1 /* 2 * Functions related to generic timeout handling of requests. 3 */ 4 #include <linux/kernel.h> 5 #include <linux/module.h> 6 #include <linux/blkdev.h> 7 #include <linux/fault-inject.h> 8 9 #include "blk.h" 10 #include "blk-mq.h" 11 12 #ifdef CONFIG_FAIL_IO_TIMEOUT 13 14 static DECLARE_FAULT_ATTR(fail_io_timeout); 15 16 static int __init setup_fail_io_timeout(char *str) 17 { 18 return setup_fault_attr(&fail_io_timeout, str); 19 } 20 __setup("fail_io_timeout=", setup_fail_io_timeout); 21 22 int blk_should_fake_timeout(struct request_queue *q) 23 { 24 if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags)) 25 return 0; 26 27 return should_fail(&fail_io_timeout, 1); 28 } 29 30 static int __init fail_io_timeout_debugfs(void) 31 { 32 struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout", 33 NULL, &fail_io_timeout); 34 35 return PTR_ERR_OR_ZERO(dir); 36 } 37 38 late_initcall(fail_io_timeout_debugfs); 39 40 ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr, 41 char *buf) 42 { 43 struct gendisk *disk = dev_to_disk(dev); 44 int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags); 45 46 return sprintf(buf, "%d\n", set != 0); 47 } 48 49 ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr, 50 const char *buf, size_t count) 51 { 52 struct gendisk *disk = dev_to_disk(dev); 53 int val; 54 55 if (count) { 56 struct request_queue *q = disk->queue; 57 char *p = (char *) buf; 58 59 val = simple_strtoul(p, &p, 10); 60 if (val) 61 blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q); 62 else 63 blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q); 64 } 65 66 return count; 67 } 68 69 #endif /* CONFIG_FAIL_IO_TIMEOUT */ 70 71 /* 72 * blk_delete_timer - Delete/cancel timer for a given function. 73 * @req: request that we are canceling timer for 74 * 75 */ 76 void blk_delete_timer(struct request *req) 77 { 78 list_del_init(&req->timeout_list); 79 } 80 81 static void blk_rq_timed_out(struct request *req) 82 { 83 struct request_queue *q = req->q; 84 enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER; 85 86 if (q->rq_timed_out_fn) 87 ret = q->rq_timed_out_fn(req); 88 switch (ret) { 89 case BLK_EH_RESET_TIMER: 90 blk_add_timer(req); 91 blk_clear_rq_complete(req); 92 break; 93 case BLK_EH_DONE: 94 /* 95 * LLD handles this for now but in the future 96 * we can send a request msg to abort the command 97 * and we can move more of the generic scsi eh code to 98 * the blk layer. 99 */ 100 break; 101 default: 102 printk(KERN_ERR "block: bad eh return: %d\n", ret); 103 break; 104 } 105 } 106 107 static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout, 108 unsigned int *next_set) 109 { 110 const unsigned long deadline = blk_rq_deadline(rq); 111 112 if (time_after_eq(jiffies, deadline)) { 113 list_del_init(&rq->timeout_list); 114 115 /* 116 * Check if we raced with end io completion 117 */ 118 if (!blk_mark_rq_complete(rq)) 119 blk_rq_timed_out(rq); 120 } else if (!*next_set || time_after(*next_timeout, deadline)) { 121 *next_timeout = deadline; 122 *next_set = 1; 123 } 124 } 125 126 void blk_timeout_work(struct work_struct *work) 127 { 128 struct request_queue *q = 129 container_of(work, struct request_queue, timeout_work); 130 unsigned long flags, next = 0; 131 struct request *rq, *tmp; 132 int next_set = 0; 133 134 spin_lock_irqsave(q->queue_lock, flags); 135 136 list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) 137 blk_rq_check_expired(rq, &next, &next_set); 138 139 if (next_set) 140 mod_timer(&q->timeout, round_jiffies_up(next)); 141 142 spin_unlock_irqrestore(q->queue_lock, flags); 143 } 144 145 /** 146 * blk_abort_request -- Request request recovery for the specified command 147 * @req: pointer to the request of interest 148 * 149 * This function requests that the block layer start recovery for the 150 * request by deleting the timer and calling the q's timeout function. 151 * LLDDs who implement their own error recovery MAY ignore the timeout 152 * event if they generated blk_abort_req. Must hold queue lock. 153 */ 154 void blk_abort_request(struct request *req) 155 { 156 if (req->q->mq_ops) { 157 /* 158 * All we need to ensure is that timeout scan takes place 159 * immediately and that scan sees the new timeout value. 160 * No need for fancy synchronizations. 161 */ 162 blk_rq_set_deadline(req, jiffies); 163 kblockd_schedule_work(&req->q->timeout_work); 164 } else { 165 if (blk_mark_rq_complete(req)) 166 return; 167 blk_delete_timer(req); 168 blk_rq_timed_out(req); 169 } 170 } 171 EXPORT_SYMBOL_GPL(blk_abort_request); 172 173 unsigned long blk_rq_timeout(unsigned long timeout) 174 { 175 unsigned long maxt; 176 177 maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT); 178 if (time_after(timeout, maxt)) 179 timeout = maxt; 180 181 return timeout; 182 } 183 184 /** 185 * blk_add_timer - Start timeout timer for a single request 186 * @req: request that is about to start running. 187 * 188 * Notes: 189 * Each request has its own timer, and as it is added to the queue, we 190 * set up the timer. When the request completes, we cancel the timer. 191 */ 192 void blk_add_timer(struct request *req) 193 { 194 struct request_queue *q = req->q; 195 unsigned long expiry; 196 197 if (!q->mq_ops) 198 lockdep_assert_held(q->queue_lock); 199 200 /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */ 201 if (!q->mq_ops && !q->rq_timed_out_fn) 202 return; 203 204 BUG_ON(!list_empty(&req->timeout_list)); 205 206 /* 207 * Some LLDs, like scsi, peek at the timeout to prevent a 208 * command from being retried forever. 209 */ 210 if (!req->timeout) 211 req->timeout = q->rq_timeout; 212 213 req->rq_flags &= ~RQF_TIMED_OUT; 214 blk_rq_set_deadline(req, jiffies + req->timeout); 215 216 /* 217 * Only the non-mq case needs to add the request to a protected list. 218 * For the mq case we simply scan the tag map. 219 */ 220 if (!q->mq_ops) 221 list_add_tail(&req->timeout_list, &req->q->timeout_list); 222 223 /* 224 * If the timer isn't already pending or this timeout is earlier 225 * than an existing one, modify the timer. Round up to next nearest 226 * second. 227 */ 228 expiry = blk_rq_timeout(round_jiffies_up(blk_rq_deadline(req))); 229 230 if (!timer_pending(&q->timeout) || 231 time_before(expiry, q->timeout.expires)) { 232 unsigned long diff = q->timeout.expires - expiry; 233 234 /* 235 * Due to added timer slack to group timers, the timer 236 * will often be a little in front of what we asked for. 237 * So apply some tolerance here too, otherwise we keep 238 * modifying the timer because expires for value X 239 * will be X + something. 240 */ 241 if (!timer_pending(&q->timeout) || (diff >= HZ / 2)) 242 mod_timer(&q->timeout, expiry); 243 } 244 245 } 246