Port the fix of bug 18801 to 2.1
LU-3192 LBUG:(osc_request.c:1308:osc_brw_prep_request()) ASSERTION( i == 0 || pg->off > pg_prev->off )
LU-13805 i/o path: Unaligned direct i/o
LU-12429 Single client buffered SSF write is slower than O_DIRECT
LU-4664 sync write should consume grant on client
LU-4198 Improve IO performance when using DIRECT IO using libaio