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imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=nmiYEDXk; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf29.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1783433937; b=QnC3FytOStE/U/6dZMUnv4VCdqD2513d+/YyZS497E7tr4Qwld15M944K4s+STTEGKiHpv jbXB+CS0+SH3AmJPbEM/FwOxdm1524HS5TFdimrH8xt7kdxZD4PoU5uOTWzN0BG1VdhtLo qFmMZl2OIN+9j92TKqIUDH5eE+bng04= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 3D019618B6; Tue, 7 Jul 2026 14:18:57 +0000 (UTC) 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 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 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A4457120005 X-Stat-Signature: d8wurt6mdf3yw4669bqgrrisqhdp1sdp X-HE-Tag: 1783433937-532239 X-HE-Meta: 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 kh1rataw KU8jn4E1/0mOBtbUwYhcebUqCdSmCR04cR4c8+QBnZ7MQbP8xawgsUq7EtuSwmy8byGpL1SiFN1K92nIeDNUs1uPMs430UyFX/xQnRyVA59kRCLxchACGjso7iCY1wZT6uITrDVzft3mnLCxaHSRiYTVsBpxwxyk0DCgqZdeCte540VwF4Rr9soIUJs2rH37Lu5p83KZu46PVfdSj8cCkzh/oaiDgiM86ZwwD/CPrWHDA6J2zdZL77jQav/3OQIFf8FotuoqoNp/gpi9KAcQkUBOdZ3acrXE8fxJeZFtbjDfSIIOKkmaHZlUBiUDtlNd5CJzFtlp0+LDN+acq/FwrhwDuug== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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