----- Original Message ----- > From: "Eyal Ben David" <bdeyal@xxxxxxxxx> > To: linux-scsi@xxxxxxxxxxxxxxx > Sent: Sunday, November 20, 2016 11:02:49 AM > Subject: SG does not ignore dxferp (direct io + mmap) > > Hi all, > > We have some IO utility that perform the IOs using sg and direct io with > mmap. > Our current systems are Ubuntu 14.04, RHEL 6,7 > The IO utility always set dxferp to either the address or mmap of > other allocation (valloc) > Setting dxferp was harmless since SG is supposed to ignore the address > if mmap IO is selected. > When porting to Ubuntu 16.04, we had a corruption problem - first byte > of a read task is always 0. > When setting dxferp as NULL the corruption does not occur any more. > This is a regression and not according to SCSI generic documentation. > > I wrote a small program that shows the change: > > Read indirect (no mmap), lba=0: > ======================= > $ ./sg_mmap_read -d /dev/sg0 -l 0 > 0000000 eb 63 90 10 8e d0 bc 00 b0 b8 00 00 8e d8 8e c0 > > Read with mmap, lba=0, dxferp=NULL: > ============================ > $ ./sg_mmap_read -d /dev/sg0 -l 0 -m > 0000000 eb 63 90 10 8e d0 bc 00 b0 b8 00 00 8e d8 8e c0 > > Read with mmap, lba=0, dxferp=address from mmap > ====================================== > $ ./sg_mmap_read -d /dev/sg0 -l 0 -m -b > 0000000 00 63 90 10 8e d0 bc 00 b0 b8 00 00 8e d8 8e c0 > > On the older systems all results are the same. > > Thanks for any answer! > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Hello Given that we cannot see what your utility (sg_mmap_read) is doing, can we get the source for that or an strace of your test here. I am sure Doug will then be able to help you. Thanks Laurence -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
