From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 608E0478E27; Fri, 27 Feb 2026 20:11:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772223098; cv=none; b=pnxmZrU0VPfIfar41Wy/2dfSYflfpX/dVe2m/iH+QQ78bx0PodPW++oAJzeKTdsbwnB3JKkV8+Ro/TVFX14RVKIdiAohHBzjGmAEVhDegt1BOpwoP/wxiwwOytoGX1r4iYE0LcmFR76c45muiOpDpstr5B52qXlEtiBPKVBLouQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772223098; c=relaxed/simple; bh=KcfCcPy+dBQFq2iZWWRAzMkc9iA3mhQIqe4VKvKm/84=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Es3tNLruDZ8BRldSbrztSDLpD95RQYXczH+wkVwMDCaB0UMMbu2ST5bcqF7cdhrt3m42B49q99q/Azv3vfFVEPJbOVx8sExf7zi86DeEZHoG+GkgWykwaSyhx2C+6Pu9m/N02pdrR3dJybk8K7R5ADxMPQChpaadBZtqk/ZNZVg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R+uZFzLt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R+uZFzLt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C83C0C2BC86; Fri, 27 Feb 2026 20:11:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772223098; bh=KcfCcPy+dBQFq2iZWWRAzMkc9iA3mhQIqe4VKvKm/84=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R+uZFzLtdrG65b8hmVxNKYNlrS/AesJe5C0CdRLLG0CXN4yBdaUTdPL6zW++yDFfV d9morv+7a1pkXjkKZLGhg42leomEsG3yOY/LUvmeI7p74dvImpIdlZ+hVxW2bRPJa1 EnR+f8uCtq2nwqb4bowrT5fporOqCSIT2OWtiwOHYZKKevZ2sqcl0dhKRiXN/W1VTf T3JnjgarvGwRpiC+6sbx7CJfmMTNXMJbxZ+2eZvxX9FSc8qEYjP7BB1HwU+r3h1AXj QaDl1DJbAtFutxlyg3qP2d0PNjBvS5b6oUjoQZ0i0yJpmByBkdKGovCyF8vwNHNDEe YwpOXuN0+M/Ig== From: "David Hildenbrand (Arm)" To: linux-kernel@vger.kernel.org Cc: "linux-mm @ kvack . org" , "David Hildenbrand (Arm)" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , David Rientjes , Shakeel Butt , "Matthew Wilcox (Oracle)" , Alice Ryhl , Madhavan Srinivasan , Michael Ellerman , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Jarkko Sakkinen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Greg Kroah-Hartman , =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Todd Kjos , Christian Brauner , Carlos Llamas , Ian Abbott , H Hartley Sweeten , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Jason Gunthorpe , Leon Romanovsky , Dimitri Sivanich , Arnd Bergmann , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Andy Lutomirski , Vincenzo Frascino , Eric Dumazet , Neal Cardwell , "David S. Miller" , David Ahern , Jakub Kicinski , Paolo Abeni , Miguel Ojeda , linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-sgx@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, rust-for-linux@vger.kernel.org, x86@kernel.org Subject: [PATCH v1 09/16] mm/memory: convert details->even_cows into details->skip_cows Date: Fri, 27 Feb 2026 21:08:40 +0100 Message-ID: <20260227200848.114019-10-david@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260227200848.114019-1-david@kernel.org> References: <20260227200848.114019-1-david@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The current semantics are confusing: simply because someone specifies an empty zap_detail struct suddenly makes should_zap_cows() behave differently. The default should be to also zap CoW'ed anonymous pages. Really only unmap_mapping_pages() and friends want to skip zapping of these anon folios. So let's invert the meaning; turn the confusing "reclaim_pt" check that overrides other properties in should_zap_cows() into a safety check. Note that the only caller that sets reclaim_pt=true is madvise_dontneed_single_vma(), which wants to zap any pages. Signed-off-by: David Hildenbrand (Arm) --- include/linux/mm.h | 2 +- mm/madvise.c | 1 - mm/memory.c | 12 ++++++------ 3 files changed, 7 insertions(+), 8 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index d3ef586ee1c0..21b67c203e62 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2798,7 +2798,7 @@ extern void pagefault_out_of_memory(void); */ struct zap_details { struct folio *single_folio; /* Locked folio to be unmapped */ - bool even_cows; /* Zap COWed private pages too? */ + bool skip_cows; /* Do not zap COWed private pages */ bool reclaim_pt; /* Need reclaim page tables? */ zap_flags_t zap_flags; /* Extra flags for zapping */ }; diff --git a/mm/madvise.c b/mm/madvise.c index 557a360f7919..b51f216934f3 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -853,7 +853,6 @@ static long madvise_dontneed_single_vma(struct madvise_behavior *madv_behavior) struct madvise_behavior_range *range = &madv_behavior->range; struct zap_details details = { .reclaim_pt = true, - .even_cows = true, }; zap_page_range_single_batched( diff --git a/mm/memory.c b/mm/memory.c index fdcd2abf29c2..7d7c24c6917c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1554,11 +1554,13 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) static inline bool should_zap_cows(struct zap_details *details) { /* By default, zap all pages */ - if (!details || details->reclaim_pt) + if (!details) return true; + VM_WARN_ON_ONCE(details->skip_cows && details->reclaim_pt); + /* Or, we zap COWed pages only if the caller wants to */ - return details->even_cows; + return !details->skip_cows; } /* Decides whether we should zap this folio with the folio pointer specified */ @@ -2149,8 +2151,6 @@ void unmap_vmas(struct mmu_gather *tlb, struct unmap_desc *unmap) struct mmu_notifier_range range; struct zap_details details = { .zap_flags = ZAP_FLAG_DROP_MARKER | ZAP_FLAG_UNMAP, - /* Careful - we need to zap private pages too! */ - .even_cows = true, }; vma = unmap->first; @@ -4282,7 +4282,7 @@ void unmap_mapping_folio(struct folio *folio) first_index = folio->index; last_index = folio_next_index(folio) - 1; - details.even_cows = false; + details.skip_cows = true; details.single_folio = folio; details.zap_flags = ZAP_FLAG_DROP_MARKER; @@ -4312,7 +4312,7 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start, pgoff_t first_index = start; pgoff_t last_index = start + nr - 1; - details.even_cows = even_cows; + details.skip_cows = !even_cows; if (last_index < first_index) last_index = ULONG_MAX; -- 2.43.0