| Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame^] | 1 | |
| 2 | struct request documentation |
| 3 | |
| 4 | Jens Axboe <jens.axboe@oracle.com> 27/05/02 |
| 5 | |
| 6 | 1.0 |
| 7 | Index |
| 8 | |
| 9 | 2.0 Struct request members classification |
| 10 | |
| 11 | 2.1 struct request members explanation |
| 12 | |
| 13 | 3.0 |
| 14 | |
| 15 | |
| 16 | 2.0 |
| 17 | Short explanation of request members |
| 18 | |
| 19 | Classification flags: |
| 20 | |
| 21 | D driver member |
| 22 | B block layer member |
| 23 | I I/O scheduler member |
| 24 | |
| 25 | Unless an entry contains a D classification, a device driver must not access |
| 26 | this member. Some members may contain D classifications, but should only be |
| 27 | access through certain macros or functions (eg ->flags). |
| 28 | |
| 29 | <linux/blkdev.h> |
| 30 | |
| 31 | 2.1 |
| 32 | Member Flag Comment |
| 33 | ------ ---- ------- |
| 34 | |
| 35 | struct list_head queuelist BI Organization on various internal |
| 36 | queues |
| 37 | |
| 38 | void *elevator_private I I/O scheduler private data |
| 39 | |
| 40 | unsigned char cmd[16] D Driver can use this for setting up |
| 41 | a cdb before execution, see |
| 42 | blk_queue_prep_rq |
| 43 | |
| 44 | unsigned long flags DBI Contains info about data direction, |
| 45 | request type, etc. |
| 46 | |
| 47 | int rq_status D Request status bits |
| 48 | |
| 49 | kdev_t rq_dev DBI Target device |
| 50 | |
| 51 | int errors DB Error counts |
| 52 | |
| 53 | sector_t sector DBI Target location |
| 54 | |
| 55 | unsigned long hard_nr_sectors B Used to keep sector sane |
| 56 | |
| 57 | unsigned long nr_sectors DBI Total number of sectors in request |
| 58 | |
| 59 | unsigned long hard_nr_sectors B Used to keep nr_sectors sane |
| 60 | |
| 61 | unsigned short nr_phys_segments DB Number of physical scatter gather |
| 62 | segments in a request |
| 63 | |
| 64 | unsigned short nr_hw_segments DB Number of hardware scatter gather |
| 65 | segments in a request |
| 66 | |
| 67 | unsigned int current_nr_sectors DB Number of sectors in first segment |
| 68 | of request |
| 69 | |
| 70 | unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane |
| 71 | |
| 72 | int tag DB TCQ tag, if assigned |
| 73 | |
| 74 | void *special D Free to be used by driver |
| 75 | |
| 76 | char *buffer D Map of first segment, also see |
| 77 | section on bouncing SECTION |
| 78 | |
| 79 | struct completion *waiting D Can be used by driver to get signalled |
| 80 | on request completion |
| 81 | |
| 82 | struct bio *bio DBI First bio in request |
| 83 | |
| 84 | struct bio *biotail DBI Last bio in request |
| 85 | |
| 86 | struct request_queue *q DB Request queue this request belongs to |
| 87 | |
| 88 | struct request_list *rl B Request list this request came from |