svn commit: r221166 - in head/sys: fs/ext2fs modules/ext2fs

[Pedro F. Giffuni]

> There is no dependencies for ext2fs, the FFS comments talks about SU.

You are right ... I will have to clean that up. It was not easy to
keep all SU stuff from getting in.

> Also, I am unsure what the resulting semantic of O_DIRECTIO for ext2
> is ? UFS tries to eliminate any use of buffer cache for O_DIRECTIO
> case, up to the mapping of user pages into pbuf to perform the
> actual i/o. In ext2 case, it seems we will just destroy the buffers
> after using them for i/o. Is it useful ?

We do not support the complete direct_io stuff (not even in UFS).
In ext2fs we are only avoiding double caching: it is assumed that
the application (usually databases) knows why it's setting
O_DIRECTIO and do their own caching. From what I discussed
with Tor Egge it is useful.

cheers,

Pedro.