From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1522285250; cv=none; d=google.com; s=arc-20160816; b=RXukR10WEbXrq/eqv7OU8KHiiXcL9hf+MZsTEpU84H/YAPFWTkXTqypFnoxP/AOg8k T0uR6+vt7kVg8kULyx39l2QpL3eNLtpt9fdf+Kp42R8N2AMYV5MwpzffEKXeArVUfZXv VI7LvtiKyprjkyWjOWd5ifq5Zp0ukF9g4KwfAqQC+FnK1LJuliAv9edNoNiPdrpj+z+y Nnz6uI0QE6LyNBxq8nd2GH1B5phJL9uIdHxLF19I5bPbz1e+o5WtyuVt576m3ntuYVPw JYEAOOgNhjhuVCJNKGtMlQ7Jv534/M/7bWy7xio8jdB7sBGIJNv9uyyz5F2RIjQgBSUX W6yQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:date:subject:cc:to:from:sender:dkim-signature :arc-authentication-results; bh=N2aURBRe0w1n4wUc4M3WZykN/13gESjGQGoIxDvr3y0=; b=k4P/c+J4jJdBx5Dj/FL07Q512a/UjaJotgdl4Tw3Z/+9r1rJq7few23GFxyUiv2Gta Z1a2AFZ1em9BiFf2O6ZNDW2TID49lVhzly27GTfHdVQVTS0sqwnJ9+hvtNIKkqL+LYov NISHrX5Oe8cQGSpVzhrChhFR3A/+tMnll0gKig4E2TPymF4imSDT6b2Z1e0L9mo1QpJm Y4h72wWXILexvJMBHgBkxQO4ONs1fc+GO0JYOnJADeLLMgQQvKF5xnszLZ2PccIe8BsU BAsGi3+y9iy5ohhoCVXhXgT8cMg7i7askEPtO05ds7JFBYvaFH6c/AOdlAz99+LhkO9m Y6HA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=OBB42fjx; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=OBB42fjx; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com X-Google-Smtp-Source: AIpwx48sFllERyWoZGQ8e5L0mM6Bo92MhrY2Viq0m7+1bUAkM9aSDWjDvcizWW/HC0T6zv3LoDGiCA== Sender: Minchan Kim From: Minchan Kim To: LKML Cc: Minchan Kim , Todd Kjos , Greg Kroah-Hartman , Martijn Coenen Subject: [PATCH v2] ANDROID: binder: change down_write to down_read Date: Thu, 29 Mar 2018 10:00:40 +0900 Message-Id: <20180329010040.96760-1-minchan@kernel.org> X-Mailer: git-send-email 2.17.0.rc1.321.gba9d0f2565-goog X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1596231778699320743?= X-GMAIL-MSGID: =?utf-8?q?1596231778699320743?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: binder_update_page_range needs down_write of mmap_sem because vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless it is set. However, when I profile binder working, it seems every binder buffers should be mapped in advance by binder_mmap. It means we could set VM_MIXEDMAP in bider_mmap time which is already hold a mmap_sem as down_write so binder_update_page_range doesn't need to hold a mmap_sem as down_write. Android suffers from mmap_sem contention so let's reduce mmap_sem down_write. Cc: Todd Kjos Cc: Greg Kroah-Hartman Reviewed-by: Martijn Coenen Signed-off-by: Minchan Kim --- >>From v1: * remove WARN_ON_ONCE - Greg * add reviewed-by - Martijn Martijn, I took your LGTM of v1 as Reviewed-by. If you don't like it or want to change it to acked-by, please, tell me. drivers/android/binder.c | 2 +- drivers/android/binder_alloc.c | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 764b63a5aade..9a14c6dd60c4 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -4722,7 +4722,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma) failure_string = "bad vm_flags"; goto err_bad_arg; } - vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE; + vma->vm_flags |= (VM_DONTCOPY | VM_MIXEDMAP) & ~VM_MAYWRITE; vma->vm_ops = &binder_vm_ops; vma->vm_private_data = proc; diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 5a426c877dfb..4f382d51def1 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -219,7 +219,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, mm = alloc->vma_vm_mm; if (mm) { - down_write(&mm->mmap_sem); + down_read(&mm->mmap_sem); vma = alloc->vma; } @@ -288,7 +288,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, /* vm_insert_page does not seem to increment the refcount */ } if (mm) { - up_write(&mm->mmap_sem); + up_read(&mm->mmap_sem); mmput(mm); } return 0; @@ -321,7 +321,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, } err_no_vma: if (mm) { - up_write(&mm->mmap_sem); + up_read(&mm->mmap_sem); mmput(mm); } return vma ? -ENOMEM : -ESRCH; -- 2.17.0.rc1.321.gba9d0f2565-goog