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Re: [RFD] FS behavior (I/O failure) in kernel summit

To: Jeff Mahoney <jeffm@xxxxxxxx>
Subject: Re: [RFD] FS behavior (I/O failure) in kernel summit
From: Dave Chinner <dgc@xxxxxxx>
Date: Thu, 16 Jun 2005 12:18:22 +1000
Cc: Hans Reiser <reiser@xxxxxxxxxxx>, fs <fs@xxxxxxxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxx>, Andrew Morton <akpm@xxxxxxxx>, viro VFS <viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>, linux-fsdevel <linux-fsdevel@xxxxxxxxxxxxxxx>, linux-kernel <linux-kernel@xxxxxxxxxxxxxxx>, zhiming@xxxxxxxxxxxxxxxxx, qufuping@xxxxxxxxxxxxxxxxxx, madsys@xxxxxxxxxxxxxxxxxx, xuh@xxxxxxxxxxxxxx, koichi@xxxxxxxxxxxxxxxxx, kuroiwaj@xxxxxxxxxxxxxxxxx, okuyama@xxxxxxxxxxxxxxxxx, matsui_v@xxxxxxxxxxxxx, kikuchi_v@xxxxxxxxxxxxx, fernando@xxxxxxxxxxxxxxxxx, kskmori@xxxxxxxxxxxxxxxxx, takenakak@xxxxxxxxxxxxxxxxx, yamaguchi@xxxxxxxxxxxxxxxxx, ext2-devel@xxxxxxxxxxxxxxxxxxxxx, sct@xxxxxxxxxx, shaggy@xxxxxxxxxxxxxx, linux-xfs@xxxxxxxxxxx, Reiserfs developers mail-list <Reiserfs-Dev@xxxxxxxxxxx>
In-reply-to: <42B067B6.9030009@xxxxxxxx>; from jeffm@xxxxxxxx on Wed, Jun 15, 2005 at 01:39:02PM -0400
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On Wed, Jun 15, 2005 at 01:39:02PM -0400, Jeff Mahoney wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hans Reiser wrote:
> > Jeff, would you be willing to make a proposal for what should be done? 
> > I would be interested in your suggestions.
> > 
> > Jeff Mahoney wrote:
> > 
> >>Hans -
> >>
> >>These tests must have been run on a kernel prior to 2.6.10-rc1. The I/O
> >>error code exhibits behavior similar to ext3, so (1b). There are still
> >>kinks to be worked out, but it's definitely not the "throw up our arms
> >>and give up" that it used to be.
> >>
> >>Implementing behavior 1a for ext3 and reiserfs should be fairly trivial
> >>- it just means that tests to check if the filesystem is in an aborted
> >>state ("shutdown" in xfs terms) need to added to the call path in some
> >>places, and be moved earlier in others.
> 
> Well it seems to me that all the XFS code does is check to see if the FS
> is in a shutdown state really early in the call path.

FYI, the up front checks in XFS are simply to stop new I/O from starting
if we're already in the shutdown state.

However, there's more than that in XFS - there's checks all through
it's I/O paths so that I/Os and transactions in flight at (or
started after) the time of the shutdown can be aborted before doing
further damage to a potentially corrupted filesystem. This part
cannot be done generically as it is intimately tied to the
filesystem.

It is also worth noting that XFS won't shutdown a filesystem on just
any I/O error. Shutdowns due to I/O errors only occur when the
failure has the potential to leave the filesystem in an inconsistent
state.  Hence any given operation can return different errors
depending on where the I/O error occurred in XFS and what effect
that I/O error has on the consistency of the filesystem.....

BTW, the correct list to use to get the attention of the XFS folk
is linux-xfs@xxxxxxxxxxxx

Cheers,

Dave.
-- 
Dave Chinner
R&D Software Engineer
SGI Australian Software Group


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