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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 13A751C0007 X-Stat-Signature: xzqsybbwoto41atfrse15srzaqn69tw9 X-HE-Tag: 1772223098-981448 X-HE-Meta: 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 IuC5CUKp zKo5eqfOEGmX53puHc5RM0C5Oz/oTRyXGmYMOt4HjmOGPUHnjZuhPBNhL5Mloiflq5Th386Y252fBucqEIQ/miQZNJNbGSX+llojXgRLX02GMro/Pzit4HuHpX7vTy0KYavy0X72JWJg441LO9J7x2K6ibJO+mXcd4geqJ5BO12KqHoaej9+AGhr3nRU5MdYxydYuQStUED2jUzoAVZekmaoCkcEow2MdGauWbs5qXCCuSOnfWlszPPuqbmxhRH1wmkRve3qt4Z/KILuC6a7iU1zrOKf1GNejTeKf6z7GybmPnej3qT5sewllxhA+bJVcDv0q Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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