linux-kernel - Re: [PATCH] mm/page_alloc: fix memalloc_nocma

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Message-ID: <20200721124312.GE15516@casper.infradead.org>
Date:   Tue, 21 Jul 2020 13:43:12 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     js1304@...il.com, Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-team@....com, Christoph Hellwig <hch@...radead.org>,
        Roman Gushchin <guro@...com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Michal Hocko <mhocko@...e.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, stable@...r.kernel.org
Subject: Re: [PATCH] mm/page_alloc: fix memalloc_nocma_{save/restore} APIs

On Tue, Jul 21, 2020 at 02:38:56PM +0200, Vlastimil Babka wrote:
> On 7/21/20 2:05 PM, Matthew Wilcox wrote:
> > On Tue, Jul 21, 2020 at 12:28:49PM +0900, js1304@...il.com wrote:
> >> @@ -4619,8 +4631,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >>  		wake_all_kswapds(order, gfp_mask, ac);
> >>  
> >>  	reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
> >> -	if (reserve_flags)
> >> +	if (reserve_flags) {
> >>  		alloc_flags = reserve_flags;
> >> +		alloc_flags = current_alloc_flags(gfp_mask, alloc_flags);
> >> +	}
> > 
> > Is this right?  Shouldn't you be passing reserve_flags to
> > current_alloc_flags() here?  Also, there's no need to add { } here.
> 
> Note the "alloc_flags = reserve_flags;" line is not being deleted here. But if
> it was, your points would be true, and yeah it would be a bit more tidy.

Oh ... I should wake up a little more.

Yeah, I'd recommend just doing this:

-		alloc_flags = reserve_flags;
+		alloc_flags = current_alloc_flags(gfp_mask, reserve_flags);