Re: A proposal for making ext4's journal more SMR (and flash) friendly

[Theodore Ts'o <tytso@mit.edu>]

On Wed, Jan 08, 2014 at 11:14:30PM +0100, Jan Kara wrote:
>   So when I was thinking about this (already couple of years ago) the thing
> which stopped me was the question at which layer we should do the
> translation. Ideally we would need something at submit_bh() level but just
> wrapping submit_bh() calls inside ext4 isn't enough for stuff like symlinks
> or journalled data... Do you have any thoughts on that?

I think there are two interfaces that should handle nearly all of our
journal block mapping needs.  The functions that issue bio requests
directly tend to use ext4_get_block*() functions, and functions which
use the buffer cache uses submit_bh() (typically via ext4_getblk).
There will probably be a few exceptions, but I don't think this should
be an intractable problem.

Regards,

					- Ted