[$] Ext4 data corruption hits the stable kernels

The kernel's stable-update process is intended to produce kernels that are,well, stable; when that promise is lived up to, users can update to newerstable updates without fear. By any account, a bug that corrupts data onext4 filesystems constitutes a failure to hold to that promise. As is sooften the case, this problem is the result of a chain of failures in asystem that works well most of the time.