struct request documentation Jens Axboe 27/05/02 1.0 Index 2.0 Struct request members classification 2.1 struct request members explanation 3.0 2.0 Short explanation of request members Classification flags: D driver member B block layer member I I/O scheduler member Unless an entry contains a D classification, a device driver must not access this member. Some members may contain D classifications, but should only be access through certain macros or functions (eg ->flags). 2.1 Member Flag Comment ------ ---- ------- struct list_head queuelist BI Organization on various internal queues void *elevator_private I I/O scheduler private data unsigned char cmd[16] D Driver can use this for setting up a cdb before execution, see blk_queue_prep_rq unsigned long flags DBI Contains info about data direction, request type, etc. int rq_status D Request status bits kdev_t rq_dev DBI Target device int errors DB Error counts sector_t sector DBI Target location unsigned long hard_nr_sectors B Used to keep sector sane unsigned long nr_sectors DBI Total number of sectors in request unsigned long hard_nr_sectors B Used to keep nr_sectors sane unsigned short nr_phys_segments DB Number of physical scatter gather segments in a request unsigned short nr_hw_segments DB Number of hardware scatter gather segments in a request unsigned int current_nr_sectors DB Number of sectors in first segment of request unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane int tag DB TCQ tag, if assigned void *special D Free to be used by driver char *buffer D Map of first segment, also see section on bouncing SECTION struct completion *waiting D Can be used by driver to get signalled on request completion struct bio *bio DBI First bio in request struct bio *biotail DBI Last bio in request request_queue_t *q DB Request queue this request belongs to struct request_list *rl B Request list this request came from
