On Tue, Nov 29, 2016 at 09:53:03AM +0100, Jan Kara wrote:

On Mon 28-11-16 12:15:04, Ross Zwisler wrote:

quoted

On Thu, Nov 24, 2016 at 10:02:39AM +0100, Jan Kara wrote:

quoted

On Wed 23-11-16 11:44:17, Ross Zwisler wrote:

quoted

With the current Kconfig setup it is possible to have the following:

CONFIG_EXT4_FS=y
CONFIG_FS_DAX=y
CONFIG_FS_IOMAP=n	# this is in fs/Kconfig & isn't user accessible

With this config we get build failures in ext4_dax_fault() because the
iomap functions in fs/dax.c are missing:

fs/built-in.o: In function `ext4_dax_fault':
file.c:(.text+0x7f3ac): undefined reference to `dax_iomap_fault'
file.c:(.text+0x7f404): undefined reference to `dax_iomap_fault'
fs/built-in.o: In function `ext4_file_read_iter':
file.c:(.text+0x7fc54): undefined reference to `dax_iomap_rw'
fs/built-in.o: In function `ext4_file_write_iter':
file.c:(.text+0x7fe9a): undefined reference to `dax_iomap_rw'
file.c:(.text+0x7feed): undefined reference to `dax_iomap_rw'
fs/built-in.o: In function `ext4_block_zero_page_range':
inode.c:(.text+0x85c0d): undefined reference to `iomap_zero_range'

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.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

I've sent the same patch to Ted yesterday and he will probably queue it on
top of ext4 iomap patches. If it doesn't happen for some reason, feel free
to add:

Reviewed-by: Jan Kara <redacted>

Cool, looks like Ted has pulled in your patch.

I think we still eventually want this patch because it cleans up our handling
of FS_IOMAP.  With your patch we select it separately in both ext4 & ext2
based on whether we include DAX, and we still have #ifdefs in fs/dax.c for
FS_IOMAP.

Actually, based on Dave's request I've also sent Ted updated version which
did select FS_IOMAP in CONFIG_DAX section. However Ted didn't pull that
patch (yet?). Anyway, I don't care whose patch gets merged, I just wanted
to notify you of possible conflict.

Can you please CC me on these patches in the future?  I also don't care whose
patches end up fixing this, but I want to make sure we end up in a world where
the "select FS_IOMAP" just happens directly for FS_DAX in fs/Kconfig so that
I can get rid of the unnecessary #ifdefs in fs/dax.c for CONFIG_FS_IOMAP.