1/* 2 * Functions related to barrier IO handling 3 */ 4#include <linux/kernel.h> 5#include <linux/module.h> 6#include <linux/bio.h> 7#include <linux/blkdev.h> 8#include <linux/gfp.h> 9 10#include "blk.h" 11 12/** 13 * blk_queue_ordered - does this queue support ordered writes 14 * @q: the request queue 15 * @ordered: one of QUEUE_ORDERED_* 16 * 17 * Description: 18 * For journalled file systems, doing ordered writes on a commit 19 * block instead of explicitly doing wait_on_buffer (which is bad 20 * for performance) can be a big win. Block drivers supporting this 21 * feature should call this function and indicate so. 22 * 23 **/ 24int blk_queue_ordered(struct request_queue *q, unsigned ordered) 25{ 26 if (ordered != QUEUE_ORDERED_NONE && 27 ordered != QUEUE_ORDERED_DRAIN && 28 ordered != QUEUE_ORDERED_DRAIN_FLUSH && 29 ordered != QUEUE_ORDERED_DRAIN_FUA && 30 ordered != QUEUE_ORDERED_TAG && 31 ordered != QUEUE_ORDERED_TAG_FLUSH && 32 ordered != QUEUE_ORDERED_TAG_FUA) { 33 printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered); 34 return -EINVAL; 35 } 36 37 q->ordered = ordered; 38 q->next_ordered = ordered; 39 40 return 0; 41} 42EXPORT_SYMBOL(blk_queue_ordered); 43 44/* 45 * Cache flushing for ordered writes handling 46 */ 47unsigned blk_ordered_cur_seq(struct request_queue *q) 48{ 49 if (!q->ordseq) 50 return 0; 51 return 1 << ffz(q->ordseq); 52} 53 54unsigned blk_ordered_req_seq(struct request *rq) 55{ 56 struct request_queue *q = rq->q; 57 58 BUG_ON(q->ordseq == 0); 59 60 if (rq == &q->pre_flush_rq) 61 return QUEUE_ORDSEQ_PREFLUSH; 62 if (rq == &q->bar_rq) 63 return QUEUE_ORDSEQ_BAR; 64 if (rq == &q->post_flush_rq) 65 return QUEUE_ORDSEQ_POSTFLUSH; 66 67 /* 68 * !fs requests don't need to follow barrier ordering. Always 69 * put them at the front. This fixes the following deadlock. 70 * 71 * http://thread.gmane.org/gmane.linux.kernel/537473 72 */ 73 if (rq->cmd_type != REQ_TYPE_FS) 74 return QUEUE_ORDSEQ_DRAIN; 75 76 if ((rq->cmd_flags & REQ_ORDERED_COLOR) == 77 (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR)) 78 return QUEUE_ORDSEQ_DRAIN; 79 else 80 return QUEUE_ORDSEQ_DONE; 81} 82 83bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error) 84{ 85 struct request *rq; 86 87 if (error && !q->orderr) 88 q->orderr = error; 89 90 BUG_ON(q->ordseq & seq); 91 q->ordseq |= seq; 92 93 if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE) 94 return false; 95 96 /* 97 * Okay, sequence complete. 98 */ 99 q->ordseq = 0; 100 rq = q->orig_bar_rq; 101 __blk_end_request_all(rq, q->orderr); 102 return true; 103} 104 105static void pre_flush_end_io(struct request *rq, int error) 106{ 107 elv_completed_request(rq->q, rq); 108 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error); 109} 110 111static void bar_end_io(struct request *rq, int error) 112{ 113 elv_completed_request(rq->q, rq); 114 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error); 115} 116 117static void post_flush_end_io(struct request *rq, int error) 118{ 119 elv_completed_request(rq->q, rq); 120 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error); 121} 122 123static void queue_flush(struct request_queue *q, unsigned which) 124{ 125 struct request *rq; 126 rq_end_io_fn *end_io; 127 128 if (which == QUEUE_ORDERED_DO_PREFLUSH) { 129 rq = &q->pre_flush_rq; 130 end_io = pre_flush_end_io; 131 } else { 132 rq = &q->post_flush_rq; 133 end_io = post_flush_end_io; 134 } 135 136 blk_rq_init(q, rq); 137 rq->cmd_type = REQ_TYPE_FS; 138 rq->cmd_flags = REQ_HARDBARRIER | REQ_FLUSH; 139 rq->rq_disk = q->orig_bar_rq->rq_disk; 140 rq->end_io = end_io; 141 142 elv_insert(q, rq, ELEVATOR_INSERT_FRONT); 143} 144 145static inline bool start_ordered(struct request_queue *q, struct request **rqp) 146{ 147 struct request *rq = *rqp; 148 unsigned skip = 0; 149 150 q->orderr = 0; 151 q->ordered = q->next_ordered; 152 q->ordseq |= QUEUE_ORDSEQ_STARTED; 153 154 /* 155 * For an empty barrier, there's no actual BAR request, which 156 * in turn makes POSTFLUSH unnecessary. Mask them off. 157 */ 158 if (!blk_rq_sectors(rq)) { 159 q->ordered &= ~(QUEUE_ORDERED_DO_BAR | 160 QUEUE_ORDERED_DO_POSTFLUSH); 161 /* 162 * Empty barrier on a write-through device w/ ordered 163 * tag has no command to issue and without any command 164 * to issue, ordering by tag can't be used. Drain 165 * instead. 166 */ 167 if ((q->ordered & QUEUE_ORDERED_BY_TAG) && 168 !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) { 169 q->ordered &= ~QUEUE_ORDERED_BY_TAG; 170 q->ordered |= QUEUE_ORDERED_BY_DRAIN; 171 } 172 } 173 174 /* stash away the original request */ 175 blk_dequeue_request(rq); 176 q->orig_bar_rq = rq; 177 rq = NULL; 178 179 /* 180 * Queue ordered sequence. As we stack them at the head, we 181 * need to queue in reverse order. Note that we rely on that 182 * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs 183 * request gets inbetween ordered sequence. 184 */ 185 if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) { 186 queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH); 187 rq = &q->post_flush_rq; 188 } else 189 skip |= QUEUE_ORDSEQ_POSTFLUSH; 190 191 if (q->ordered & QUEUE_ORDERED_DO_BAR) { 192 rq = &q->bar_rq; 193 194 /* initialize proxy request and queue it */ 195 blk_rq_init(q, rq); 196 if (bio_data_dir(q->orig_bar_rq->bio) == WRITE) 197 rq->cmd_flags |= REQ_WRITE; 198 if (q->ordered & QUEUE_ORDERED_DO_FUA) 199 rq->cmd_flags |= REQ_FUA; 200 init_request_from_bio(rq, q->orig_bar_rq->bio); 201 rq->end_io = bar_end_io; 202 203 elv_insert(q, rq, ELEVATOR_INSERT_FRONT); 204 } else 205 skip |= QUEUE_ORDSEQ_BAR; 206 207 if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) { 208 queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH); 209 rq = &q->pre_flush_rq; 210 } else 211 skip |= QUEUE_ORDSEQ_PREFLUSH; 212 213 if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q)) 214 rq = NULL; 215 else 216 skip |= QUEUE_ORDSEQ_DRAIN; 217 218 *rqp = rq; 219 220 /* 221 * Complete skipped sequences. If whole sequence is complete, 222 * return false to tell elevator that this request is gone. 223 */ 224 return !blk_ordered_complete_seq(q, skip, 0); 225} 226 227bool blk_do_ordered(struct request_queue *q, struct request **rqp) 228{ 229 struct request *rq = *rqp; 230 const int is_barrier = rq->cmd_type == REQ_TYPE_FS && 231 (rq->cmd_flags & REQ_HARDBARRIER); 232 233 if (!q->ordseq) { 234 if (!is_barrier) 235 return true; 236 237 if (q->next_ordered != QUEUE_ORDERED_NONE) 238 return start_ordered(q, rqp); 239 else { 240 /* 241 * Queue ordering not supported. Terminate 242 * with prejudice. 243 */ 244 blk_dequeue_request(rq); 245 __blk_end_request_all(rq, -EOPNOTSUPP); 246 *rqp = NULL; 247 return false; 248 } 249 } 250 251 /* 252 * Ordered sequence in progress 253 */ 254 255 /* Special requests are not subject to ordering rules. */ 256 if (rq->cmd_type != REQ_TYPE_FS && 257 rq != &q->pre_flush_rq && rq != &q->post_flush_rq) 258 return true; 259 260 if (q->ordered & QUEUE_ORDERED_BY_TAG) { 261 /* Ordered by tag. Blocking the next barrier is enough. */ 262 if (is_barrier && rq != &q->bar_rq) 263 *rqp = NULL; 264 } else { 265 /* Ordered by draining. Wait for turn. */ 266 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q)); 267 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q)) 268 *rqp = NULL; 269 } 270 271 return true; 272} 273 274static void bio_end_empty_barrier(struct bio *bio, int err) 275{ 276 if (err) { 277 if (err == -EOPNOTSUPP) 278 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); 279 clear_bit(BIO_UPTODATE, &bio->bi_flags); 280 } 281 if (bio->bi_private) 282 complete(bio->bi_private); 283 bio_put(bio); 284} 285 286/** 287 * blkdev_issue_flush - queue a flush 288 * @bdev: blockdev to issue flush for 289 * @gfp_mask: memory allocation flags (for bio_alloc) 290 * @error_sector: error sector 291 * @flags: BLKDEV_IFL_* flags to control behaviour 292 * 293 * Description: 294 * Issue a flush for the block device in question. Caller can supply 295 * room for storing the error offset in case of a flush error, if they 296 * wish to. If WAIT flag is not passed then caller may check only what 297 * request was pushed in some internal queue for later handling. 298 */ 299int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask, 300 sector_t *error_sector, unsigned long flags) 301{ 302 DECLARE_COMPLETION_ONSTACK(wait); 303 struct request_queue *q; 304 struct bio *bio; 305 int ret = 0; 306 307 if (bdev->bd_disk == NULL) 308 return -ENXIO; 309 310 q = bdev_get_queue(bdev); 311 if (!q) 312 return -ENXIO; 313 314 /* 315 * some block devices may not have their queue correctly set up here 316 * (e.g. loop device without a backing file) and so issuing a flush 317 * here will panic. Ensure there is a request function before issuing 318 * the barrier. 319 */ 320 if (!q->make_request_fn) 321 return -ENXIO; 322 323 bio = bio_alloc(gfp_mask, 0); 324 bio->bi_end_io = bio_end_empty_barrier; 325 bio->bi_bdev = bdev; 326 if (test_bit(BLKDEV_WAIT, &flags)) 327 bio->bi_private = &wait; 328 329 bio_get(bio); 330 submit_bio(WRITE_BARRIER, bio); 331 if (test_bit(BLKDEV_WAIT, &flags)) { 332 wait_for_completion(&wait); 333 /* 334 * The driver must store the error location in ->bi_sector, if 335 * it supports it. For non-stacked drivers, this should be 336 * copied from blk_rq_pos(rq). 337 */ 338 if (error_sector) 339 *error_sector = bio->bi_sector; 340 } 341 342 if (bio_flagged(bio, BIO_EOPNOTSUPP)) 343 ret = -EOPNOTSUPP; 344 else if (!bio_flagged(bio, BIO_UPTODATE)) 345 ret = -EIO; 346 347 bio_put(bio); 348 return ret; 349} 350EXPORT_SYMBOL(blkdev_issue_flush); 351