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
