Re: [PATCH 1/2] Block layer filter - second version

[Matthew Wilcox]

On Wed, Oct 21, 2020 at 09:21:36AM +0000, Damien Le Moal wrote:
> > + * submit_bio_direct - submit a bio to the block device layer for I/O
> > + * bypass filter.
> > + * @bio:  The bio describing the location in memory and on the device.
> >   *
> > + * Description:

You don't need this line.

> > + *    This is a version of submit_bio() that shall only be used for I/O
> > + *    that cannot be intercepted by block layer filters.
> > + *    All file systems and other upper level users of the block layer
> > + *    should use submit_bio() instead.
> > + *    Use this function to access the swap partition and directly access
> > + *    the block device file.

I don't understand why O_DIRECT gets to bypass the block filter.  Nor do
I understand why anybody would place a block filter on the swap device.
But if somebody did place a filter on the swap device, why should swap
be able to bypass the filter?