From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1522306472; cv=none; d=google.com; s=arc-20160816; b=pIEr9VrsP73Cc+if2d1+Nr1zqdUnxTvBKK6S1yxJ6ZbjKTqUbJw91B1ehTWM9W3HHH 3Orzr7YJve0X/K9Nfpt0uzOzFDT5B0cy1NbUNJ27IKfLmfrv/K/aTMpcIgvp4DArP2Zf S8ebT5G7lC0SEv0pkseAudx10+11VzGPZosNyfb8sWYYczq+0E/XothCZ6WrJxKY+mz5 ZkYRopVGc4dMdQPApq3NQ6W2z8hBlfVBYsPZpvanwtS+hNsbYxeIvcU72TvUjMVMZg8z NU+5mObeoAlKtUUelVBskRi2PykltHnCpkhnu5EOcYB29Udk+0cGDcM6nJ0pJYC+yy0C jupw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:sender:dkim-signature:arc-authentication-results; bh=z0Ci4/IBlR4xy1mmF5s5NpANnuryDcpKb9nfeso5yDc=; b=HMyGf0InF+wlX+EcxZXuhYKfsChPcf8y2M1W1hkBDZxipd2pfHVspVPt2EsHxb05e6 wO2xjRtPDYFPDWotmuRmT1AOMttydPIXejWzCvNVwTZ7GCGc3gMdzrzLXKakjwhM+PNk a/Br0qj8ZWBHKVGwyPQhTC8l4Iac2evBIlvYU8ooqxoQ2l3mc6NKux/Lcbs//9yBSpWY omXAVk9drabNlxyxTiOUnDqZeX0qIn6D4R4uxYb2BVSLBu25T0r7kqCH22hKBtyrRirt 5ZYC7zptb4CxRr5Hy8cjIBWbel6wu/PAOc0jzZ9X2a+oZq9/0lbjjxPiTmj00Oe92wYq k7OQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=CD2gTQpE; 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=CD2gTQpE; 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: AIpwx4/Ndd6ipuAj8bO4itintszink3l7oTbqfHgF5IMdqprzirmclMZtuNBxClGtICqq8DKIoCexg== Sender: Minchan Kim From: Minchan Kim To: LKML Cc: Minchan Kim , Joe Perches , =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Todd Kjos , Greg Kroah-Hartman , Martijn Coenen Subject: [PATCH v5] ANDROID: binder: change down_write to down_read Date: Thu, 29 Mar 2018 15:54:24 +0900 Message-Id: <20180329065424.203172-1-minchan@kernel.org> X-Mailer: git-send-email 2.17.0.rc1.321.gba9d0f2565-goog MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1596254032587353794?= X-GMAIL-MSGID: =?utf-8?q?1596254032587353794?= 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 binder_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: Joe Perches Cc: Arve Hjønnevåg Cc: Todd Kjos Cc: Greg Kroah-Hartman Reviewed-by: Martijn Coenen Signed-off-by: Minchan Kim --- >>From v4: * Fix typo and VM flags clear handling - Joe >>From v3: * Fix typo >>From v2: * Fix vma->flag setting - Arve >>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 | 4 +++- drivers/android/binder_alloc.c | 6 +++--- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 764b63a5aade..bb63e3b54e0c 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -4722,7 +4722,9 @@ 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; + vma->vm_flags &= ~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