Alexey,

It'd be helpful to me to understand _why_ this use case is important
for your workloads.  O_DIRECT support is rarely used as far as I know,
and fs blocksize != page size is rare as well.  The main use cases I
know of fs blocksize != page size is on architectures (not terribly
common) with 16k or 64k page sizes, that want to use 4k file system
blocksizes for interoperability reasons.

(And I suppose because mke2fs uses a 4k block size by default.  Perhaps
we should change this so that the default is that mke2fs will use a
block size == page size, unless for some reason the page size is not
one supported by ext4 (although I'm not aware of any architecture
wanting page sizes > 64k), or the user explicitly specifies the block
size using "mke2fs -b".)

Are you trying to make O_DIRECT support in e2fsprogs a first class
reason out of completeness concern?  Or is this a use case which is
important in production workloads that you are familiar with?

Thanks,

						- Ted