Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756943AbZFMSwd (ORCPT ); Sat, 13 Jun 2009 14:52:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751565AbZFMSwZ (ORCPT ); Sat, 13 Jun 2009 14:52:25 -0400 Received: from waste.org ([66.93.16.53]:50542 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751013AbZFMSwY (ORCPT ); Sat, 13 Jun 2009 14:52:24 -0400 Subject: Re: [PATCH] ramfs: ignore tmpfs options when we emulate it From: Matt Mackall To: Hugh Dickins Cc: Mike Frysinger , Andrew Morton , Wu Fengguang , linux-kernel@vger.kernel.org In-Reply-To: References: <1244872920-13511-1-git-send-email-vapier@gentoo.org> Content-Type: text/plain Date: Sat, 13 Jun 2009 13:51:25 -0500 Message-Id: <1244919085.4496.192.camel@calx> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4346 Lines: 110 On Sat, 2009-06-13 at 15:15 +0100, Hugh Dickins wrote: > On Sat, 13 Jun 2009, Mike Frysinger wrote: > > > On systems where CONFIG_SHMEM is disabled, mounting tmpfs filesystems can > > fail when tmpfs options are used. This is because tmpfs creates a small > > wrapper around ramfs which rejects unknown options, and ramfs itself only > > supports a tiny subset of what tmpfs supports. This makes it pretty hard > > to use the same userspace systems across different configuration systems. > > As such, ramfs should ignore the tmpfs options when tmpfs is merely a > > wrapper around ramfs. > > Yes, indeed, thanks a lot for reporting this. > > But I'm uneasy with making ramfs behaviour differ with CONFIG_SHMEM > (perhaps that's silly: certainly tmpfs behaviour differs with it), > and uneasy with coding a list of options we need to remember to keep > in synch with mm/shmem.c. It's easier to justify ignoring all options, > than rejecting some while ignoring others yet not respecting them. > > > > > This used to work before commit c3b1b1cbf0 as previously, ramfs would > > ignore all options. But now, we get: > > ramfs: bad mount option: size=10M > > mount: mounting mdev on /dev failed: Invalid argument > > I rather think the correct response to bugzilla #12843 should have > been to say, either use chmod 1777 yourself, or use CONFIG_SHMEM=y. > I fear we'll now get a line of requests for support of uid, gid, ... > in ramfs; whereas ramfs is about blind simplicity, not feature bloat. > However, that mode= feature is now in, so I guess we ride with it. Ugh, hadn't noticed that go by. > > > > Signed-off-by: Mike Frysinger > > --- > > another option might be to restore the previous behavior where ramfs simply > > ignored all unknown mount options ... > > Yes, that would be my preference, return to the blind simplicity, with > that one exception for mode=. Alternative patch suggested at the bottom, > let's see if Cc's added feel strongly about it one way or another. > Thanks, > Hugh > > > > > fs/ramfs/inode.c | 10 ++++++++++ > > 1 files changed, 10 insertions(+), 0 deletions(-) > > > > diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c > > index 3a6b193..57a797c 100644 > > --- a/fs/ramfs/inode.c > > +++ b/fs/ramfs/inode.c > > @@ -203,6 +203,16 @@ static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) > > opts->mode = option & S_IALLUGO; > > break; > > default: > > +#ifndef CONFIG_SHMEM > > + /* If tmpfs is using us to emulate it, ignore its options */ > > + if (!strncmp(p, "gid=", 4) || > > + !strncmp(p, "mpol=", 5) || > > + !strncmp(p, "nr_blocks=", 10) || > > + !strncmp(p, "nr_inodes=", 10) || > > + !strncmp(p, "size=", 5) || > > + !strncmp(p, "uid=", 4)) > > + continue; > > +#endif > > printk(KERN_ERR "ramfs: bad mount option: %s\n", p); > > return -EINVAL; > > } > > -- > > 1.6.3.1 > > [PATCH] ramfs: ignore unknown mount options > > From: Mike Frysinger > > On systems where CONFIG_SHMEM is disabled, mounting tmpfs filesystems can > fail when tmpfs options are used. This is because tmpfs creates a small > wrapper around ramfs which rejects unknown options, and ramfs itself only > supports a tiny subset of what tmpfs supports. This makes it pretty hard > to use the same userspace systems across different configuration systems. > As such, ramfs should ignore the tmpfs options when tmpfs is merely a > wrapper around ramfs. > > This used to work before commit c3b1b1cbf0 as previously, ramfs would > ignore all options. But now, we get: > ramfs: bad mount option: size=10M > mount: mounting mdev on /dev failed: Invalid argument > > Another option might be to restore the previous behavior, where ramfs > simply ignored all unknown mount options ... which is what Hugh prefers. > > Signed-off-by: Mike Frysinger > Signed-off-by: Hugh Dickins Acked-by: Matt Mackall -- http://selenic.com : development and support for Mercurial and Linux -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/