Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752928AbZDLUEd (ORCPT ); Sun, 12 Apr 2009 16:04:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752589AbZDLUEW (ORCPT ); Sun, 12 Apr 2009 16:04:22 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:35002 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751277AbZDLUEU (ORCPT ); Sun, 12 Apr 2009 16:04:20 -0400 To: Jamie Lokier Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Al Viro , Hugh Dickins , Tejun Heo , Alexey Dobriyan , Linus Torvalds , Alan Cox , Greg Kroah-Hartman References: <20090412185659.GE4394@shareable.org> From: ebiederm@xmission.com (Eric W. Biederman) Date: Sun, 12 Apr 2009 13:04:09 -0700 In-Reply-To: <20090412185659.GE4394@shareable.org> (Jamie Lokier's message of "Sun\, 12 Apr 2009 19\:56\:59 +0100") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in01.mta.xmission.com;;;ip=67.169.126.145;;;frm=ebiederm@xmission.com;;;spf=neutral X-SA-Exim-Connect-IP: 67.169.126.145 X-SA-Exim-Rcpt-To: jamie@shareable.org, gregkh@suse.de, alan@lxorguk.ukuu.org.uk, torvalds@linux-foundation.org, adobriyan@gmail.com, tj@kernel.org, hugh@veritas.com, viro@ZenIV.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa02 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Jamie Lokier X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa02 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 XM_SPF_Neutral SPF-Neutral * 0.4 UNTRUSTED_Relay Comes from a non-trusted relay Subject: Re: [RFC][PATCH 8/9] vfs: Implement generic revoked file operations X-SA-Exim-Version: 4.2.1 (built Thu, 25 Oct 2007 00:26:12 +0000) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1256 Lines: 30 Jamie Lokier writes: >> revoked_file_ops return 0 from reads (aka EOF). Tell poll the file is >> always ready for I/O and return -EIO from all other operations. > > I think read should return -EIO too. If a program is reading from a > /proc file (say), and the thing it's reading suddenly disappears, EOF > gives the false impression that it's read to the end of formatted data > from that file and it can process the data as if it's complete, which > is wrong. Good point EIO is the current read return value for a removed proc file. For closed pipes, and hung up ttys the read return value is 0, and from my reading that is what bsd returns after a sys_revoke. The reason I have f_op settable is because I never expected complete agreement on the return codes, and because it makes auditing and spotting this kind of thing easier. I guess I should make two variations on revoked_file_ops then. Say eof_file_ops, eio_file_ops. Identical except for their treatment of reads. Eric -- 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/