Re: [PATCH v4 1/9] mmc: add basic support for inline encryption

[Eric Biggers <ebiggers@kernel.org>]

On Tue, Jan 19, 2021 at 12:52:00PM -0800, Eric Biggers wrote:
> > To free up the data structures, blk_ksm_destroy() is called from
> > mmc_free_host().
> > 
> > To me, this can be made more consistent. For example, it looks like
> > blk_ksm_destroy() could be called, even if blk_ksm_init() hasn't been
> > called (depending on the probe error path of the mmc host).
> 
> blk_ksm_destroy() is a no-op on an all-zeroed struct, so it's fine to call it
> unnecessarily.  We could call it unconditionally, if that would be clearer.
> 
> > There are a couple of options to better deal with this.
> > 1) Extend the blk_ksm interface with a devm_blk_ksm_init() function
> > (thus let it deal with lifecycle problems for us) and simply drop the
> > call to blk_ksm_destroy().
> 
> This would require adding APIs to devm to support zeroing buffers on free and to
> use kvmalloc() instead of kmalloc().  It looks like these new APIs wouldn't be
> useful for many drivers (since almost everyone else just wants regular kmalloc
> with no special behavior on free), so they don't seem worth adding yet.

Actually devres is more flexible than I thought; it's possible to register
custom actions to be executed.  I'll send out a patchset that adds
devm_blk_ksm_init() and converts the UFS driver to use it.

- Eric