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 8882E47F58; Mon, 22 Jan 2024 15:04:21 +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=1705935861; cv=none; b=qV5nyI6OGiMSa30AihQmApjYI5bLZFVYRlA4mEMf2iXD6jck+toE4G6Xvh7ZEWKo9f35isMetZbpje2ot0uSIdbPeTkSBzMre6kovfFOSAf1vY1Z/tmKnd2Wn5N4JFeiwZTZlJ0xxZHG/XV8SaSA866dRg/KvkjNbCpYiLwms6U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705935861; c=relaxed/simple; bh=HJlEOLIuCq3sg9A8tPi7mwWYHioo2FNzf0m9QyRk4JA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sKBEDLsZAeNQsrfLta1tYQvPsIo+bBtY6l8r76UWui4wry+PXWV205nSHyTf6CFVX/3Bp028NB6ExIlGIcnFAIZ6w3Mll4nPGCITHLu7Q0RGu5NSjgYbpoShY4W3fBtVUtcHC2aGk/UFygqkEgXAhR3GZiDHFdvOg8AYiUCxfcA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sL2CU03v; 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="sL2CU03v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FAD6C433A6; Mon, 22 Jan 2024 15:04:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1705935861; bh=HJlEOLIuCq3sg9A8tPi7mwWYHioo2FNzf0m9QyRk4JA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sL2CU03vncHGeY/4nlUEjrgxefE//nw1bbgBD+5Jb24IZwrs8XhhJpbAgolZhpbUu mKG1hfVhauLMDqxg7fugLXzyI0jDdWPAcUbJRIv7KMbbff0v6EZon4eqFf5WNM26lb 7oY1VPbv2QbRiU4nHAxlNt1NRcCvd4pDoTkzKxVA= Date: Mon, 22 Jan 2024 07:04:20 -0800 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: <2024012203-expedited-job-1d79@gregkh> References: <20231201172212.1813387-1-cmllamas@google.com> <20231201172212.1813387-6-cmllamas@google.com> <2024011955-quotation-zone-7f20@gregkh> Precedence: bulk X-Mailing-List: stable@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 Fri, Jan 19, 2024 at 05:27:18PM +0000, Carlos Llamas wrote: > On Fri, Jan 19, 2024 at 06:49:00AM +0100, Greg Kroah-Hartman wrote: > > 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. > > > > > > Oops, here is the complete info: > > Commit ID: c6d05e0762ab276102246d24affd1e116a46aa0c > Subject: "binder: fix unused alloc->free_async_space" > Reason: Fixes an incorrect calculation of available space. > Versions: v4.19+ > > Note this patch will also have trivial conflicts in v4.19 and v5.4 > kernels as commit 261e7818f06e is missing there. Please let me know and > I can send the corresponding patches separately. It doesn't even apply to 6.7.y either, so we need backports for all affected trees, thanks. greg k-h