dax: fix build warnings with FS_DAX and !FS_IOMAP

As reported by Arnd:

  https://lkml.org/lkml/2017/1/10/756

Compiling with the following configuration:

  # CONFIG_EXT2_FS is not set
  # CONFIG_EXT4_FS is not set
  # CONFIG_XFS_FS is not set
  # CONFIG_FS_IOMAP depends on the above filesystems, as is not set
  CONFIG_FS_DAX=y

generates build warnings about unused functions in fs/dax.c:

  fs/dax.c:878:12: warning: `dax_insert_mapping' defined but not used [-Wunused-function]
   static int dax_insert_mapping(struct address_space *mapping,
              ^~~~~~~~~~~~~~~~~~
  fs/dax.c:572:12: warning: `copy_user_dax' defined but not used [-Wunused-function]
   static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
              ^~~~~~~~~~~~~
  fs/dax.c:542:12: warning: `dax_load_hole' defined but not used [-Wunused-function]
   static int dax_load_hole(struct address_space *mapping, void **entry,
              ^~~~~~~~~~~~~
  fs/dax.c:312:14: warning: `grab_mapping_entry' defined but not used [-Wunused-function]
   static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
                ^~~~~~~~~~~~~~~~~~

Now that the struct buffer_head based DAX fault paths and I/O path have
been removed we really depend on iomap support being present for DAX.
Make this explicit by selecting FS_IOMAP if we compile in DAX support.

This allows us to remove conditional selections of FS_IOMAP when FS_DAX
was present for ext2 and ext4, and to remove an #ifdef in fs/dax.c.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ross Zwisler <[email protected]>
Reported-by: Arnd Bergmann <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions