f_mode |= FMODE_READ | FMODE_CAN_READ |
-			FMODE_WRITE | FMODE_CAN_WRITE |
-			FMODE_LSEEK;
+	retain_and_null_ptr(mf);
+	file = fd_prepare_file(fdf);
+	file->f_mode |= FMODE_READ | FMODE_CAN_READ | FMODE_WRITE |
+			FMODE_CAN_WRITE | FMODE_LSEEK;
 	if (mc.flags & IORING_MOCK_CREATE_F_SUPPORT_NOWAIT)
 		file->f_mode |= FMODE_NOWAIT;
 
-	mc.out_fd = fd;
-	if (copy_to_user(uarg, &mc, uarg_size)) {
-		fput(file);
-		ret = -EFAULT;
-		goto fail;
-	}
+	mc.out_fd = fd_prepare_fd(fdf);
+	if (copy_to_user(uarg, &mc, uarg_size))
+		return -EFAULT;
 
-	fd_install(fd, file);
+	fd_publish(fdf);
 	return 0;
-fail:
-	if (fd >= 0)
-		put_unused_fd(fd);
-	kfree(mf);
-	return ret;
 }
 
 static int io_probe_mock(struct io_uring_cmd *cmd)