* Doing kmalloc() in the middle of command execution is not only ugly
  but leaves drive waiting to send data on kmalloc() failure.  Fix it.

While at it:

* Unify error code paths.

* Fixup error message to be more useful and add missing KERN_ERR level.

* Rename 'stat' variable to 's'.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>