From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752995AbYKCSO2 (ORCPT ); Mon, 3 Nov 2008 13:14:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751279AbYKCSOT (ORCPT ); Mon, 3 Nov 2008 13:14:19 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:52801 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750932AbYKCSOT (ORCPT ); Mon, 3 Nov 2008 13:14:19 -0500 Date: Mon, 3 Nov 2008 10:14:16 -0800 (PST) From: Linus Torvalds To: Alexey Dobriyan , Al Viro cc: Linux Kernel Mailing List Subject: Re: [GIT] /proc/uptime fix In-Reply-To: <20081103145023.GA3986@x200.localdomain> Message-ID: References: <20081103145023.GA3986@x200.localdomain> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 3 Nov 2008, Alexey Dobriyan wrote: > > Alexey Dobriyan (1): > proc: revert /proc/uptime to ->read_proc hook Ok, pulled, but it's a bit sad. Al: the commit is 6c87df37dcb9c6c33923707fa5191e0a65874d60, and the message explains it all: Turned out some VMware userspace does pread(2) on /proc/uptime, but seqfiles currently don't allow pread() resulting in -ESPIPE. Seqfiles in theory can do pread(), but this can be a long story, so revert to ->read_proc until then. and I bet that the pread() usage is just with a constant loff_t of 0, and just there to avoid a simple case of "lseek+read". I wonder how hard it is to make seqfiles support pread. Maybe it's something as trivial as just flushing the buffer whenever 'pos' doesn't match f_pos? ie something like the following (TOTALLY UNTESTED!) I may be way off base here, Al needs to whack some sense into this. Linus --- fs/seq_file.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index eba2eab..eb95ec9 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -48,8 +48,8 @@ int seq_open(struct file *file, const struct seq_operations *op) */ file->f_version = 0; - /* SEQ files support lseek, but not pread/pwrite */ - file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE); + /* SEQ files support lseek, but not pwrite */ + file->f_mode &= ~(FMODE_PWRITE); return 0; } EXPORT_SYMBOL(seq_open); @@ -91,6 +91,8 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) if (!m->buf) goto Enomem; } + if (pos != file->f_pos) + m->count = 0; /* if not empty - flush it first */ if (m->count) { n = min(m->count, size); @@ -175,6 +177,8 @@ Done: else *ppos += copied; file->f_version = m->version; + if (pos != file->f_pos) + m->count = 0; mutex_unlock(&m->lock); return copied; Enomem: