Re: [Bug 192571] zswap + zram enabled BUG

[Chulmin Kim <cmlaika.kim@samsung.com>]

On 01/24/2017 03:16 PM, Dan Streetman wrote:
> On Mon, Jan 23, 2017 at 7:03 PM, Alexandr <sss123next@list.ru> wrote:
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>>
>>> Why would you do this?  There's no benefit of using zswap together
>>> with zram.
>>
>> i just wanted to test zram and zswap, i still not dig to deep in it,
>> but what i wanted is to use zram swap (with zswap disabled), and if it
>> exceeded use real swap on block device with zswap enabled.
>
> I don't believe that's possible, you can't enable zswap for only
> specific swap devices; and anyway, if you fill up zram, you won't
> really have any memory left for zswap to use will you?
>
> However, it shouldn't encounter any BUG(), like you saw.  If it's
> reproducable for you, can you give details on how to reproduce it?
>

Hello. Mr. Streetman.


Regarding to this problem, I have a question on zswap.

Is there any reason that
zswap_frontswap_load() does not call flush_dcache_page()?

The zswap load function can dirty the page mapped to user space (might 
be shareable/writable) which seems exactly the condition mentioned in 
the definition of flush_dcache_page().

I'm thinking that
flush_dcache_page() should be called in the end of zswap_frontswap_load().
Could you review my opinion?

Thanks!
Chulmin Kim








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