Re: [PATCH 6/7] writeback: separate starting of sync vsopportunistic writeback

[Christoph Hellwig]

On Mon, Sep 14, 2009 at 03:33:07PM +0200, Jan Kara wrote:
> On Mon 14-09-09 11:36:33, Jens Axboe wrote:
> > bdi_start_writeback() is currently split into two paths, one for
> > WB_SYNC_NONE and one for WB_SYNC_ALL. Add bdi_sync_writeback()
> > for WB_SYNC_ALL writeback and let bdi_start_writeback() handle
> > only WB_SYNC_NONE.
>   What I don't like about this patch is that if somebody sets up
> writeback_control with WB_SYNC_ALL mode set and then submits it to disk via
> bdi_start_writeback() it will just silently convert his writeback to an
> asynchronous one.
>   So I'd maybe leave setting of sync_mode to the caller and just WARN_ON if
> it does not match the purpose of the function...

Or initialize the wb entirely inside these functions.  For the sync case
we really only need a superblock as argument, and for writeback it's
bdi + nr_pages.  And also make sure they consistenly return void as
no one cares about the return value.

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