On 06/05/2014 09:02 AM, Douglas Gilbert wrote: > After the SG_IO ioctl was copied into the block layer and > later into the bsg driver, subtle differences emerged. > > One difference is the way injected commands are queued through > the block layer (i.e. this is not SCSI device queueing nor SATA > NCQ). Summarizing: > - SG_IO on block layer device: blk_exec*(at_head=false) > - sg device SG_IO: at_head=true > - bsg device SG_IO: at_head=true > > Some time ago Boaz Harrosh introduced a sg v4 flag called > BSG_FLAG_Q_AT_TAIL to override the bsg driver default. A > recent patch titled: "sg: add SG_FLAG_Q_AT_TAIL flag" > allowed the sg driver default to be overridden. This patch > allows a SG_IO ioctl sent to a block layer device to have > its default overridden. > > ChangeLog: > - introduce SG_FLAG_Q_AT_HEAD flag in sg.h to cause > commands that are injected via a block layer > device SG_IO ioctl to set at_head=true > - make comments clearer about queueing in sg.h since the > header is used both by the sg device and block layer > device implementations of the SG_IO ioctl. > - introduce BSG_FLAG_Q_AT_HEAD in bsg.h for compatibility > (it does nothing) and update comments. > > > Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx> Looks ok to me. Reviewed-by: Mike Christie <michaelc@xxxxxxxxxxx> -- 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
