From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1414F430CF1 for ; Tue, 7 Jul 2026 14:18:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783433938; cv=none; b=CEVydYW/+SWVQErICwPQDV3wSYsJGDFCNVefYLvIXAkxrPyjjQDz1pZnVDJAajWVGQnz3+mPTsHR/MKK9PfMLMdPs0AcoATryf8nlfbKcU/nE8+qKdNwds4LgV+Qf9X8NatjA1pZp3ceIONKls0abFzhteT95aNXwGzJPsbD01g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783433938; c=relaxed/simple; bh=tniM0Q5G8JpiNFiEHOI82ySrFKwl7sQUwjz0/mxdz0w=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lJ5B3bqDvn5IXLZtOkCl8251T2KKqvfGU/o3BYWJ09KiBSEA4Dr0K0dsK3eLbwMx1uc5CVC6TNlFjxVSyoovV6kuB1mXdi7T34bK6l2KVSU7USzF3K0MmQYlQejbokgjcueMNYM6Mv+rJeSjHAZx8ufAQVH5gb9fr8LQiglj/Fs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nmiYEDXk; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nmiYEDXk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C254C1F00A3D; Tue, 7 Jul 2026 14:18:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783433936; bh=ktqpqtiz95PjMFN81dPctsXJOWOULvpc2/aL54me+as=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=nmiYEDXkEZnSOwyL9BvX8iVgZm3W9BGDeHjceORW9SrFJc3D/Iqs1IIu73Xg36lUK 3sJWnyNIJNbPOHvhlrneVotAiUPcsKX3VdGovD4afEX+8CJ5KRVaogopZUy6WPVVdE 0olwgM1nHW2a9dY2JWdS0poCxRgSjomO394fPG3MWtxjzSD3LbZVyDmM4V+JIWWcYn FB9oYXmlWOYGaSdF7WeVqjn6zgNipkrxq+tLEMOx+vYsWwl06FriYDDJCgBKyqf4KH hEBOlReb1TwGqGEYNFi3dWZvzEDCV+g9Ym2EonfBAqq40HfnK5GbDjzak/vuHsFKa5 fYh2uO5sVRevw== Message-ID: <22fb2f54-da23-40b2-91f5-aeaf54037bcd@kernel.org> Date: Tue, 7 Jul 2026 16:18:52 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/5] mm/rmap: refactor some code around lazyfree folio unmapping To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org, muchun.song@linux.dev, osalvador@suse.de Cc: riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260707121128.373192-1-dev.jain@arm.com> <20260707121128.373192-4-dev.jain@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/7/26 14:11, Dev Jain wrote: > For lazyfree folio unmapping, after clearing the ptes we must abort the > operation if the folio got dirtied or it has unexpected references. > > Refactor this logic into a function which will return whether we need > to abort or not. > > If we abort, we restore the ptes and bail out of try_to_unmap_one. > Otherwise adjust the rss stats of the mm and jump to a label. > > Also rename that label from "discard" to "finish_unmap"; the former > is appropriate in the lazyfree context, but the code following the label > is executed for other successful unmap code paths too, so 'discard' does > not sound correct for them. > > No functional change intended. > > Signed-off-by: Dev Jain > --- > mm/rmap.c | 87 +++++++++++++++++++++++++++++++------------------------ > 1 file changed, 49 insertions(+), 38 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index 934773dfa2f2a..00b571c2a1bab 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2067,6 +2067,52 @@ static bool try_to_unmap_hugetlb_one(struct folio *folio, > return ret; > } > > +static inline bool ttu_anon_lazyfree_folio(struct vm_area_struct *vma, > + struct folio *folio) > +{ > + int ref_count, map_count; > + > + /* > + * Synchronize with gup_pte_range(): > + * - clear PTE; barrier; read refcount > + * - inc refcount; barrier; read PTE > + */ > + smp_mb(); > + > + ref_count = folio_ref_count(folio); > + map_count = folio_mapcount(folio); > + > + /* > + * Order reads for page refcount and dirty flag > + * (see comments in __remove_mapping()). > + */ > + smp_rmb(); > + > + if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) { > + /* > + * redirtied either using the page table or a previously > + * obtained GUP reference. > + */ > + folio_set_swapbacked(folio); > + return false; > + } > + > + if (ref_count != 1 + map_count) { > + /* > + * Additional reference. Could be a GUP reference or any > + * speculative reference. GUP users must mark the folio > + * dirty if there was a modification. This folio cannot be > + * reclaimed right now either way, so act just like nothing > + * happened. > + * We'll come back here later and detect if the folio was > + * dirtied when the additional reference is gone. > + */ > + return false; > + } > + > + return true; You could simply do /* * Additional references could be due to GUP or from a speculative * lookup. ... */ return ref_count == 1 + map_count; Nothing else jumped at me Acked-by: David Hildenbrand (Arm) -- Cheers, David