From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f71.google.com (mail-pj1-f71.google.com [209.85.216.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 465C142123B for ; Thu, 13 Aug 2026 19:34:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786649681; cv=none; b=a9WvhgYWtXEmpHLDGX1zEaO4GlJPFLYelxzkOImDfhTin5+xkCWU//fc1iectfhG5kmfqBLkWzoU8VChXFePwmZ5kcrDcGxf7kZnra3+SFWSYrHOJ8m34tH+65g4eEe0Nn5D6E7wE+Ni2WviROccgyONaBZE/Okfa2PWxT1HVWA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786649681; c=relaxed/simple; bh=pszYivCzPET0xa1JnP+lRORaPl+hKmdl+WtEK02wUN0=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=ITu4+cFFLo9n7Bzdq5A7bTcuP4Kl//h1ZV1+TvU7cA6HdeNwyV3jfujVHEh5bY/hJWBhHhdQf9RIcsw0z/vw30lN1lTyaJqyRGMyLJdRb6AfacsYQwWCQwI3nNcy46eSicI97ADaMP8hL6kmHKfaSkPDXcrbOcILGJgmJ9e0wAo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=SVnf3Clo; arc=none smtp.client-ip=209.85.216.71 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="SVnf3Clo" Received: by mail-pj1-f71.google.com with SMTP id 98e67ed59e1d1-392cf18db8eso280022a91.3 for ; Thu, 13 Aug 2026 12:34:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786649678; x=1787254478; darn=vger.kernel.org; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:mime-version:date:from:to:cc:subject:date:message-id :reply-to:content-type; bh=myMALrPmiftJzuMGzKXuNexYM0KxETCacC1JofGVCac=; b=SVnf3CloULQ2tLCJ8A+kZdAFFJltHG/NTaSGIEmSvCd9M5spKK3aKXlbnRBPRwggG7 s6Z1eB8ll1uo7kto2Uj54+NjOmStMBcXZUuXDuyeRSMLM9CztUzbW6gnHGj1gzJp/GUg IAou4BPjTQ9142zr1aUsd8HzyuNQYUe9E+LfDrm2VzW6t0df9t7gso5exyuV973iintN W1xQgbQ1G9ct+NBi1iiKKPJ1+iL2imN95sn55kbOVj/yulk11Q01wG4X/QLuJCD1+iZs Knt5+VjBrszH3G5rh1rwtEWP+5uravMzgpX3hcilbPXy1iXRuHGepoLNWYHm6Sxle0J9 JVuA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786649678; x=1787254478; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:mime-version:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to:content-type; bh=myMALrPmiftJzuMGzKXuNexYM0KxETCacC1JofGVCac=; b=Y5Whs6v8IKHhdmpOe9/QkElj6wh8/5wvQPau1ncdZGweszixBnBPaU+u3cNacrQldR lDfU3V2Ki0F4W+wzu22aEQkee9Yepp/tNZ4+S6mZWy3ZYTEG1iDjX59BDW8j/P4xtOy7 D/6q2y7IKdyhqQO8mEL9eKE/3s6qJ9UBE9bV9zfT/eR64Kanf+cxBHVyC0M9BTZaLSIG 6tleB+mukde3mNTwLprKPMdw/KSoa9NkucrYkCXwfhwGxiOvdqS0T6v97PH/M09zle29 vVPtRnXdRZZNSjUn9Hhnbk1IAVw2j85FS4aXdUeFEQv/dlmANXe1kXViQ/diOxnE94sK i+8w== X-Forwarded-Encrypted: i=1; AHgh+RqNRUu12fTZbeY3/Va+O/W01wVMT4NiIdaRxwL6R513EfYVC4C5//BviHm9vZNGqpy7mTgiry1vl5VIstE=@vger.kernel.org X-Gm-Message-State: AOJu0Yx8LpUmmjqLP9RXcHms+QMoD5u5/Xgb4bb80mPpX4NdcR2U8Tkq pRW6TIFt41W3SwzEuDvrDQwSgMYKKSg5Z1dt0zK2yuPSzOc/DMbtDU9Kv2NLWm0zSnpHgsh1ZJS RMQsdtA== X-Received: from dybvt10.prod.google.com ([2002:a05:7301:78ca:b0:313:d014:d248]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:4b90:b0:37f:e177:f58 with SMTP id 98e67ed59e1d1-3933b874ba2mr305120a91.9.1786649677316; Thu, 13 Aug 2026 12:34:37 -0700 (PDT) Date: Thu, 13 Aug 2026 12:34:28 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.691.gc56d675ccc-goog Message-ID: <20260813193433.3318288-1-surenb@google.com> Subject: [PATCH v6 0/5] mm: Unconditional per-VMA locks and cleanups From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: dave.hansen@linux.intel.com, Liam.Howlett@oracle.com, ljs@kernel.org, david@redhat.com, willy@infradead.org, shakeel.butt@linux.dev, vbabka@kernel.org, jannh@google.com, aliceryhl@google.com, arve@android.com, cmllamas@google.com, christian@brauner.io, tkjos@android.com, dsahern@kernel.org, davem@davemloft.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, surenb@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable v2 version of this patchset [1] was written by Dave Hansen and per his request, I'm taking over this series. tl;dr: Make per-VMA locks available in all configs. Simplify some of the per-VMA lock users now that they can rely on them being always available. Binder and networking folks: Your code is the target of the cleanups. I'm cc'ing you now on v2 because there's emerging consensus on the mm side that the approach here is sane. I'm not quite sure how this pile would get merged, but ack/review tags would be appreciated if this looks good to you. Longer version: When working on some x86 shadow stack code, it was a real pain to avoid causing recursive locking problems with mmap_lock. One way to avoid those was to avoid mmap_lock and use per-VMA locks instead. They are great, but they are not available in all configs which makes them unusable in generic code, or if you want to completely avoid mmap_lock. Make per-VMA locks available in all configs. Right now, they are only available on select architectures when SMP and MMU are enabled. But all of the primitives that per-VMA locks are built on (RCU, maple trees, refcounts) work just fine without SMP or MMU. The only real downside is that making VMAs a wee bit bigger on !MMU and !SMP builds. The upside is much cleaner code, lower complexity and less #ifdeffery. Clean up a binder VMA locking site now that it can rely on per-VMA locks. Building on top of universally-available per-VMA locks, introduce a new helper. Since the new API does not require callers to have a fallback to mmap_lock, it's much easier to use. Callers can potentially replace this very common kernel idiom: mmap_read_lock(mm); vma =3D vma_lookup() // fiddle with vma mmap_read_unlock(mm); with: vma =3D vma_start_read_unlocked(mm, address); // fiddle with vma vma_end_read(vma); Which avoids mmap_lock entirely in the fast path. Use that new API for another binder site and one in the TCP code. Cc: Suren Baghdasaryan Cc: Andrew Morton Cc: "Liam R. Howlett" Cc: Lorenzo Stoakes Cc: Vlastimil Babka Cc: Jann Horn Cc: Shakeel Butt Cc: linux-mm@kvack.org Cc: Greg Kroah-Hartman Cc: Arve Hj=C3=B8nnev=C3=A5g Cc: Todd Kjos Cc: Christian Brauner Cc: Carlos Llamas Cc: Alice Ryhl Cc: "David S. Miller" Cc: David Ahern Cc: netdev@vger.kernel.org Changes since v5 [2]: Patch 2: - Removed dead code, per Alice Ryhl - Rebased over mm-unstable Applies cleanly over mm-unstable [1] https://lore.kernel.org/all/20260610230409.A44D29FA@davehans-spike.ostc= .intel.com/ [2] https://lore.kernel.org/all/20260812011056.902771-1-surenb@google.com/ Dave Hansen (5): mm: Make per-VMA locks available universally binder: Make shrinker rely solely on per-VMA lock mm: Add RCU-based VMA lookup helper that waits for writers binder: Remove mmap_lock fallback tcp: Remove mmap_lock fallback path arch/arm/Kconfig | 1 - arch/arm64/Kconfig | 1 - arch/loongarch/Kconfig | 1 - arch/powerpc/platforms/powernv/Kconfig | 1 - arch/powerpc/platforms/pseries/Kconfig | 1 - arch/riscv/Kconfig | 1 - arch/s390/Kconfig | 1 - arch/x86/Kconfig | 2 - drivers/android/binder/page_range.rs | 19 +----- drivers/android/binder_alloc.c | 63 +++++++---------- fs/proc/internal.h | 2 - fs/proc/task_mmu.c | 93 ------------------------- include/linux/mm.h | 12 ---- include/linux/mm_types.h | 8 +-- include/linux/mmap_lock.h | 94 +++++++++++--------------- kernel/bpf/stackmap.c | 17 ++--- kernel/bpf/task_iter.c | 2 +- kernel/fork.c | 2 - mm/Kconfig | 12 ---- mm/Kconfig.debug | 1 - mm/debug.c | 4 -- mm/init-mm.c | 2 - mm/memory.c | 2 - mm/mmap_lock.c | 61 ++++++++++------- mm/pagewalk.c | 2 - mm/rmap.c | 2 - mm/userfaultfd.c | 61 ++--------------- net/ipv4/tcp.c | 31 +++------ rust/kernel/mm.rs | 57 ++++++++++------ tools/testing/vma/include/dup.h | 5 +- tools/testing/vma/vma_internal.h | 1 - 31 files changed, 166 insertions(+), 396 deletions(-) base-commit: f9ca2fa9ef7e9b39ec79a0596929d1a1f8704c5f --=20 2.55.0.691.gc56d675ccc-goog