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Date:   Wed, 13 Apr 2022 13:26:06 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     Vlastimil Babka <vbabka@suse.cz>, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
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        Pedro Gomes <pedrodemargomes@gmail.com>,
        Oded Gabbay <oded.gabbay@gmail.com>, linux-mm@kvack.org
Subject: Re: [PATCH v3 08/16] mm/rmap: drop "compound" parameter from
 page_add_new_anon_rmap()
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On Tue, Apr 12, 2022 at 11:37:09AM +0200, David Hildenbrand wrote:
> On 12.04.22 10:47, Vlastimil Babka wrote:
> > There's a VM_BUG_ON_PAGE(PageTransCompound(page), page); later in a
> > !compound branch. Since compound is now determined by the same check, could
> > be deleted.
> 
> Yes, eventually we could get rid of both VM_BUG_ON_PAGE() on both
> branches and add a single VM_BUG_ON_PAGE(PageTail(page), page) check on
> the compound branch. (we could also make sure that we're not given a
> hugetlb page)

As a rule of thumb, if you find yourself wanting to add
VM_BUG_ON_PAGE(PageTail(page), page), you probably want to change the
interface to take a folio.