Re: [Lsf] IO less throttling and cgroup aware writeback

Vivek Goyal
2011-04-07T21:35:07Z

On Thu, Apr 07, 2011 at 04:33:03PM -0400, Christoph Hellwig wrote:
> On Thu, Apr 07, 2011 at 03:24:24PM -0400, Vivek Goyal wrote:
> > IIUC, so first we need to fix existing code where we seem to be moving
> > any inode on bdi writeback list based on I_DIRTY flag.
>
> I_DIRTY is a set of flags. Inodes are on the dirty list if any of
> the flags is set.
>
> > BTW, what's the difference between I_DIRTY_DATASYNC and I_DIRTY_PAGES? To
> > me both seem to mean that data needs to be written back and not the
> > inode itself.
>
> I_DIRTY_PAGES means dirty data (pages)
> I_DIRTY_DATASYNC means dirty metadata which needs to be written for fdatasync
> I_DIRTY_SYNC means dirty metadata which only needs to be written for fsync

Ok, that helps. Thanks. So an fdatasync() can write back some metadata
too if I_DIRTY_DATASYNC is set.

Thanks
Vivek