xfs_repair Input/output error

[Cory Coager <ccoager@xxxxxxxxx>]

I had a power failure while I was running a
defrag on an xfs partition. Now I am unable to mount, xfs_check or
xfs_repair the partition. The partition is lvm and all other partitions
seem to be fine except this one. When attempting to mount the partition
the drive makes some funny noises and these messages spit out on the
console:

hda: dma_intr: status=0x51 { DriveReady SeekComplete Error }
hda: dma_intr: error=0x40 { UncorrectableError }, LBAsect=268552872, high=16, low=117416, sector=268552868
ide: failed opcode was: unknown
end_request: I/O error, dev hda, sector 268552868

I believe the drive is fine because check_ide_smart reports:

Id=  1, Status=11 {PreFailure , OnLine }, Value=100, Threshold= 60, Passed
Id=  2, Status= 5 {PreFailure , OffLine}, Value=100, Threshold= 50, Passed
Id=  3, Status= 7 {PreFailure , OnLine }, Value=151, Threshold= 24, Passed
Id=  4, Status=18 {Advisory    , OnLine }, Value=100, Threshold=  0, Passed
Id=  5, Status=51 {PreFailure , OnLine }, Value=100, Threshold=  5, Passed
Id=  7, Status=11 {PreFailure , OnLine }, Value=100, Threshold= 67, Passed
Id=  8, Status= 5 {PreFailure , OffLine}, Value=100, Threshold= 20, Passed
Id=  9, Status=18 {Advisory    , OnLine }, Value= 96, Threshold=  0, Passed
Id= 10, Status=19 {PreFailure , OnLine }, Value=100, Threshold= 60, Passed
Id= 12, Status=50 {Advisory    , OnLine }, Value=100, Threshold=  0, Passed
Id=192, Status=50 {Advisory    , OnLine }, Value= 99, Threshold= 50, Passed
Id=193, Status=18 {Advisory    , OnLine }, Value= 99, Threshold= 50, Passed
Id=194, Status= 2 {Advisory    , OnLine }, Value=137, Threshold=  0, Passed
Id=196, Status=50 {Advisory    , OnLine }, Value=100, Threshold=  0, Passed
Id=197, Status=34 {Advisory    , OnLine }, Value=100, Threshold=  0, Passed
Id=198, Status= 8 {Advisory    , OffLine}, Value=100, Threshold=  0, Passed
Id=199, Status=10 {Advisory    , OnLine }, Value=200, Threshold=  0, Passed
OffLineStatus=0 {NeverStarted}, AutoOffLine=No, OffLineTimeout=92 minutes
OffLineCapability=27 {Immediate Auto SuspendOnCmd}
SmartRevision=16, CheckSum=151, SmartCapability=3 {SaveOnStandBy AutoSave}

I can xxd and dd this partition without getting any console errors.
I can also mount the partition with -o ro,norecovery.  
How do I repair this and recover my data?