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, 17 insertions, 39 deletions

diff --git a/fs/xfs/xfs_handle.c b/fs/xfs/xfs_handle.c
index f19fce557354..5a3e3bf4e7cc 100644
--- a/fs/xfs/xfs_handle.c
+++ b/fs/xfs/xfs_handle.c
@@ -233,14 +233,11 @@ xfs_open_by_handle(
 	xfs_fsop_handlereq_t	*hreq)
 {
 	const struct cred	*cred = current_cred();
-	int			error;
-	int			fd;
 	int			permflag;
-	struct file		*filp;
 	struct inode		*inode;
 	struct dentry		*dentry;
 	fmode_t			fmode;
-	struct path		path;
+	struct path		path __free(path_put) = {};
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -249,12 +246,11 @@ xfs_open_by_handle(
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 	inode = d_inode(dentry);
+	path.dentry = dentry;
 
 	/* Restrict xfs_open_by_handle to directories & regular files. */
-	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))) {
-		error = -EPERM;
-		goto out_dput;
-	}
+	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
+		return -EPERM;
 
 #if BITS_PER_LONG != 32
 	hreq->oflags |= O_LARGEFILE;
@@ -263,48 +259,30 @@ xfs_open_by_handle(
 	permflag = hreq->oflags;
 	fmode = OPEN_FMODE(permflag);
 	if ((!(permflag & O_APPEND) || (permflag & O_TRUNC)) &&
-	    (fmode & FMODE_WRITE) && IS_APPEND(inode)) {
-		error = -EPERM;
-		goto out_dput;
-	}
+	    (fmode & FMODE_WRITE) && IS_APPEND(inode))
+		return -EPERM;
 
-	if ((fmode & FMODE_WRITE) && IS_IMMUTABLE(inode)) {
-		error = -EPERM;
-		goto out_dput;
-	}
+	if ((fmode & FMODE_WRITE) && IS_IMMUTABLE(inode))
+		return -EPERM;
 
 	/* Can't write directories. */
-	if (S_ISDIR(inode->i_mode) && (fmode & FMODE_WRITE)) {
-		error = -EISDIR;
-		goto out_dput;
-	}
+	if (S_ISDIR(inode->i_mode) && (fmode & FMODE_WRITE))
+		return -EISDIR;
 
-	fd = get_unused_fd_flags(0);
-	if (fd < 0) {
-		error = fd;
-		goto out_dput;
-	}
+	path.mnt = mntget(parfilp->f_path.mnt);
 
-	path.mnt = parfilp->f_path.mnt;
-	path.dentry = dentry;
-	filp = dentry_open(&path, hreq->oflags, cred);
-	dput(dentry);
-	if (IS_ERR(filp)) {
-		put_unused_fd(fd);
-		return PTR_ERR(filp);
-	}
+	FD_PREPARE(fdf, 0, dentry_open(&path, hreq->oflags, cred));
+	if (fdf.err)
+		return fdf.err;
 
 	if (S_ISREG(inode->i_mode)) {
+		struct file *filp = fd_prepare_file(fdf);
+
 		filp->f_flags |= O_NOATIME;
 		filp->f_mode |= FMODE_NOCMTIME;
 	}
 
-	fd_install(fd, filp);
-	return fd;
-
- out_dput:
-	dput(dentry);
-	return error;
+	return fd_publish(fdf);
 }
 
 int