From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx133.postini.com [74.125.245.133]) by kanga.kvack.org (Postfix) with SMTP id EBF8D6B006C for ; Sun, 28 Oct 2012 21:16:36 -0400 (EDT) Date: Mon, 29 Oct 2012 12:16:32 +1100 From: Dave Chinner Subject: Re: [PATCH 2/3] ext4: introduce ext4_error_remove_page Message-ID: <20121029011632.GN29378@dastard> References: <1351177969-893-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1351177969-893-3-git-send-email-n-horiguchi@ah.jp.nec.com> <20121026061206.GA31139@thunk.org> <3908561D78D1C84285E8C5FCA982C28F19D5A13B@ORSMSX108.amr.corp.intel.com> <20121026184649.GA8614@thunk.org> <3908561D78D1C84285E8C5FCA982C28F19D5A388@ORSMSX108.amr.corp.intel.com> <20121027221626.GA9161@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121027221626.GA9161@thunk.org> Sender: owner-linux-mm@kvack.org List-ID: To: Theodore Ts'o , "Luck, Tony" , Naoya Horiguchi , "Kleen, Andi" , "Wu, Fengguang" , Andrew Morton , Jan Kara , Jun'ichi Nomura , Akira Fujita , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-ext4@vger.kernel.org" On Sat, Oct 27, 2012 at 06:16:26PM -0400, Theodore Ts'o wrote: > On Fri, Oct 26, 2012 at 10:24:23PM +0000, Luck, Tony wrote: > > > Well, we could set a new attribute bit on the file which indicates > > > that the file has been corrupted, and this could cause any attempts to > > > open the file to return some error until the bit has been cleared. > > > > That sounds a lot better than renaming/moving the file. > > What I would recommend is adding a > > #define FS_CORRUPTED_FL 0x01000000 /* File is corrupted */ > > ... and which could be accessed and cleared via the lsattr and chattr > programs. Except that there are filesystems that cannot implement such flags, or require on-disk format changes to add more of those flags. This is most definitely not a filesystem specific behaviour, so any sort of VFS level per-file state needs to be kept in xattrs, not special flags. Filesystems are welcome to optimise the storage of such special xattrs (e.g. down to a single boolean flag in an inode), but using a flag for something that dould, in fact, storage the exactly offset and length of the corruption is far better than just storing a "something is corrupted in this file" bit.... > > > Application programs could also get very confused when any attempt to > > > open or read from a file suddenly returned some new error code (EIO, > > > or should we designate a new errno code for this purpose, so there is > > > a better indication of what the heck was going on?) > > > > EIO sounds wrong ... but it is perhaps the best of the existing codes. Adding > > a new one is also challenging too. > > I think we really need a different error code from EIO; it's already > horribly overloaded already, and if this is new behavior when the > customers get confused and call up the distribution help desk, they > won't thank us if we further overload EIO. This is abusing one of the > System V stream errno's, but no one else is using it: > > #define EADV 68 /* Advertise error */ > > I note that we've already added a new error code: > > #define EHWPOISON 133 /* Memory page has hardware error */ > > ... although the glibc shipping with Debian testing hasn't been taught > what it is, so strerror(EHWPOISON) returns "Unknown error 133". We > could simply allow open(2) and stat(2) return this error, although I > wonder if we're just better off defining a new error code. If we are going to add special new "file corrupted" errors, we should add EFSCORRUPTED (i.e. "filesystem corrupted") at the same time.... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org