On Thu, Jan 14, 2010 at 12:33:54PM +1100, Dave Chinner wrote:
> When swapping extents, we can corrupt inodes by swapping data forks
> that are in incompatible formats. This is caused by the two indoes
> having different fork offsets due to the presence of an attribute
> fork on an attr2 filesystem. xfs_fsr tries to be smart about
> setting the fork offset, but the trick it plays only works on attr1
> (old fixed format attribute fork) filesystems.
> Changing the way xfs_fsr sets up the attribute fork will prevent
> this situation from ever occurring, so in the kernel code we can get
> by with a preventative fix - check that the data fork in the
> defragmented inode is in a format valid for the inode it is being
> swapped into. This will lead to files that will silently and
> potentially repeatedly fail defragmentation, so issue a warning to
> the log when this particular failure occurs to let us know that
> xfs_fsr needs updating/fixing.
> To help identify how to improve xfs_fsr to avoid this issue, add
> trace points for the inodes being swapped so that we can determine
> why the swap was rejected and to confirm that the code is making the
> right decisions and modifications when swapping forks.
> A further complication is even when the swap is allowed to proceed
> when the fork offset is different between the two inodes then value
> for the maximum number of extents the data fork can hold can be
> wrong. Make sure these are also set correctly after the swap occurs.
> Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
> fs/xfs/xfs_dfrag.c | 106
Reviewed-by: Christoph Hellwig <hch@xxxxxx>