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Date:   Tue, 29 Aug 2023 15:19:29 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Ryan Roberts <ryan.roberts@arm.com>
Cc:     Will Deacon <will@kernel.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Yu Zhao <yuzhao@google.com>,
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        Yin Fengwei <fengwei.yin@intel.com>,
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        "Huang, Ying" <ying.huang@intel.com>, Zi Yan <ziy@nvidia.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 4/4] mm/mmu_gather: Store and process pages in contig
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On Tue, Aug 29, 2023 at 03:02:22PM +0100, Ryan Roberts wrote:
> >> +			if (put_devmap_managed_page(&folio->page))
> >> +				continue;
> >> +			if (folio_put_testzero(folio))
> > 
> > We're only putting one ref for the zone_device folios?  Surely
> > this should be ref_sub_and_test like below?
> 
> Good point. This function is originally a copy/paste of release_pages(), and I
> obviously missed this. In fact, looking at it again today, I think I'll factor
> out the vast majority into a common helper, since I'm currently duplicating a
> whole bunch here.
> 
> In practice I think all devmap folios will be small today though? So while I
> agree I need to fix this, I think in practice it will currently do the right thing?

I think the devdax code uses 2MB folios.

> > You'll be glad to know I've factored out a nice little helper for that.
> 
> OK, what's it called? This is just copied from release_pages() at the moment.
> Happy to use your helper in the refactored common helper.

I'll send out those patches today.