| 1 | /* |
| 2 | * Functions to sequence FLUSH and FUA writes. |
| 3 | * |
| 4 | * Copyright (C) 2011 Max Planck Institute for Gravitational Physics |
| 5 | * Copyright (C) 2011 Tejun Heo <tj@kernel.org> |
| 6 | * |
| 7 | * This file is released under the GPLv2. |
| 8 | * |
| 9 | * REQ_{FLUSH|FUA} requests are decomposed to sequences consisted of three |
| 10 | * optional steps - PREFLUSH, DATA and POSTFLUSH - according to the request |
| 11 | * properties and hardware capability. |
| 12 | * |
| 13 | * If a request doesn't have data, only REQ_PREFLUSH makes sense, which |
| 14 | * indicates a simple flush request. If there is data, REQ_PREFLUSH indicates |
| 15 | * that the device cache should be flushed before the data is executed, and |
| 16 | * REQ_FUA means that the data must be on non-volatile media on request |
| 17 | * completion. |
| 18 | * |
| 19 | * If the device doesn't have writeback cache, FLUSH and FUA don't make any |
| 20 | * difference. The requests are either completed immediately if there's no |
| 21 | * data or executed as normal requests otherwise. |
| 22 | * |
| 23 | * If the device has writeback cache and supports FUA, REQ_PREFLUSH is |
| 24 | * translated to PREFLUSH but REQ_FUA is passed down directly with DATA. |
| 25 | * |
| 26 | * If the device has writeback cache and doesn't support FUA, REQ_PREFLUSH |
| 27 | * is translated to PREFLUSH and REQ_FUA to POSTFLUSH. |
| 28 | * |
| 29 | * The actual execution of flush is double buffered. Whenever a request |
| 30 | * needs to execute PRE or POSTFLUSH, it queues at |
| 31 | * fq->flush_queue[fq->flush_pending_idx]. Once certain criteria are met, a |
| 32 | * REQ_OP_FLUSH is issued and the pending_idx is toggled. When the flush |
| 33 | * completes, all the requests which were pending are proceeded to the next |
| 34 | * step. This allows arbitrary merging of different types of FLUSH/FUA |
| 35 | * requests. |
| 36 | * |
| 37 | * Currently, the following conditions are used to determine when to issue |
| 38 | * flush. |
| 39 | * |
| 40 | * C1. At any given time, only one flush shall be in progress. This makes |
| 41 | * double buffering sufficient. |
| 42 | * |
| 43 | * C2. Flush is deferred if any request is executing DATA of its sequence. |
| 44 | * This avoids issuing separate POSTFLUSHes for requests which shared |
| 45 | * PREFLUSH. |
| 46 | * |
| 47 | * C3. The second condition is ignored if there is a request which has |
| 48 | * waited longer than FLUSH_PENDING_TIMEOUT. This is to avoid |
| 49 | * starvation in the unlikely case where there are continuous stream of |
| 50 | * FUA (without FLUSH) requests. |
| 51 | * |
| 52 | * For devices which support FUA, it isn't clear whether C2 (and thus C3) |
| 53 | * is beneficial. |
| 54 | * |
| 55 | * Note that a sequenced FLUSH/FUA request with DATA is completed twice. |
| 56 | * Once while executing DATA and again after the whole sequence is |
| 57 | * complete. The first completion updates the contained bio but doesn't |
| 58 | * finish it so that the bio submitter is notified only after the whole |
| 59 | * sequence is complete. This is implemented by testing RQF_FLUSH_SEQ in |
| 60 | * req_bio_endio(). |
| 61 | * |
| 62 | * The above peculiarity requires that each FLUSH/FUA request has only one |
| 63 | * bio attached to it, which is guaranteed as they aren't allowed to be |
| 64 | * merged in the usual way. |
| 65 | */ |
| 66 | |
| 67 | #include <linux/kernel.h> |
| 68 | #include <linux/module.h> |
| 69 | #include <linux/bio.h> |
| 70 | #include <linux/blkdev.h> |
| 71 | #include <linux/gfp.h> |
| 72 | #include <linux/blk-mq.h> |
| 73 | |
| 74 | #include "blk.h" |
| 75 | #include "blk-mq.h" |
| 76 | #include "blk-mq-tag.h" |
| 77 | #include "blk-mq-sched.h" |
| 78 | |
| 79 | /* FLUSH/FUA sequences */ |
| 80 | enum { |
| 81 | REQ_FSEQ_PREFLUSH = (1 << 0), /* pre-flushing in progress */ |
| 82 | REQ_FSEQ_DATA = (1 << 1), /* data write in progress */ |
| 83 | REQ_FSEQ_POSTFLUSH = (1 << 2), /* post-flushing in progress */ |
| 84 | REQ_FSEQ_DONE = (1 << 3), |
| 85 | |
| 86 | REQ_FSEQ_ACTIONS = REQ_FSEQ_PREFLUSH | REQ_FSEQ_DATA | |
| 87 | REQ_FSEQ_POSTFLUSH, |
| 88 | |
| 89 | /* |
| 90 | * If flush has been pending longer than the following timeout, |
| 91 | * it's issued even if flush_data requests are still in flight. |
| 92 | */ |
| 93 | FLUSH_PENDING_TIMEOUT = 5 * HZ, |
| 94 | }; |
| 95 | |
| 96 | static bool blk_kick_flush(struct request_queue *q, |
| 97 | struct blk_flush_queue *fq); |
| 98 | |
| 99 | static unsigned int blk_flush_policy(unsigned long fflags, struct request *rq) |
| 100 | { |
| 101 | unsigned int policy = 0; |
| 102 | |
| 103 | if (blk_rq_sectors(rq)) |
| 104 | policy |= REQ_FSEQ_DATA; |
| 105 | |
| 106 | if (fflags & (1UL << QUEUE_FLAG_WC)) { |
| 107 | if (rq->cmd_flags & REQ_PREFLUSH) |
| 108 | policy |= REQ_FSEQ_PREFLUSH; |
| 109 | if (!(fflags & (1UL << QUEUE_FLAG_FUA)) && |
| 110 | (rq->cmd_flags & REQ_FUA)) |
| 111 | policy |= REQ_FSEQ_POSTFLUSH; |
| 112 | } |
| 113 | return policy; |
| 114 | } |
| 115 | |
| 116 | static unsigned int blk_flush_cur_seq(struct request *rq) |
| 117 | { |
| 118 | return 1 << ffz(rq->flush.seq); |
| 119 | } |
| 120 | |
| 121 | static void blk_flush_restore_request(struct request *rq) |
| 122 | { |
| 123 | /* |
| 124 | * After flush data completion, @rq->bio is %NULL but we need to |
| 125 | * complete the bio again. @rq->biotail is guaranteed to equal the |
| 126 | * original @rq->bio. Restore it. |
| 127 | */ |
| 128 | rq->bio = rq->biotail; |
| 129 | |
| 130 | /* make @rq a normal request */ |
| 131 | rq->rq_flags &= ~RQF_FLUSH_SEQ; |
| 132 | rq->end_io = rq->flush.saved_end_io; |
| 133 | } |
| 134 | |
| 135 | static bool blk_flush_queue_rq(struct request *rq, bool add_front) |
| 136 | { |
| 137 | if (rq->q->mq_ops) { |
| 138 | blk_mq_add_to_requeue_list(rq, add_front, true); |
| 139 | return false; |
| 140 | } else { |
| 141 | if (add_front) |
| 142 | list_add(&rq->queuelist, &rq->q->queue_head); |
| 143 | else |
| 144 | list_add_tail(&rq->queuelist, &rq->q->queue_head); |
| 145 | return true; |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | /** |
| 150 | * blk_flush_complete_seq - complete flush sequence |
| 151 | * @rq: FLUSH/FUA request being sequenced |
| 152 | * @fq: flush queue |
| 153 | * @seq: sequences to complete (mask of %REQ_FSEQ_*, can be zero) |
| 154 | * @error: whether an error occurred |
| 155 | * |
| 156 | * @rq just completed @seq part of its flush sequence, record the |
| 157 | * completion and trigger the next step. |
| 158 | * |
| 159 | * CONTEXT: |
| 160 | * spin_lock_irq(q->queue_lock or fq->mq_flush_lock) |
| 161 | * |
| 162 | * RETURNS: |
| 163 | * %true if requests were added to the dispatch queue, %false otherwise. |
| 164 | */ |
| 165 | static bool blk_flush_complete_seq(struct request *rq, |
| 166 | struct blk_flush_queue *fq, |
| 167 | unsigned int seq, int error) |
| 168 | { |
| 169 | struct request_queue *q = rq->q; |
| 170 | struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx]; |
| 171 | bool queued = false, kicked; |
| 172 | |
| 173 | BUG_ON(rq->flush.seq & seq); |
| 174 | rq->flush.seq |= seq; |
| 175 | |
| 176 | if (likely(!error)) |
| 177 | seq = blk_flush_cur_seq(rq); |
| 178 | else |
| 179 | seq = REQ_FSEQ_DONE; |
| 180 | |
| 181 | switch (seq) { |
| 182 | case REQ_FSEQ_PREFLUSH: |
| 183 | case REQ_FSEQ_POSTFLUSH: |
| 184 | /* queue for flush */ |
| 185 | if (list_empty(pending)) |
| 186 | fq->flush_pending_since = jiffies; |
| 187 | list_move_tail(&rq->flush.list, pending); |
| 188 | break; |
| 189 | |
| 190 | case REQ_FSEQ_DATA: |
| 191 | list_move_tail(&rq->flush.list, &fq->flush_data_in_flight); |
| 192 | queued = blk_flush_queue_rq(rq, true); |
| 193 | break; |
| 194 | |
| 195 | case REQ_FSEQ_DONE: |
| 196 | /* |
| 197 | * @rq was previously adjusted by blk_flush_issue() for |
| 198 | * flush sequencing and may already have gone through the |
| 199 | * flush data request completion path. Restore @rq for |
| 200 | * normal completion and end it. |
| 201 | */ |
| 202 | BUG_ON(!list_empty(&rq->queuelist)); |
| 203 | list_del_init(&rq->flush.list); |
| 204 | blk_flush_restore_request(rq); |
| 205 | if (q->mq_ops) |
| 206 | blk_mq_end_request(rq, error); |
| 207 | else |
| 208 | __blk_end_request_all(rq, error); |
| 209 | break; |
| 210 | |
| 211 | default: |
| 212 | BUG(); |
| 213 | } |
| 214 | |
| 215 | kicked = blk_kick_flush(q, fq); |
| 216 | return kicked | queued; |
| 217 | } |
| 218 | |
| 219 | static void flush_end_io(struct request *flush_rq, int error) |
| 220 | { |
| 221 | struct request_queue *q = flush_rq->q; |
| 222 | struct list_head *running; |
| 223 | bool queued = false; |
| 224 | struct request *rq, *n; |
| 225 | unsigned long flags = 0; |
| 226 | struct blk_flush_queue *fq = blk_get_flush_queue(q, flush_rq->mq_ctx); |
| 227 | |
| 228 | if (q->mq_ops) { |
| 229 | struct blk_mq_hw_ctx *hctx; |
| 230 | |
| 231 | /* release the tag's ownership to the req cloned from */ |
| 232 | spin_lock_irqsave(&fq->mq_flush_lock, flags); |
| 233 | hctx = blk_mq_map_queue(q, flush_rq->mq_ctx->cpu); |
| 234 | blk_mq_tag_set_rq(hctx, flush_rq->tag, fq->orig_rq); |
| 235 | flush_rq->tag = -1; |
| 236 | } |
| 237 | |
| 238 | running = &fq->flush_queue[fq->flush_running_idx]; |
| 239 | BUG_ON(fq->flush_pending_idx == fq->flush_running_idx); |
| 240 | |
| 241 | /* account completion of the flush request */ |
| 242 | fq->flush_running_idx ^= 1; |
| 243 | |
| 244 | if (!q->mq_ops) |
| 245 | elv_completed_request(q, flush_rq); |
| 246 | |
| 247 | /* and push the waiting requests to the next stage */ |
| 248 | list_for_each_entry_safe(rq, n, running, flush.list) { |
| 249 | unsigned int seq = blk_flush_cur_seq(rq); |
| 250 | |
| 251 | BUG_ON(seq != REQ_FSEQ_PREFLUSH && seq != REQ_FSEQ_POSTFLUSH); |
| 252 | queued |= blk_flush_complete_seq(rq, fq, seq, error); |
| 253 | } |
| 254 | |
| 255 | /* |
| 256 | * Kick the queue to avoid stall for two cases: |
| 257 | * 1. Moving a request silently to empty queue_head may stall the |
| 258 | * queue. |
| 259 | * 2. When flush request is running in non-queueable queue, the |
| 260 | * queue is hold. Restart the queue after flush request is finished |
| 261 | * to avoid stall. |
| 262 | * This function is called from request completion path and calling |
| 263 | * directly into request_fn may confuse the driver. Always use |
| 264 | * kblockd. |
| 265 | */ |
| 266 | if (queued || fq->flush_queue_delayed) { |
| 267 | WARN_ON(q->mq_ops); |
| 268 | blk_run_queue_async(q); |
| 269 | } |
| 270 | fq->flush_queue_delayed = 0; |
| 271 | if (q->mq_ops) |
| 272 | spin_unlock_irqrestore(&fq->mq_flush_lock, flags); |
| 273 | } |
| 274 | |
| 275 | /** |
| 276 | * blk_kick_flush - consider issuing flush request |
| 277 | * @q: request_queue being kicked |
| 278 | * @fq: flush queue |
| 279 | * |
| 280 | * Flush related states of @q have changed, consider issuing flush request. |
| 281 | * Please read the comment at the top of this file for more info. |
| 282 | * |
| 283 | * CONTEXT: |
| 284 | * spin_lock_irq(q->queue_lock or fq->mq_flush_lock) |
| 285 | * |
| 286 | * RETURNS: |
| 287 | * %true if flush was issued, %false otherwise. |
| 288 | */ |
| 289 | static bool blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq) |
| 290 | { |
| 291 | struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx]; |
| 292 | struct request *first_rq = |
| 293 | list_first_entry(pending, struct request, flush.list); |
| 294 | struct request *flush_rq = fq->flush_rq; |
| 295 | |
| 296 | /* C1 described at the top of this file */ |
| 297 | if (fq->flush_pending_idx != fq->flush_running_idx || list_empty(pending)) |
| 298 | return false; |
| 299 | |
| 300 | /* C2 and C3 |
| 301 | * |
| 302 | * For blk-mq + scheduling, we can risk having all driver tags |
| 303 | * assigned to empty flushes, and we deadlock if we are expecting |
| 304 | * other requests to make progress. Don't defer for that case. |
| 305 | */ |
| 306 | if (!list_empty(&fq->flush_data_in_flight) && |
| 307 | !(q->mq_ops && q->elevator) && |
| 308 | time_before(jiffies, |
| 309 | fq->flush_pending_since + FLUSH_PENDING_TIMEOUT)) |
| 310 | return false; |
| 311 | |
| 312 | /* |
| 313 | * Issue flush and toggle pending_idx. This makes pending_idx |
| 314 | * different from running_idx, which means flush is in flight. |
| 315 | */ |
| 316 | fq->flush_pending_idx ^= 1; |
| 317 | |
| 318 | blk_rq_init(q, flush_rq); |
| 319 | |
| 320 | /* |
| 321 | * Borrow tag from the first request since they can't |
| 322 | * be in flight at the same time. And acquire the tag's |
| 323 | * ownership for flush req. |
| 324 | */ |
| 325 | if (q->mq_ops) { |
| 326 | struct blk_mq_hw_ctx *hctx; |
| 327 | |
| 328 | flush_rq->mq_ctx = first_rq->mq_ctx; |
| 329 | flush_rq->tag = first_rq->tag; |
| 330 | fq->orig_rq = first_rq; |
| 331 | |
| 332 | hctx = blk_mq_map_queue(q, first_rq->mq_ctx->cpu); |
| 333 | blk_mq_tag_set_rq(hctx, first_rq->tag, flush_rq); |
| 334 | } |
| 335 | |
| 336 | flush_rq->cmd_flags = REQ_OP_FLUSH | REQ_PREFLUSH; |
| 337 | flush_rq->rq_flags |= RQF_FLUSH_SEQ; |
| 338 | flush_rq->rq_disk = first_rq->rq_disk; |
| 339 | flush_rq->end_io = flush_end_io; |
| 340 | |
| 341 | return blk_flush_queue_rq(flush_rq, false); |
| 342 | } |
| 343 | |
| 344 | static void flush_data_end_io(struct request *rq, int error) |
| 345 | { |
| 346 | struct request_queue *q = rq->q; |
| 347 | struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL); |
| 348 | |
| 349 | /* |
| 350 | * Updating q->in_flight[] here for making this tag usable |
| 351 | * early. Because in blk_queue_start_tag(), |
| 352 | * q->in_flight[BLK_RW_ASYNC] is used to limit async I/O and |
| 353 | * reserve tags for sync I/O. |
| 354 | * |
| 355 | * More importantly this way can avoid the following I/O |
| 356 | * deadlock: |
| 357 | * |
| 358 | * - suppose there are 40 fua requests comming to flush queue |
| 359 | * and queue depth is 31 |
| 360 | * - 30 rqs are scheduled then blk_queue_start_tag() can't alloc |
| 361 | * tag for async I/O any more |
| 362 | * - all the 30 rqs are completed before FLUSH_PENDING_TIMEOUT |
| 363 | * and flush_data_end_io() is called |
| 364 | * - the other rqs still can't go ahead if not updating |
| 365 | * q->in_flight[BLK_RW_ASYNC] here, meantime these rqs |
| 366 | * are held in flush data queue and make no progress of |
| 367 | * handling post flush rq |
| 368 | * - only after the post flush rq is handled, all these rqs |
| 369 | * can be completed |
| 370 | */ |
| 371 | |
| 372 | elv_completed_request(q, rq); |
| 373 | |
| 374 | /* for avoiding double accounting */ |
| 375 | rq->rq_flags &= ~RQF_STARTED; |
| 376 | |
| 377 | /* |
| 378 | * After populating an empty queue, kick it to avoid stall. Read |
| 379 | * the comment in flush_end_io(). |
| 380 | */ |
| 381 | if (blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error)) |
| 382 | blk_run_queue_async(q); |
| 383 | } |
| 384 | |
| 385 | static void mq_flush_data_end_io(struct request *rq, int error) |
| 386 | { |
| 387 | struct request_queue *q = rq->q; |
| 388 | struct blk_mq_hw_ctx *hctx; |
| 389 | struct blk_mq_ctx *ctx = rq->mq_ctx; |
| 390 | unsigned long flags; |
| 391 | struct blk_flush_queue *fq = blk_get_flush_queue(q, ctx); |
| 392 | |
| 393 | hctx = blk_mq_map_queue(q, ctx->cpu); |
| 394 | |
| 395 | /* |
| 396 | * After populating an empty queue, kick it to avoid stall. Read |
| 397 | * the comment in flush_end_io(). |
| 398 | */ |
| 399 | spin_lock_irqsave(&fq->mq_flush_lock, flags); |
| 400 | blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error); |
| 401 | spin_unlock_irqrestore(&fq->mq_flush_lock, flags); |
| 402 | |
| 403 | blk_mq_run_hw_queue(hctx, true); |
| 404 | } |
| 405 | |
| 406 | /** |
| 407 | * blk_insert_flush - insert a new FLUSH/FUA request |
| 408 | * @rq: request to insert |
| 409 | * |
| 410 | * To be called from __elv_add_request() for %ELEVATOR_INSERT_FLUSH insertions. |
| 411 | * or __blk_mq_run_hw_queue() to dispatch request. |
| 412 | * @rq is being submitted. Analyze what needs to be done and put it on the |
| 413 | * right queue. |
| 414 | * |
| 415 | * CONTEXT: |
| 416 | * spin_lock_irq(q->queue_lock) in !mq case |
| 417 | */ |
| 418 | void blk_insert_flush(struct request *rq) |
| 419 | { |
| 420 | struct request_queue *q = rq->q; |
| 421 | unsigned long fflags = q->queue_flags; /* may change, cache */ |
| 422 | unsigned int policy = blk_flush_policy(fflags, rq); |
| 423 | struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx); |
| 424 | |
| 425 | /* |
| 426 | * @policy now records what operations need to be done. Adjust |
| 427 | * REQ_PREFLUSH and FUA for the driver. |
| 428 | */ |
| 429 | rq->cmd_flags &= ~REQ_PREFLUSH; |
| 430 | if (!(fflags & (1UL << QUEUE_FLAG_FUA))) |
| 431 | rq->cmd_flags &= ~REQ_FUA; |
| 432 | |
| 433 | /* |
| 434 | * REQ_PREFLUSH|REQ_FUA implies REQ_SYNC, so if we clear any |
| 435 | * of those flags, we have to set REQ_SYNC to avoid skewing |
| 436 | * the request accounting. |
| 437 | */ |
| 438 | rq->cmd_flags |= REQ_SYNC; |
| 439 | |
| 440 | /* |
| 441 | * An empty flush handed down from a stacking driver may |
| 442 | * translate into nothing if the underlying device does not |
| 443 | * advertise a write-back cache. In this case, simply |
| 444 | * complete the request. |
| 445 | */ |
| 446 | if (!policy) { |
| 447 | if (q->mq_ops) |
| 448 | blk_mq_end_request(rq, 0); |
| 449 | else |
| 450 | __blk_end_request(rq, 0, 0); |
| 451 | return; |
| 452 | } |
| 453 | |
| 454 | BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */ |
| 455 | |
| 456 | /* |
| 457 | * If there's data but flush is not necessary, the request can be |
| 458 | * processed directly without going through flush machinery. Queue |
| 459 | * for normal execution. |
| 460 | */ |
| 461 | if ((policy & REQ_FSEQ_DATA) && |
| 462 | !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) { |
| 463 | if (q->mq_ops) |
| 464 | blk_mq_sched_insert_request(rq, false, true, false, false); |
| 465 | else |
| 466 | list_add_tail(&rq->queuelist, &q->queue_head); |
| 467 | return; |
| 468 | } |
| 469 | |
| 470 | /* |
| 471 | * @rq should go through flush machinery. Mark it part of flush |
| 472 | * sequence and submit for further processing. |
| 473 | */ |
| 474 | memset(&rq->flush, 0, sizeof(rq->flush)); |
| 475 | INIT_LIST_HEAD(&rq->flush.list); |
| 476 | rq->rq_flags |= RQF_FLUSH_SEQ; |
| 477 | rq->flush.saved_end_io = rq->end_io; /* Usually NULL */ |
| 478 | if (q->mq_ops) { |
| 479 | rq->end_io = mq_flush_data_end_io; |
| 480 | |
| 481 | spin_lock_irq(&fq->mq_flush_lock); |
| 482 | blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0); |
| 483 | spin_unlock_irq(&fq->mq_flush_lock); |
| 484 | return; |
| 485 | } |
| 486 | rq->end_io = flush_data_end_io; |
| 487 | |
| 488 | blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0); |
| 489 | } |
| 490 | |
| 491 | /** |
| 492 | * blkdev_issue_flush - queue a flush |
| 493 | * @bdev: blockdev to issue flush for |
| 494 | * @gfp_mask: memory allocation flags (for bio_alloc) |
| 495 | * @error_sector: error sector |
| 496 | * |
| 497 | * Description: |
| 498 | * Issue a flush for the block device in question. Caller can supply |
| 499 | * room for storing the error offset in case of a flush error, if they |
| 500 | * wish to. |
| 501 | */ |
| 502 | int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask, |
| 503 | sector_t *error_sector) |
| 504 | { |
| 505 | struct request_queue *q; |
| 506 | struct bio *bio; |
| 507 | int ret = 0; |
| 508 | |
| 509 | if (bdev->bd_disk == NULL) |
| 510 | return -ENXIO; |
| 511 | |
| 512 | q = bdev_get_queue(bdev); |
| 513 | if (!q) |
| 514 | return -ENXIO; |
| 515 | |
| 516 | /* |
| 517 | * some block devices may not have their queue correctly set up here |
| 518 | * (e.g. loop device without a backing file) and so issuing a flush |
| 519 | * here will panic. Ensure there is a request function before issuing |
| 520 | * the flush. |
| 521 | */ |
| 522 | if (!q->make_request_fn) |
| 523 | return -ENXIO; |
| 524 | |
| 525 | bio = bio_alloc(gfp_mask, 0); |
| 526 | bio->bi_bdev = bdev; |
| 527 | bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH; |
| 528 | |
| 529 | ret = submit_bio_wait(bio); |
| 530 | |
| 531 | /* |
| 532 | * The driver must store the error location in ->bi_sector, if |
| 533 | * it supports it. For non-stacked drivers, this should be |
| 534 | * copied from blk_rq_pos(rq). |
| 535 | */ |
| 536 | if (error_sector) |
| 537 | *error_sector = bio->bi_iter.bi_sector; |
| 538 | |
| 539 | bio_put(bio); |
| 540 | return ret; |
| 541 | } |
| 542 | EXPORT_SYMBOL(blkdev_issue_flush); |
| 543 | |
| 544 | struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q, |
| 545 | int node, int cmd_size) |
| 546 | { |
| 547 | struct blk_flush_queue *fq; |
| 548 | int rq_sz = sizeof(struct request); |
| 549 | |
| 550 | fq = kzalloc_node(sizeof(*fq), GFP_KERNEL, node); |
| 551 | if (!fq) |
| 552 | goto fail; |
| 553 | |
| 554 | if (q->mq_ops) |
| 555 | spin_lock_init(&fq->mq_flush_lock); |
| 556 | |
| 557 | rq_sz = round_up(rq_sz + cmd_size, cache_line_size()); |
| 558 | fq->flush_rq = kzalloc_node(rq_sz, GFP_KERNEL, node); |
| 559 | if (!fq->flush_rq) |
| 560 | goto fail_rq; |
| 561 | |
| 562 | INIT_LIST_HEAD(&fq->flush_queue[0]); |
| 563 | INIT_LIST_HEAD(&fq->flush_queue[1]); |
| 564 | INIT_LIST_HEAD(&fq->flush_data_in_flight); |
| 565 | |
| 566 | return fq; |
| 567 | |
| 568 | fail_rq: |
| 569 | kfree(fq); |
| 570 | fail: |
| 571 | return NULL; |
| 572 | } |
| 573 | |
| 574 | void blk_free_flush_queue(struct blk_flush_queue *fq) |
| 575 | { |
| 576 | /* bio based request queue hasn't flush queue */ |
| 577 | if (!fq) |
| 578 | return; |
| 579 | |
| 580 | kfree(fq->flush_rq); |
| 581 | kfree(fq); |
| 582 | } |