On 09/04/2018 12:19 PM, Greg Edwards wrote: > When T10 PI is enabled on a backing device for the iblock backstore, the > PI SGL for the entire command is attached to the first bio only. This > works fine if the command is covered by a single bio, but can result in > ref tag errors in the client for the other bios in a multi-bio command, > e.g. > > [ 47.631236] sda: ref tag error at location 2048 (rcvd 0) > [ 47.637658] sda: ref tag error at location 4096 (rcvd 0) > [ 47.644228] sda: ref tag error at location 6144 (rcvd 0) > > The command will be split into multiple bios if the number of data SG > elements exceeds BIO_MAX_PAGES (see iblock_get_bio()). > > The bios may later be split again in the block layer on the host after > iblock_submit_bios(), depending on the queue limits of the backing > device. The block and SCSI layers will pass through the whole PI SGL > down to the LLDD however that first bio is split up, but the LLDD may > only use the portion that corresponds to the data length (depends on the > LLDD, tested with scsi_debug). > > Split the PI SGL across the bios in the command, so each bio's > bio_integrity_payload contains the protection information for the data > in the bio. Use an sg_mapping_iter to keep track of where we are in PI > SGL, so we know where to start with the next bio. > > Signed-off-by: Greg Edwards <gedwards@xxxxxxx> > --- > Changes from v4: > * use %zu for size_t in pr_debug() > > Changes from v3: > * cast a size_t as unsigned long in a pr_debug() for 32-bit arches, > turned up by the kbuild test robot > > Changes from v2: > * add back min(cmd->t_prot_nents, BIO_MAX_PAGES) for bio_integrity_alloc() > from v1 > > Changes from v1: > * expand commit message > * use an sg_mapping_iter to track where we are in the PI SGL > Looks ok to me. Reviewed-by: Mike Christie <mchristi@xxxxxxxxxx>
