nilfs2: make splice write available again

commit a35d8f016e0b68634035217d06d1c53863456b50 upstream.

Since 5.10, splice() or sendfile() to NILFS2 return EINVAL.  This was
caused by commit 36e2c74 ("fs: don't allow splice read/write
without explicit ops").

This patch initializes the splice_write field in file_operations, like
most file systems do, to restore the functionality.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Joachim Henke <[email protected]>
Signed-off-by: Ryusuke Konishi <[email protected]>
Tested-by: Ryusuke Konishi <[email protected]>
Cc: <[email protected]>	[5.10+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

fs/nilfs2/file.c

@@ -141,6 +141,7 @@ const struct file_operations nilfs_file_operations = {
  /* .release = nilfs_release_file, */
  .fsync = nilfs_sync_file,
  .splice_read = generic_file_splice_read,
+ .splice_write = iter_file_splice_write,
 };
 
 const struct inode_operations nilfs_file_inode_operations = {