On (01/18/17 20:36), Dan Streetman wrote:

On Wed, Jan 18, 2017 at 8:17 AM, Michal Hocko [off-list ref] wrote:

quoted

On Wed 18-01-17 10:39:48, Sergey Senozhatsky wrote:

quoted

Cc Dan

On (01/17/17 12:22), Andrew Morton wrote:

quoted

quoted

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?

yeah this function definitely should never bug; it's just a callback
from the zpool to try to write a page back to the swapcache so the
zpool can free a page.  It's definitely ok for it to return an error.

good. Dan, Seth, care to send the patch?
and one more thing... can you take a look at [1]?

[1] https://marc.info/?l=linux-mm&m=147031191906154&w=4

	-ss

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