Re: [PATCH v3] zram: try vmalloc() after kmalloc()

[Minchan Kim <minchan@kernel.org>]

On Tue, Nov 24, 2015 at 10:06:22AM +0900, Sergey Senozhatsky wrote:
> On (11/24/15 09:35), Minchan Kim wrote:
> [..]
> > > We can use __GFP_RECLAIM (used to be __GFP_WAIT).  That permits the
> > > allocation to wait for in-flight IO to complete and to reclaim clean
> > > pagecache.
> > 
> > Generally, you're right but in case of zram, it would be unfortunate.
> > 
> > It would be void *most of time* because it is called in reclaim context
> > and reclaim path bails out to avoid recursion of direct reclaim
> > by PF_MEMALLOC without trying reclaim.
> > However, the reason I said *most of time* is we has another context
> > the funcion could be called.
> > 
> >         "disksize_store"->zcomp_create
> > 
> > In the place, we should make sure the successful allocation to work
> > zram at least so that path should use another gfp.
> > I will work for that.
> 
> Hm... is it really worth it? passing a bool to zcomp_strm_alloc() (so
> it can decide what gfp flags to use) or gfp flags directly is just a
> bit complicated. what's the problem with GFP_NOIO (__GFP_RECLAIM) in
> the first place (sorry if I'm missing something terribly obvious)?

No, you didn't miss anything and your question is really proper.
Actually, I was on same page with you but when I think more,
I guess it makes code looks clean and right way for structuring, IMO.
So, I coded now and am preasure with it. I hope you are on same
page when you look at new patchset. :)

> 
> alternatively, we can just remove the 'dynamic' streams allocation part
> and allocate all of the streams via sysfs store path only.

Hmm, I don't think it's really trouble part we cannot fix easily
so let's stay with it!


> 
> 	-ss

-- 
Kind regards,
Minchan Kim