b=21137 sles11 with 1.8 is slower than 1.6 sles10 for O_DIRECT single file IOR writes

 Fix __bio_add_page() in order to prevent IO split on some drivers.

 i=andreas.dilger
 i=sheng.yang

 This patch comes from the kernel commit

Gitweb:     http://git.kernel.org/linus/8a78362c4eefc1deddbefe2c7f38aabbc2429d6b
Commit:     8a78362c4eefc1deddbefe2c7f38aabbc2429d6b
Parent:     086fa5ff0854c676ec333760f4c0154b3b242616
Author:     Martin K. Petersen <martin.petersen@oracle.com>
AuthorDate: Fri Feb 26 00:20:39 2010 -0500
Committer:  Jens Axboe <jens.axboe@oracle.com>
CommitDate: Fri Feb 26 13:58:08 2010 +0100

    block: Consolidate phys_segment and hw_segment limits

    Except for SCSI no device drivers distinguish between physical and
    hardware segment limits.  Consolidate the two into a single segment
    limit.