Re: [Bug 192571] zswap + zram enabled BUG

[Michal Hocko <mhocko@kernel.org>]

On Wed 18-01-17 10:39:48, Sergey Senozhatsky wrote:
> Cc Dan
> 
> On (01/17/17 12:22), Andrew Morton wrote:
> > > https://bugzilla.kernel.org/show_bug.cgi?id=192571
> > > 
> > > --- Comment #1 from Gluzskiy Alexandr <sss123next@list.ru> ---
> > > [199961.576604] ------------[ cut here ]------------
> > > [199961.577830] kernel BUG at mm/zswap.c:1108!
> 
> zswap didn't manage to decompress the page:
> 
> static int zswap_frontswap_load(unsigned type, pgoff_t offset,
> 				struct page *page)
> {
> ...
> 	dst = kmap_atomic(page);
> 	tfm = *get_cpu_ptr(entry->pool->tfm);
> 	ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
> 	put_cpu_ptr(entry->pool->tfm);
> 	kunmap_atomic(dst);
> 	zpool_unmap_handle(entry->pool->zpool, entry->handle);
> 	BUG_ON(ret);
> 	^^^^^^^^^^^

Ugh, why do we even do that? This is not the way how to handle error
situations. AFAIU propagating the error out wouldn't be a big deal
because we would just fallback to regular swap, right?
-- 
Michal Hocko
SUSE Labs

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