From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH net-next v4] xen-netback: Adding debugfs "io_ring_qX" files Date: Mon, 11 Aug 2014 11:50:56 +0100 Message-ID: <53E8A010.1080208@citrix.com> References: <20140811103802.GA3249@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140811103802.GA3249@zion.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Wei Liu , SeeChen Ng Cc: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 11/08/14 11:38, Wei Liu wrote: > On Sun, Aug 10, 2014 at 10:57:51PM +0800, SeeChen Ng wrote: >> Hi, I'm a noob to linux kernel, I tried to figure out the usage of the function >> "simple_write_to_buffer", and I got confused about the code here. >> >>> +static ssize_t >>> +xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count, >>> + loff_t *ppos) >>> +{ >>> + struct xenvif_queue *queue = >>> + ((struct seq_file *)filp->private_data)->private; >>> + int len; >>> + char write[sizeof(XENVIF_KICK_STR)]; >>> + >>> + /* don't allow partial writes and check the length */ >>> + if (*ppos != 0) >>> + return 0; >>> + if (count < sizeof(XENVIF_KICK_STR) - 1) >>> + return -ENOSPC; >> The statement here is trying to verify the value of "count" is smaller >> than the size of array "write", make sure that the array got >> enough space for the write operation, right? >> > > Yes I think so. Is anyone reading the comment? /* don't allow partial writes and check the length */ The sense of the check is correct. David