linux-kernel - Re: [PATCH] mm,memory_hotplug: Fix scan_movable

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Message-ID: <20190123102242.GT4087@dhcp22.suse.cz>
Date:   Wed, 23 Jan 2019 11:22:42 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, david@...hat.com
Subject: Re: [PATCH] mm,memory_hotplug: Fix scan_movable_pages for gigantic
 hugepages

On Wed 23-01-19 11:18:42, Oscar Salvador wrote:
> On Wed, Jan 23, 2019 at 10:47:17AM +0100, Michal Hocko wrote:
> > So this should be probably folded into the above patch as it is
> > incomplete unless I am missing something.
> 
> Well, they are triggered from different paths.
> The former error was triggered in:
> 
> removable_show
>  is_mem_section_removable
>   is_pageblock_removable_nolock
>    has_unmovable_pages
> 
> while this one is triggered when actually doing the offline operation

But it would trigger from the offline path as well, no?

> __offline_pages
>  scan_movable_pages
>  
> But I do agree that one without the other is not really useful, an incomplete.
> The truth is that I did not spot this one when fixing [1] because I did not
> really try to offline the memblock back then, so my fault.

I should have noticed that during the review but those paths are really
far away from each other so this is hard to spot indeed

> While I agree that the best approach would be to fold this one into [1],
> I am not sure if it is too late for that as it seems that [1] was already
> released into mainline, and moreover to stable.

OK, I wasn't aware of that. Then my suggestion is clearly moot.

> I guess I will have Andrew decide what is the best way to carry on here.
> 
> [1] https://patchwork.kernel.org/patch/10739963/
> 
> > 
> > > Signed-off-by: Oscar Salvador <osalvador@...e.de>
> > 
> > Other than that the change looks good to me.
> > 
> > Acked-by: Michal Hocko <mhocko@...e.com>
> 
> Thanks!
> -- 
> Oscar Salvador
> SUSE L3

-- 
Michal Hocko
SUSE Labs