From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 9E42C1EBA05 for ; Mon, 11 Nov 2024 20:55:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731358515; cv=none; b=Z9NUlp62LFqkImJEnHDpWDwpRkG1Pmgux1lP0dYtfe8zt81FY4Ekg2A7poWolvLb/ebWeRwkRKi12zxnneWZCkCG5kZyHs36SrMhZsQFBK71jw3rV4/TfmtpxkANepBX8MPGAtKZvYUQG0CNDgnS6gTw6KHqhfGjdOa4DXio80o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731358515; c=relaxed/simple; bh=C8mwSaQ8Its/aWvWsxyeJgOzWgBQWhPS8Ji8jwToFzg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=f7MmPHQy2+WQwojX2l03kgGY70l54sAFOkQ4ic5OWmHUkwTvoCDiYwmIHLp7Yk8ICMX04it3NNNd59syvvqpeXFufppXMNQWYgQv9hInv+0E/9TCCZFXWjkWbfO3f/W0o63GXTEKW1CfILjyFuw+HI6v6ztIIPiMHYqteUkPscc= 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=Roi810DX; arc=none smtp.client-ip=209.85.219.202 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="Roi810DX" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e2971589916so7842872276.3 for ; Mon, 11 Nov 2024 12:55:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1731358512; x=1731963312; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=c6L2TsxMW3xdptYp+SxjhxiQb9Rn3imOm+Hs2oG6vZc=; b=Roi810DXtrY8vb58LPyGPngm13kyemggIfcBJzu7McA/b6bvgpq8uEckqfwGzvBtvb Si7LB2B7bxTjQYq253/eGRr9AdfzWNUTiotNOzhNeL8fh1fog9Gq0hGA3pP3ACbKQUJF +txc0DouLWBgHXwhLwc098OiRDmqLYubuVgRuxWdZNN2M+O03ylXC94QXVfN39sTyG9M nh56ffqokO7GKEYDsxi9TO/mLR4QOdowXiJ1puRLzkaPF/aLgMea9HC27zcTMQuDSRiv k2ag6N/DUD3J5JPTPLK8TJGF2eup18dhwGIFLDFScmAiqR0FwS+bLWGqpJyAgUFo4uOJ Gq7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1731358512; x=1731963312; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=c6L2TsxMW3xdptYp+SxjhxiQb9Rn3imOm+Hs2oG6vZc=; b=sANzXGlLORA+lBOIVLv4hrFwQku4sy6UYLaDgC9O7ZibOpENMgHFG6v537Kcm1z4Xf YfmSHz0oysXOGQBQJOVOM88O2FlIBDZbvGCe2tM1odghY4Xknd+l6W2QdfXQgD0FIhkh yezff3Tl1rN0gpUhYcU7Fcr6Aei9A5dex/OwZsMJDSBkybmdmgYLEPYOqnoeAeWvFynK jbUAUr+rhLRtnuzSXVtHD7Eaz++pdgMeXqqb7YnZdc3kKZCUXwse0X1xBINhpGHBkOyZ KParE2i1sa/gfyZvcKXbr8gXwJQ8uR+tXsGcHYFb5MsvZllaVA3sO2T/R4Au4P5aUzX0 g2LQ== X-Forwarded-Encrypted: i=1; AJvYcCW12dHDUbmt+mVZV/VyrnF62qUR9B7iRSFnlgCQA4j+ytMIumSNfAgLE/fZb/De65sgxRMjUEikZVOvaH0=@vger.kernel.org X-Gm-Message-State: AOJu0YzCIB60b8n9Az1TIClY2kAM3/qioHq9YPpTxy9t01TiEH/aZTQb 8vRHxzSQ26PmlNg39Ip3OnsHg9wm/G2yc/4tpU9IZZ8Se0oZ5VUQkNuM3PqgkBJWV2jjlCUDoX2 qHg== X-Google-Smtp-Source: AGHT+IFtRvBKCg21ZonSdl0i6oAaNOlWcK8osbIXD1VUy6Zm+UF4tEaZT/nKAdEJtdzHD4gxQkKcsjXP+Js= X-Received: from surenb-desktop.mtv.corp.google.com ([2a00:79e0:2e3f:8:53af:d9fa:522d:99b1]) (user=surenb job=sendgmr) by 2002:a25:af4b:0:b0:e33:104c:fac8 with SMTP id 3f1490d57ef6-e337f8d7427mr11316276.7.1731358512081; Mon, 11 Nov 2024 12:55:12 -0800 (PST) Date: Mon, 11 Nov 2024 12:55:03 -0800 In-Reply-To: <20241111205506.3404479-1-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241111205506.3404479-1-surenb@google.com> X-Mailer: git-send-email 2.47.0.277.g8800431eea-goog Message-ID: <20241111205506.3404479-2-surenb@google.com> Subject: [PATCH 1/4] mm: introduce vma_start_read_locked{_nested} helpers From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Type: text/plain; charset="UTF-8" Introduce helper functions which can be used to read-lock a VMA when holding mmap_lock for read. Replace direct accesses to vma->vm_lock with these new helpers. Signed-off-by: Suren Baghdasaryan --- include/linux/mm.h | 20 ++++++++++++++++++++ mm/userfaultfd.c | 14 ++++++-------- 2 files changed, 26 insertions(+), 8 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index fecd47239fa9..01ce619f3d17 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -722,6 +722,26 @@ static inline bool vma_start_read(struct vm_area_struct *vma) return true; } +/* + * Use only while holding mmap_read_lock which guarantees that nobody can lock + * the vma for write (vma_start_write()) from under us. + */ +static inline void vma_start_read_locked_nested(struct vm_area_struct *vma, int subclass) +{ + mmap_assert_locked(vma->vm_mm); + down_read_nested(&vma->vm_lock->lock, subclass); +} + +/* + * Use only while holding mmap_read_lock which guarantees that nobody can lock + * the vma for write (vma_start_write()) from under us. + */ +static inline void vma_start_read_locked(struct vm_area_struct *vma) +{ + mmap_assert_locked(vma->vm_mm); + down_read(&vma->vm_lock->lock); +} + static inline void vma_end_read(struct vm_area_struct *vma) { rcu_read_lock(); /* keeps vma alive till the end of up_read */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 60a0be33766f..55019c11b5a8 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -86,13 +86,11 @@ static struct vm_area_struct *uffd_lock_vma(struct mm_struct *mm, vma = find_vma_and_prepare_anon(mm, address); if (!IS_ERR(vma)) { /* + * While holding mmap_lock we can't fail * We cannot use vma_start_read() as it may fail due to - * false locked (see comment in vma_start_read()). We - * can avoid that by directly locking vm_lock under - * mmap_lock, which guarantees that nobody can lock the - * vma for write (vma_start_write()) under us. + * false locked (see comment in vma_start_read()). */ - down_read(&vma->vm_lock->lock); + vma_start_read_locked(vma); } mmap_read_unlock(mm); @@ -1480,10 +1478,10 @@ static int uffd_move_lock(struct mm_struct *mm, * See comment in uffd_lock_vma() as to why not using * vma_start_read() here. */ - down_read(&(*dst_vmap)->vm_lock->lock); + vma_start_read_locked(*dst_vmap); if (*dst_vmap != *src_vmap) - down_read_nested(&(*src_vmap)->vm_lock->lock, - SINGLE_DEPTH_NESTING); + vma_start_read_locked_nested(*src_vmap, + SINGLE_DEPTH_NESTING); } mmap_read_unlock(mm); return err; -- 2.47.0.277.g8800431eea-goog