From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7EF46D29E; Fri, 19 Jan 2024 05:49:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705643343; cv=none; b=ovuwlWHk8+yMney6DGo6+nIHMJVXVFxnnoQLgwHv7bpYuik+W+7ZHX25FdXJ4e2RsqfIF8wHzOuFiFaoJhBbqjk1R425L+R622SQcfF3GmezLWhyQSPbxVy/izmSzXlaf1s5f41sIgj8wS3jfHbLuN+bLtuEQssN8WdAf6ergRA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705643343; c=relaxed/simple; bh=givEckCEBG994/AoJcSh11hoPD5I6LKxZjQVj1cedyw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=R6hMnrHN4fVTMj1oDxoytmc+DMPGpxQyuNj0QmroBDfbAE3lJTRjU/iCn9fljBULeUxo9dq/JBt9GfKWBYb+GtOpwnVBo5Rp1PngV5ASOk0HOHuo0mLUnoNLemS8pkILphZi6o7mQa82nSyrwwBF17yfiq3BVaMv82x31SPJuYM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0GccOKXT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="0GccOKXT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AEC55C433C7; Fri, 19 Jan 2024 05:49:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1705643343; bh=givEckCEBG994/AoJcSh11hoPD5I6LKxZjQVj1cedyw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=0GccOKXTJNo5k3sUULxAkCSnqL7koN8n4sFY26qMlD22SfTELKp8Sr03ZVUASTn8c VpmF2JBLcdY6ZfP1wcHsBkzkxz2Q5LKxzl9rN7H7I1Wjt76RKZlj+WF0bcr7NMUuFg L6HQDgSOMMbRXGftgGMHGmHi5n2kUEm1i+4NqIv8= Date: Fri, 19 Jan 2024 06:49:00 +0100 From: Greg Kroah-Hartman To: Carlos Llamas Cc: Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Todd Kjos , Martijn Coenen , Joel Fernandes , Christian Brauner , Suren Baghdasaryan , Sherry Yang , linux-kernel@vger.kernel.org, kernel-team@android.com, stable@vger.kernel.org Subject: Re: [PATCH v2 05/28] binder: fix unused alloc->free_async_space Message-ID: <2024011955-quotation-zone-7f20@gregkh> References: <20231201172212.1813387-1-cmllamas@google.com> <20231201172212.1813387-6-cmllamas@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jan 18, 2024 at 07:33:48PM +0000, Carlos Llamas wrote: > On Fri, Dec 01, 2023 at 05:21:34PM +0000, Carlos Llamas wrote: > > Each transaction is associated with a 'struct binder_buffer' that stores > > the metadata about its buffer area. Since commit 74310e06be4d ("android: > > binder: Move buffer out of area shared with user space") this struct is > > no longer embedded within the buffer itself but is instead allocated on > > the heap to prevent userspace access to this driver-exclusive info. > > > > Unfortunately, the space of this struct is still being accounted for in > > the total buffer size calculation, specifically for async transactions. > > This results in an additional 104 bytes added to every async buffer > > request, and this area is never used. > > > > This wasted space can be substantial. If we consider the maximum mmap > > buffer space of SZ_4M, the driver will reserve half of it for async > > transactions, or 0x200000. This area should, in theory, accommodate up > > to 262,144 buffers of the minimum 8-byte size. However, after adding > > the extra 'sizeof(struct binder_buffer)', the total number of buffers > > drops to only 18,724, which is a sad 7.14% of the actual capacity. > > > > This patch fixes the buffer size calculation to enable the utilization > > of the entire async buffer space. This is expected to reduce the number > > of -ENOSPC errors that are seen on the field. > > > > Fixes: 74310e06be4d ("android: binder: Move buffer out of area shared with user space") > > Signed-off-by: Carlos Llamas > > --- > > Sorry, I forgot to Cc: stable@vger.kernel.org. This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.