Hi Herbert,
On Sun, Nov 13, 2016 at 07:45:32PM +0800, Herbert Xu wrote:
> +int skcipher_walk_done(struct skcipher_walk *walk, int err)
> +{
> + unsigned int nbytes = 0;
> + unsigned int n = 0;
> +
> + if (likely(err >= 0)) {
> + n = walk->nbytes - err;
> + nbytes = walk->total - n;
> + }
> +
> + if (likely(!(walk->flags & (SKCIPHER_WALK_PHYS |
> + SKCIPHER_WALK_SLOW |
> + SKCIPHER_WALK_COPY |
> + SKCIPHER_WALK_DIFF)))) {
> +unmap_src:
> + skcipher_unmap_src(walk);
Isn't it wrong to unmap the buffers when err < 0? They won't have been mapped
yet, e.g. if the 'skcipher_walk_done(walk, -EINVAL)' case is hit.
> + /* Short-circuit for the common/fast path. */
> + if (!(((unsigned long)walk->iv ^ (unsigned long)walk->oiv) |
> + ((unsigned long)walk->buffer ^ (unsigned long)walk->page) |
> + (unsigned long)walk->page))
> + goto out;
This is really saying that the IV wasn't copied and that walk->buffer and
walk->page are both NULL. But if walk->buffer is NULL then the IV wasn't
copied. So this can be simplified to:
if (!((unsigned long)walk->buffer | (unsigned long)walk->page))
goto out;
> +int skcipher_walk_next(struct skcipher_walk *walk)
> +{
Shouldn't this be static? There's even a static declaration earlier in the
file.
> +static int skcipher_next_slow(struct skcipher_walk *walk)
> +{
> + bool phys = walk->flags & SKCIPHER_WALK_PHYS;
> + unsigned alignmask = walk->alignmask;
> + unsigned bsize = walk->chunksize;
...
> + walk->nbytes = bsize;
skcipher_next_slow() is always setting up 'chunksize' bytes to be processed.
Isn't this wrong in the 'blocksize < chunksize' case because fewer than
'chunksize' bytes may need to be processed?
> +static inline void *skcipher_map(struct scatter_walk *walk)
> +{
> + struct page *page = scatterwalk_page(walk);
> +
> + return (PageHighMem(page) ? kmap_atomic(page) : page_address(page)) +
> + offset_in_page(walk->offset);
> +}
Is the PageHighMem() optimization really worthwhile? It will skip kmap_atomic()
and hence preempt_disable() for non-highmem pages, so it may make it harder to
find bugs where users are sleeping when they shouldn't be. It also seems
inconsistent that skcipher_map() will do this optimization but scatterwalk_map()
won't.
> + if (!walk->page) {
> + gfp_t gfp = skcipher_walk_gfp(walk);
> +
> + walk->page = (void *)__get_free_page(gfp);
> + if (!walk->page)
> + goto slow_path;
> + }
> +
> + walk->nbytes = min_t(unsigned, n,
> + PAGE_SIZE - offset_in_page(walk->page));
walk->page will be page-aligned, so there's no need for offset_in_page(). Also,
'n' has already been clamped to at most one page. So AFAICS this can simply be
'walk->nbytes = n;'.
> +int skcipher_walk_done(struct skcipher_walk *walk, int err);
...
> +void skcipher_walk_complete(struct skcipher_walk *walk, int err);
The naming is confusing: "done" vs. "complete". They can easily be mixed up.
Would it make more sense to have something with "async" in the name for the
second one, like skcipher_walk_async_done()?
Eric
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