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86db1e29 | 1 | /* |
4fed947c | 2 | * Functions to sequence FLUSH and FUA writes. |
ae1b1539 TH |
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_FLUSH makes sense, which | |
14 | * indicates a simple flush request. If there is data, REQ_FLUSH 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_FLUSH 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_FLUSH is | |
27 | * 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 | * q->flush_queue[q->flush_pending_idx]. Once certain criteria are met, a | |
32 | * 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 REQ_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. | |
86db1e29 | 65 | */ |
ae1b1539 | 66 | |
86db1e29 JA |
67 | #include <linux/kernel.h> |
68 | #include <linux/module.h> | |
69 | #include <linux/bio.h> | |
70 | #include <linux/blkdev.h> | |
5a0e3ad6 | 71 | #include <linux/gfp.h> |
320ae51f | 72 | #include <linux/blk-mq.h> |
86db1e29 JA |
73 | |
74 | #include "blk.h" | |
320ae51f | 75 | #include "blk-mq.h" |
86db1e29 | 76 | |
4fed947c TH |
77 | /* FLUSH/FUA sequences */ |
78 | enum { | |
ae1b1539 TH |
79 | REQ_FSEQ_PREFLUSH = (1 << 0), /* pre-flushing in progress */ |
80 | REQ_FSEQ_DATA = (1 << 1), /* data write in progress */ | |
81 | REQ_FSEQ_POSTFLUSH = (1 << 2), /* post-flushing in progress */ | |
82 | REQ_FSEQ_DONE = (1 << 3), | |
83 | ||
84 | REQ_FSEQ_ACTIONS = REQ_FSEQ_PREFLUSH | REQ_FSEQ_DATA | | |
85 | REQ_FSEQ_POSTFLUSH, | |
86 | ||
87 | /* | |
88 | * If flush has been pending longer than the following timeout, | |
89 | * it's issued even if flush_data requests are still in flight. | |
90 | */ | |
91 | FLUSH_PENDING_TIMEOUT = 5 * HZ, | |
4fed947c TH |
92 | }; |
93 | ||
ae1b1539 | 94 | static bool blk_kick_flush(struct request_queue *q); |
28e7d184 | 95 | |
ae1b1539 | 96 | static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq) |
86db1e29 | 97 | { |
ae1b1539 | 98 | unsigned int policy = 0; |
86db1e29 | 99 | |
fa1bf42f JM |
100 | if (blk_rq_sectors(rq)) |
101 | policy |= REQ_FSEQ_DATA; | |
102 | ||
ae1b1539 TH |
103 | if (fflags & REQ_FLUSH) { |
104 | if (rq->cmd_flags & REQ_FLUSH) | |
105 | policy |= REQ_FSEQ_PREFLUSH; | |
ae1b1539 TH |
106 | if (!(fflags & REQ_FUA) && (rq->cmd_flags & REQ_FUA)) |
107 | policy |= REQ_FSEQ_POSTFLUSH; | |
28e7d184 | 108 | } |
ae1b1539 | 109 | return policy; |
86db1e29 JA |
110 | } |
111 | ||
ae1b1539 | 112 | static unsigned int blk_flush_cur_seq(struct request *rq) |
47f70d5a | 113 | { |
ae1b1539 TH |
114 | return 1 << ffz(rq->flush.seq); |
115 | } | |
47f70d5a | 116 | |
ae1b1539 TH |
117 | static void blk_flush_restore_request(struct request *rq) |
118 | { | |
47f70d5a | 119 | /* |
ae1b1539 TH |
120 | * After flush data completion, @rq->bio is %NULL but we need to |
121 | * complete the bio again. @rq->biotail is guaranteed to equal the | |
122 | * original @rq->bio. Restore it. | |
47f70d5a | 123 | */ |
ae1b1539 TH |
124 | rq->bio = rq->biotail; |
125 | ||
126 | /* make @rq a normal request */ | |
127 | rq->cmd_flags &= ~REQ_FLUSH_SEQ; | |
4853abaa | 128 | rq->end_io = rq->flush.saved_end_io; |
320ae51f JA |
129 | |
130 | blk_clear_rq_complete(rq); | |
131 | } | |
132 | ||
10beafc1 | 133 | static bool blk_flush_queue_rq(struct request *rq, bool add_front) |
320ae51f | 134 | { |
18741986 | 135 | if (rq->q->mq_ops) { |
6fca6a61 CH |
136 | struct request_queue *q = rq->q; |
137 | ||
138 | blk_mq_add_to_requeue_list(rq, add_front); | |
139 | blk_mq_kick_requeue_list(q); | |
18741986 CH |
140 | return false; |
141 | } else { | |
10beafc1 MS |
142 | if (add_front) |
143 | list_add(&rq->queuelist, &rq->q->queue_head); | |
144 | else | |
145 | list_add_tail(&rq->queuelist, &rq->q->queue_head); | |
18741986 CH |
146 | return true; |
147 | } | |
47f70d5a TH |
148 | } |
149 | ||
ae1b1539 TH |
150 | /** |
151 | * blk_flush_complete_seq - complete flush sequence | |
152 | * @rq: FLUSH/FUA request being sequenced | |
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: | |
320ae51f | 160 | * spin_lock_irq(q->queue_lock or q->mq_flush_lock) |
ae1b1539 TH |
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, unsigned int seq, | |
166 | int error) | |
86db1e29 | 167 | { |
ae1b1539 TH |
168 | struct request_queue *q = rq->q; |
169 | struct list_head *pending = &q->flush_queue[q->flush_pending_idx]; | |
320ae51f | 170 | bool queued = false, kicked; |
ae1b1539 TH |
171 | |
172 | BUG_ON(rq->flush.seq & seq); | |
173 | rq->flush.seq |= seq; | |
174 | ||
175 | if (likely(!error)) | |
176 | seq = blk_flush_cur_seq(rq); | |
177 | else | |
178 | seq = REQ_FSEQ_DONE; | |
179 | ||
180 | switch (seq) { | |
181 | case REQ_FSEQ_PREFLUSH: | |
182 | case REQ_FSEQ_POSTFLUSH: | |
183 | /* queue for flush */ | |
184 | if (list_empty(pending)) | |
185 | q->flush_pending_since = jiffies; | |
186 | list_move_tail(&rq->flush.list, pending); | |
187 | break; | |
188 | ||
189 | case REQ_FSEQ_DATA: | |
190 | list_move_tail(&rq->flush.list, &q->flush_data_in_flight); | |
10beafc1 | 191 | queued = blk_flush_queue_rq(rq, true); |
ae1b1539 TH |
192 | break; |
193 | ||
194 | case REQ_FSEQ_DONE: | |
195 | /* | |
196 | * @rq was previously adjusted by blk_flush_issue() for | |
197 | * flush sequencing and may already have gone through the | |
198 | * flush data request completion path. Restore @rq for | |
199 | * normal completion and end it. | |
200 | */ | |
201 | BUG_ON(!list_empty(&rq->queuelist)); | |
202 | list_del_init(&rq->flush.list); | |
203 | blk_flush_restore_request(rq); | |
320ae51f JA |
204 | if (q->mq_ops) |
205 | blk_mq_end_io(rq, error); | |
206 | else | |
207 | __blk_end_request_all(rq, error); | |
ae1b1539 TH |
208 | break; |
209 | ||
210 | default: | |
211 | BUG(); | |
212 | } | |
213 | ||
320ae51f | 214 | kicked = blk_kick_flush(q); |
320ae51f | 215 | return kicked | queued; |
86db1e29 JA |
216 | } |
217 | ||
ae1b1539 | 218 | static void flush_end_io(struct request *flush_rq, int error) |
86db1e29 | 219 | { |
ae1b1539 | 220 | struct request_queue *q = flush_rq->q; |
320ae51f | 221 | struct list_head *running; |
ae1b1539 TH |
222 | bool queued = false; |
223 | struct request *rq, *n; | |
320ae51f | 224 | unsigned long flags = 0; |
ae1b1539 | 225 | |
22302375 | 226 | if (q->mq_ops) { |
320ae51f | 227 | spin_lock_irqsave(&q->mq_flush_lock, flags); |
22302375 SL |
228 | q->flush_rq->cmd_flags = 0; |
229 | } | |
18741986 | 230 | |
320ae51f | 231 | running = &q->flush_queue[q->flush_running_idx]; |
ae1b1539 TH |
232 | BUG_ON(q->flush_pending_idx == q->flush_running_idx); |
233 | ||
234 | /* account completion of the flush request */ | |
235 | q->flush_running_idx ^= 1; | |
320ae51f JA |
236 | |
237 | if (!q->mq_ops) | |
238 | elv_completed_request(q, flush_rq); | |
ae1b1539 TH |
239 | |
240 | /* and push the waiting requests to the next stage */ | |
241 | list_for_each_entry_safe(rq, n, running, flush.list) { | |
242 | unsigned int seq = blk_flush_cur_seq(rq); | |
243 | ||
244 | BUG_ON(seq != REQ_FSEQ_PREFLUSH && seq != REQ_FSEQ_POSTFLUSH); | |
245 | queued |= blk_flush_complete_seq(rq, seq, error); | |
246 | } | |
247 | ||
47f70d5a | 248 | /* |
3ac0cc45 | 249 | * Kick the queue to avoid stall for two cases: |
250 | * 1. Moving a request silently to empty queue_head may stall the | |
251 | * queue. | |
252 | * 2. When flush request is running in non-queueable queue, the | |
253 | * queue is hold. Restart the queue after flush request is finished | |
254 | * to avoid stall. | |
255 | * This function is called from request completion path and calling | |
256 | * directly into request_fn may confuse the driver. Always use | |
257 | * kblockd. | |
47f70d5a | 258 | */ |
320ae51f | 259 | if (queued || q->flush_queue_delayed) { |
18741986 CH |
260 | WARN_ON(q->mq_ops); |
261 | blk_run_queue_async(q); | |
320ae51f | 262 | } |
3ac0cc45 | 263 | q->flush_queue_delayed = 0; |
320ae51f JA |
264 | if (q->mq_ops) |
265 | spin_unlock_irqrestore(&q->mq_flush_lock, flags); | |
266 | } | |
267 | ||
ae1b1539 TH |
268 | /** |
269 | * blk_kick_flush - consider issuing flush request | |
270 | * @q: request_queue being kicked | |
271 | * | |
272 | * Flush related states of @q have changed, consider issuing flush request. | |
273 | * Please read the comment at the top of this file for more info. | |
274 | * | |
275 | * CONTEXT: | |
320ae51f | 276 | * spin_lock_irq(q->queue_lock or q->mq_flush_lock) |
ae1b1539 TH |
277 | * |
278 | * RETURNS: | |
279 | * %true if flush was issued, %false otherwise. | |
280 | */ | |
281 | static bool blk_kick_flush(struct request_queue *q) | |
86db1e29 | 282 | { |
ae1b1539 TH |
283 | struct list_head *pending = &q->flush_queue[q->flush_pending_idx]; |
284 | struct request *first_rq = | |
285 | list_first_entry(pending, struct request, flush.list); | |
286 | ||
287 | /* C1 described at the top of this file */ | |
288 | if (q->flush_pending_idx != q->flush_running_idx || list_empty(pending)) | |
289 | return false; | |
290 | ||
291 | /* C2 and C3 */ | |
292 | if (!list_empty(&q->flush_data_in_flight) && | |
293 | time_before(jiffies, | |
294 | q->flush_pending_since + FLUSH_PENDING_TIMEOUT)) | |
295 | return false; | |
296 | ||
297 | /* | |
298 | * Issue flush and toggle pending_idx. This makes pending_idx | |
299 | * different from running_idx, which means flush is in flight. | |
300 | */ | |
320ae51f | 301 | q->flush_pending_idx ^= 1; |
18741986 | 302 | |
9d74e257 | 303 | blk_rq_init(q, q->flush_rq); |
8727af4b CH |
304 | if (q->mq_ops) |
305 | blk_mq_clone_flush_request(q->flush_rq, first_rq); | |
320ae51f | 306 | |
18741986 CH |
307 | q->flush_rq->cmd_type = REQ_TYPE_FS; |
308 | q->flush_rq->cmd_flags = WRITE_FLUSH | REQ_FLUSH_SEQ; | |
309 | q->flush_rq->rq_disk = first_rq->rq_disk; | |
310 | q->flush_rq->end_io = flush_end_io; | |
ae1b1539 | 311 | |
10beafc1 | 312 | return blk_flush_queue_rq(q->flush_rq, false); |
86db1e29 JA |
313 | } |
314 | ||
ae1b1539 | 315 | static void flush_data_end_io(struct request *rq, int error) |
86db1e29 | 316 | { |
ae1b1539 | 317 | struct request_queue *q = rq->q; |
ae1b1539 | 318 | |
e83a46bb TH |
319 | /* |
320 | * After populating an empty queue, kick it to avoid stall. Read | |
321 | * the comment in flush_end_io(). | |
322 | */ | |
73c10101 | 323 | if (blk_flush_complete_seq(rq, REQ_FSEQ_DATA, error)) |
24ecfbe2 | 324 | blk_run_queue_async(q); |
86db1e29 JA |
325 | } |
326 | ||
320ae51f JA |
327 | static void mq_flush_data_end_io(struct request *rq, int error) |
328 | { | |
329 | struct request_queue *q = rq->q; | |
330 | struct blk_mq_hw_ctx *hctx; | |
331 | struct blk_mq_ctx *ctx; | |
332 | unsigned long flags; | |
333 | ||
334 | ctx = rq->mq_ctx; | |
335 | hctx = q->mq_ops->map_queue(q, ctx->cpu); | |
336 | ||
337 | /* | |
338 | * After populating an empty queue, kick it to avoid stall. Read | |
339 | * the comment in flush_end_io(). | |
340 | */ | |
341 | spin_lock_irqsave(&q->mq_flush_lock, flags); | |
342 | if (blk_flush_complete_seq(rq, REQ_FSEQ_DATA, error)) | |
343 | blk_mq_run_hw_queue(hctx, true); | |
344 | spin_unlock_irqrestore(&q->mq_flush_lock, flags); | |
345 | } | |
346 | ||
ae1b1539 TH |
347 | /** |
348 | * blk_insert_flush - insert a new FLUSH/FUA request | |
349 | * @rq: request to insert | |
350 | * | |
b710a480 | 351 | * To be called from __elv_add_request() for %ELEVATOR_INSERT_FLUSH insertions. |
320ae51f | 352 | * or __blk_mq_run_hw_queue() to dispatch request. |
ae1b1539 TH |
353 | * @rq is being submitted. Analyze what needs to be done and put it on the |
354 | * right queue. | |
355 | * | |
356 | * CONTEXT: | |
320ae51f | 357 | * spin_lock_irq(q->queue_lock) in !mq case |
ae1b1539 TH |
358 | */ |
359 | void blk_insert_flush(struct request *rq) | |
86db1e29 | 360 | { |
ae1b1539 TH |
361 | struct request_queue *q = rq->q; |
362 | unsigned int fflags = q->flush_flags; /* may change, cache */ | |
363 | unsigned int policy = blk_flush_policy(fflags, rq); | |
86db1e29 | 364 | |
ae1b1539 TH |
365 | /* |
366 | * @policy now records what operations need to be done. Adjust | |
367 | * REQ_FLUSH and FUA for the driver. | |
368 | */ | |
18741986 | 369 | rq->cmd_flags &= ~REQ_FLUSH; |
ae1b1539 TH |
370 | if (!(fflags & REQ_FUA)) |
371 | rq->cmd_flags &= ~REQ_FUA; | |
372 | ||
4853abaa JM |
373 | /* |
374 | * An empty flush handed down from a stacking driver may | |
375 | * translate into nothing if the underlying device does not | |
376 | * advertise a write-back cache. In this case, simply | |
377 | * complete the request. | |
378 | */ | |
379 | if (!policy) { | |
320ae51f JA |
380 | if (q->mq_ops) |
381 | blk_mq_end_io(rq, 0); | |
382 | else | |
383 | __blk_end_bidi_request(rq, 0, 0, 0); | |
4853abaa JM |
384 | return; |
385 | } | |
386 | ||
834f9f61 | 387 | BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */ |
4853abaa | 388 | |
ae1b1539 TH |
389 | /* |
390 | * If there's data but flush is not necessary, the request can be | |
391 | * processed directly without going through flush machinery. Queue | |
392 | * for normal execution. | |
393 | */ | |
394 | if ((policy & REQ_FSEQ_DATA) && | |
395 | !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) { | |
320ae51f | 396 | if (q->mq_ops) { |
feb71dae | 397 | blk_mq_insert_request(rq, false, false, true); |
320ae51f JA |
398 | } else |
399 | list_add_tail(&rq->queuelist, &q->queue_head); | |
ae1b1539 | 400 | return; |
28e7d184 | 401 | } |
cde4c406 | 402 | |
ae1b1539 TH |
403 | /* |
404 | * @rq should go through flush machinery. Mark it part of flush | |
405 | * sequence and submit for further processing. | |
406 | */ | |
407 | memset(&rq->flush, 0, sizeof(rq->flush)); | |
408 | INIT_LIST_HEAD(&rq->flush.list); | |
414b4ff5 | 409 | rq->cmd_flags |= REQ_FLUSH_SEQ; |
4853abaa | 410 | rq->flush.saved_end_io = rq->end_io; /* Usually NULL */ |
320ae51f JA |
411 | if (q->mq_ops) { |
412 | rq->end_io = mq_flush_data_end_io; | |
413 | ||
414 | spin_lock_irq(&q->mq_flush_lock); | |
415 | blk_flush_complete_seq(rq, REQ_FSEQ_ACTIONS & ~policy, 0); | |
416 | spin_unlock_irq(&q->mq_flush_lock); | |
417 | return; | |
418 | } | |
ae1b1539 TH |
419 | rq->end_io = flush_data_end_io; |
420 | ||
421 | blk_flush_complete_seq(rq, REQ_FSEQ_ACTIONS & ~policy, 0); | |
86db1e29 JA |
422 | } |
423 | ||
ae1b1539 TH |
424 | /** |
425 | * blk_abort_flushes - @q is being aborted, abort flush requests | |
426 | * @q: request_queue being aborted | |
427 | * | |
428 | * To be called from elv_abort_queue(). @q is being aborted. Prepare all | |
429 | * FLUSH/FUA requests for abortion. | |
430 | * | |
431 | * CONTEXT: | |
432 | * spin_lock_irq(q->queue_lock) | |
433 | */ | |
434 | void blk_abort_flushes(struct request_queue *q) | |
86db1e29 | 435 | { |
ae1b1539 TH |
436 | struct request *rq, *n; |
437 | int i; | |
28e7d184 | 438 | |
4fed947c | 439 | /* |
ae1b1539 TH |
440 | * Requests in flight for data are already owned by the dispatch |
441 | * queue or the device driver. Just restore for normal completion. | |
4fed947c | 442 | */ |
ae1b1539 TH |
443 | list_for_each_entry_safe(rq, n, &q->flush_data_in_flight, flush.list) { |
444 | list_del_init(&rq->flush.list); | |
445 | blk_flush_restore_request(rq); | |
4fed947c | 446 | } |
28e7d184 | 447 | |
4fed947c | 448 | /* |
ae1b1539 TH |
449 | * We need to give away requests on flush queues. Restore for |
450 | * normal completion and put them on the dispatch queue. | |
4fed947c | 451 | */ |
ae1b1539 TH |
452 | for (i = 0; i < ARRAY_SIZE(q->flush_queue); i++) { |
453 | list_for_each_entry_safe(rq, n, &q->flush_queue[i], | |
454 | flush.list) { | |
455 | list_del_init(&rq->flush.list); | |
456 | blk_flush_restore_request(rq); | |
457 | list_add_tail(&rq->queuelist, &q->queue_head); | |
458 | } | |
28e7d184 | 459 | } |
86db1e29 JA |
460 | } |
461 | ||
86db1e29 JA |
462 | /** |
463 | * blkdev_issue_flush - queue a flush | |
464 | * @bdev: blockdev to issue flush for | |
fbd9b09a | 465 | * @gfp_mask: memory allocation flags (for bio_alloc) |
86db1e29 JA |
466 | * @error_sector: error sector |
467 | * | |
468 | * Description: | |
469 | * Issue a flush for the block device in question. Caller can supply | |
470 | * room for storing the error offset in case of a flush error, if they | |
f17e232e DM |
471 | * wish to. If WAIT flag is not passed then caller may check only what |
472 | * request was pushed in some internal queue for later handling. | |
86db1e29 | 473 | */ |
fbd9b09a | 474 | int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask, |
dd3932ed | 475 | sector_t *error_sector) |
86db1e29 | 476 | { |
86db1e29 JA |
477 | struct request_queue *q; |
478 | struct bio *bio; | |
fbd9b09a | 479 | int ret = 0; |
86db1e29 JA |
480 | |
481 | if (bdev->bd_disk == NULL) | |
482 | return -ENXIO; | |
483 | ||
484 | q = bdev_get_queue(bdev); | |
485 | if (!q) | |
486 | return -ENXIO; | |
487 | ||
f10d9f61 DC |
488 | /* |
489 | * some block devices may not have their queue correctly set up here | |
490 | * (e.g. loop device without a backing file) and so issuing a flush | |
491 | * here will panic. Ensure there is a request function before issuing | |
d391a2dd | 492 | * the flush. |
f10d9f61 DC |
493 | */ |
494 | if (!q->make_request_fn) | |
495 | return -ENXIO; | |
496 | ||
fbd9b09a | 497 | bio = bio_alloc(gfp_mask, 0); |
86db1e29 | 498 | bio->bi_bdev = bdev; |
86db1e29 | 499 | |
33879d45 | 500 | ret = submit_bio_wait(WRITE_FLUSH, bio); |
dd3932ed CH |
501 | |
502 | /* | |
503 | * The driver must store the error location in ->bi_sector, if | |
504 | * it supports it. For non-stacked drivers, this should be | |
505 | * copied from blk_rq_pos(rq). | |
506 | */ | |
507 | if (error_sector) | |
4f024f37 | 508 | *error_sector = bio->bi_iter.bi_sector; |
86db1e29 | 509 | |
86db1e29 JA |
510 | bio_put(bio); |
511 | return ret; | |
512 | } | |
86db1e29 | 513 | EXPORT_SYMBOL(blkdev_issue_flush); |
320ae51f JA |
514 | |
515 | void blk_mq_init_flush(struct request_queue *q) | |
516 | { | |
517 | spin_lock_init(&q->mq_flush_lock); | |
320ae51f | 518 | } |