commit e013e13bf605b9e6b702adffbe2853cfc60e7806
Author: Jens Axboe <jens.axboe@oracle.com>
Date:   Fri Oct 24 09:22:42 2008 +0200

    libata: fix bug with non-ncq devices
    
    The recent commit 2fca5ccf97d2c28bcfce44f5b07d85e74e3cd18e ("libata:
    switch to using block layer tagging support") to enable support for
    block layer tagging in libata was broken for non-NCQ devices
    
    The block layer initializes the tag field to -1 to detect invalid uses
    of a tag, and if the libata devices does NOT support NCQ, we just used
    that field to index the internal command list.  So we need to check for
    -1 first and only use the tag field if it's valid.
    
    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
    Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
    Tested-by: Paul Mundt <lethal@linux-sh.org>
    Tested-by: Dave Young <hidave.darkstar@gmail.com>
    Tested-by: Rafael J. Wysocki <rjw@sisk.pl>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>