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Re: Failure growing xfs with linux 3.10.5

To: Michael Maier <m1278468@xxxxxxxxxxx>
Subject: Re: Failure growing xfs with linux 3.10.5
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 15 Aug 2013 10:58:09 +1000
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <520B9F3E.6030805@xxxxxxxxxxx>
References: <52073905.8010608@xxxxxxxxxxx> <5207D9C4.7020102@xxxxxxxxxxx> <5209126F.5020204@xxxxxxxxxxx> <20130813005414.GT12779@dastard> <520A48C4.6060801@xxxxxxxxxxx> <20130814054332.GA12779@dastard> <520B9F3E.6030805@xxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Aug 14, 2013 at 05:16:14PM +0200, Michael Maier wrote:
> Dave Chinner wrote:
> > On Tue, Aug 13, 2013 at 04:55:00PM +0200, Michael Maier wrote:
> >> Dave Chinner wrote:
> >>> On Mon, Aug 12, 2013 at 06:50:55PM +0200, Michael Maier wrote:
> >>>> Meanwhile, I faced another problem on another xfs-file system with linux
> >>>> 3.10.5 which I never saw before. During writing a few bytes to disc, I
> >>>> got "disc full" and the writing failed.
> >>>>
> >>>> At the same time, df reported 69G of free space! I ran xfs_repair -n and
> >>>> got:
> >>>>
> >>>>
> >>>> xfs_repair -n /dev/mapper/raid0-daten2
> >>>> Phase 1 - find and verify superblock...
> >>>> Phase 2 - using internal log
> >>>>         - scan filesystem freespace and inode maps...
> >>>> sb_ifree 591, counted 492
> >>>> ^^^^^^^^^^^^^^^^^^^^^^^^^
> >>>> What does this mean? How can I get rid of it w/o loosing data? This file
> >>>> system was created a few days ago and never resized.
> >>>
> >>> Superblock inode counting is lazy - it can get out of sync in after
> >>> an unclean shutdown, but generally mounting a dirty filesystem will
> >>> result in it being recalculated rather than trusted to be correct.
> >>> So there's nothing to worry about here.
> >>
> >> When will it be self healed?
> > 
> > that depends on whether there's actually a problem. Like I said in
> > the part you snipped off - if you ran xfs_repair -n on filesystem
> > that needs log recovery that accounting difference is expected.
> I know, that option -n doesn't do anything. It was intended, because
> xfs_repair destroyed a lot of data when applied at the other problem I
> have _and_ it repaired nothing at the same time!

xfs_repair will remove files it cannot repair because their metadata
is are too corrupted to repair or cannot be repaired safely. That's
always been the case for any filesystem repair tool - all they
guarantee is that the filesystem will be consistent after they are
run. Repairing a corrupted filesystem almost always results in some
form of data loss occurring....

If there is nothing wrong with the filesystem except the accouting
is wrong, then it will fix the accounting problem in phase 5 when
run without the -n parameter.

> >> This is strange and I can't use the free space, which I need! How can it
> >> be forced to be repaired w/o data loss?
> > 
> > The above is complaining about a free inode count mismatch, not a
> > problem about free space being wrong. What problem are you actually
> > having?
> The application, which wanted to write a few bytes gets a "disk full"
> error although df -h reports 69GB of free space.

That's not necessarily a corruption, though, and most likely isn't
related to the accounting issue xfs_repair is reporting. Indeed,
this is typically a sign of being unable to allocate an inode
because there is insufficient contiguous free space in the
filesystem to allocate a new inode chunk. What does your free space
histogram look like?

# xfs_db -r -c "freesp -s" <dev>


Dave Chinner

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