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Jens Axboe86db1e22008-01-29 14:53:40 +01001/*
Tejun Heo4fed9472010-09-03 11:56:17 +02002 * Functions to sequence FLUSH and FUA writes.
Tejun Heoae1b1532011-01-25 12:43:54 +01003 *
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.
Jens Axboe86db1e22008-01-29 14:53:40 +010065 */
Tejun Heoae1b1532011-01-25 12:43:54 +010066
Jens Axboe86db1e22008-01-29 14:53:40 +010067#include <linux/kernel.h>
68#include <linux/module.h>
69#include <linux/bio.h>
70#include <linux/blkdev.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090071#include <linux/gfp.h>
Jens Axboe320ae512013-10-24 09:20:05 +010072#include <linux/blk-mq.h>
Jens Axboe86db1e22008-01-29 14:53:40 +010073
74#include "blk.h"
Jens Axboe320ae512013-10-24 09:20:05 +010075#include "blk-mq.h"
Jens Axboe86db1e22008-01-29 14:53:40 +010076
Tejun Heo4fed9472010-09-03 11:56:17 +020077/* FLUSH/FUA sequences */
78enum {
Tejun Heoae1b1532011-01-25 12:43:54 +010079 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),
Tejun Heo4fed9472010-09-03 11:56:17 +020083
Tejun Heoae1b1532011-01-25 12:43:54 +010084 REQ_FSEQ_ACTIONS = REQ_FSEQ_PREFLUSH | REQ_FSEQ_DATA |
85 REQ_FSEQ_POSTFLUSH,
Tejun Heo47f70d52010-09-03 11:56:17 +020086
87 /*
Tejun Heoae1b1532011-01-25 12:43:54 +010088 * If flush has been pending longer than the following timeout,
89 * it's issued even if flush_data requests are still in flight.
Tejun Heo47f70d52010-09-03 11:56:17 +020090 */
Tejun Heoae1b1532011-01-25 12:43:54 +010091 FLUSH_PENDING_TIMEOUT = 5 * HZ,
92};
93
94static bool blk_kick_flush(struct request_queue *q);
95
96static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq)
97{
98 unsigned int policy = 0;
99
Jeff Moyerfa1bf422011-08-09 20:32:09 +0200100 if (blk_rq_sectors(rq))
101 policy |= REQ_FSEQ_DATA;
102
Tejun Heoae1b1532011-01-25 12:43:54 +0100103 if (fflags & REQ_FLUSH) {
104 if (rq->cmd_flags & REQ_FLUSH)
105 policy |= REQ_FSEQ_PREFLUSH;
Tejun Heoae1b1532011-01-25 12:43:54 +0100106 if (!(fflags & REQ_FUA) && (rq->cmd_flags & REQ_FUA))
107 policy |= REQ_FSEQ_POSTFLUSH;
108 }
109 return policy;
Tejun Heo47f70d52010-09-03 11:56:17 +0200110}
111
Tejun Heoae1b1532011-01-25 12:43:54 +0100112static unsigned int blk_flush_cur_seq(struct request *rq)
Jens Axboe86db1e22008-01-29 14:53:40 +0100113{
Tejun Heoae1b1532011-01-25 12:43:54 +0100114 return 1 << ffz(rq->flush.seq);
Jens Axboe86db1e22008-01-29 14:53:40 +0100115}
116
Tejun Heoae1b1532011-01-25 12:43:54 +0100117static void blk_flush_restore_request(struct request *rq)
Jens Axboe86db1e22008-01-29 14:53:40 +0100118{
Tejun Heoae1b1532011-01-25 12:43:54 +0100119 /*
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.
123 */
124 rq->bio = rq->biotail;
125
126 /* make @rq a normal request */
127 rq->cmd_flags &= ~REQ_FLUSH_SEQ;
Jeff Moyer4853aba2011-08-15 21:37:25 +0200128 rq->end_io = rq->flush.saved_end_io;
Jens Axboe320ae512013-10-24 09:20:05 +0100129
130 blk_clear_rq_complete(rq);
131}
132
Mike Snitzer10beafc2014-03-08 20:19:20 -0700133static bool blk_flush_queue_rq(struct request *rq, bool add_front)
Jens Axboe320ae512013-10-24 09:20:05 +0100134{
Christoph Hellwig18741982014-02-10 09:29:00 -0700135 if (rq->q->mq_ops) {
Christoph Hellwig6fca6a62014-05-28 08:08:02 -0600136 struct request_queue *q = rq->q;
137
138 blk_mq_add_to_requeue_list(rq, add_front);
139 blk_mq_kick_requeue_list(q);
Christoph Hellwig18741982014-02-10 09:29:00 -0700140 return false;
141 } else {
Mike Snitzer10beafc2014-03-08 20:19:20 -0700142 if (add_front)
143 list_add(&rq->queuelist, &rq->q->queue_head);
144 else
145 list_add_tail(&rq->queuelist, &rq->q->queue_head);
Christoph Hellwig18741982014-02-10 09:29:00 -0700146 return true;
147 }
Jens Axboe86db1e22008-01-29 14:53:40 +0100148}
149
Tejun Heoae1b1532011-01-25 12:43:54 +0100150/**
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:
Jens Axboe320ae512013-10-24 09:20:05 +0100160 * spin_lock_irq(q->queue_lock or q->mq_flush_lock)
Tejun Heoae1b1532011-01-25 12:43:54 +0100161 *
162 * RETURNS:
163 * %true if requests were added to the dispatch queue, %false otherwise.
164 */
165static bool blk_flush_complete_seq(struct request *rq, unsigned int seq,
166 int error)
Jens Axboe86db1e22008-01-29 14:53:40 +0100167{
Tejun Heoae1b1532011-01-25 12:43:54 +0100168 struct request_queue *q = rq->q;
169 struct list_head *pending = &q->flush_queue[q->flush_pending_idx];
Jens Axboe320ae512013-10-24 09:20:05 +0100170 bool queued = false, kicked;
Jens Axboe86db1e22008-01-29 14:53:40 +0100171
Tejun Heoae1b1532011-01-25 12:43:54 +0100172 BUG_ON(rq->flush.seq & seq);
173 rq->flush.seq |= seq;
Jens Axboe86db1e22008-01-29 14:53:40 +0100174
Tejun Heoae1b1532011-01-25 12:43:54 +0100175 if (likely(!error))
176 seq = blk_flush_cur_seq(rq);
177 else
178 seq = REQ_FSEQ_DONE;
Tejun Heo28e7d182010-09-03 11:56:16 +0200179
Tejun Heoae1b1532011-01-25 12:43:54 +0100180 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);
Tejun Heo28e7d182010-09-03 11:56:16 +0200187 break;
Tejun Heoae1b1532011-01-25 12:43:54 +0100188
189 case REQ_FSEQ_DATA:
190 list_move_tail(&rq->flush.list, &q->flush_data_in_flight);
Mike Snitzer10beafc2014-03-08 20:19:20 -0700191 queued = blk_flush_queue_rq(rq, true);
Tejun Heoae1b1532011-01-25 12:43:54 +0100192 break;
193
194 case REQ_FSEQ_DONE:
Tejun Heo09d60c72010-09-03 11:56:17 +0200195 /*
Tejun Heoae1b1532011-01-25 12:43:54 +0100196 * @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.
Tejun Heo09d60c72010-09-03 11:56:17 +0200200 */
Tejun Heoae1b1532011-01-25 12:43:54 +0100201 BUG_ON(!list_empty(&rq->queuelist));
202 list_del_init(&rq->flush.list);
203 blk_flush_restore_request(rq);
Jens Axboe320ae512013-10-24 09:20:05 +0100204 if (q->mq_ops)
205 blk_mq_end_io(rq, error);
206 else
207 __blk_end_request_all(rq, error);
Tejun Heo28e7d182010-09-03 11:56:16 +0200208 break;
Tejun Heoae1b1532011-01-25 12:43:54 +0100209
Tejun Heo28e7d182010-09-03 11:56:16 +0200210 default:
211 BUG();
212 }
Christoph Hellwigcde4c402010-09-03 11:56:17 +0200213
Jens Axboe320ae512013-10-24 09:20:05 +0100214 kicked = blk_kick_flush(q);
Jens Axboe320ae512013-10-24 09:20:05 +0100215 return kicked | queued;
Tejun Heo28e7d182010-09-03 11:56:16 +0200216}
217
Tejun Heoae1b1532011-01-25 12:43:54 +0100218static void flush_end_io(struct request *flush_rq, int error)
Jens Axboe86db1e22008-01-29 14:53:40 +0100219{
Tejun Heoae1b1532011-01-25 12:43:54 +0100220 struct request_queue *q = flush_rq->q;
Jens Axboe320ae512013-10-24 09:20:05 +0100221 struct list_head *running;
Tejun Heoae1b1532011-01-25 12:43:54 +0100222 bool queued = false;
223 struct request *rq, *n;
Jens Axboe320ae512013-10-24 09:20:05 +0100224 unsigned long flags = 0;
Tejun Heo8f11b3e2008-11-28 13:32:05 +0900225
Shaohua Li22302372014-05-30 08:06:42 -0600226 if (q->mq_ops) {
Jens Axboe320ae512013-10-24 09:20:05 +0100227 spin_lock_irqsave(&q->mq_flush_lock, flags);
Ming Lei14b83e12014-06-05 00:23:55 +0800228 q->flush_rq->tag = -1;
Shaohua Li22302372014-05-30 08:06:42 -0600229 }
Christoph Hellwig18741982014-02-10 09:29:00 -0700230
Jens Axboe320ae512013-10-24 09:20:05 +0100231 running = &q->flush_queue[q->flush_running_idx];
Tejun Heoae1b1532011-01-25 12:43:54 +0100232 BUG_ON(q->flush_pending_idx == q->flush_running_idx);
233
234 /* account completion of the flush request */
235 q->flush_running_idx ^= 1;
Jens Axboe320ae512013-10-24 09:20:05 +0100236
237 if (!q->mq_ops)
238 elv_completed_request(q, flush_rq);
Tejun Heoae1b1532011-01-25 12:43:54 +0100239
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);
Tejun Heo28e7d182010-09-03 11:56:16 +0200246 }
247
Jens Axboe86db1e22008-01-29 14:53:40 +0100248 /*
shaohua.li@intel.com3ac0cc42011-05-06 11:34:41 -0600249 * 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.
Jens Axboe86db1e22008-01-29 14:53:40 +0100258 */
Jens Axboe320ae512013-10-24 09:20:05 +0100259 if (queued || q->flush_queue_delayed) {
Christoph Hellwig18741982014-02-10 09:29:00 -0700260 WARN_ON(q->mq_ops);
261 blk_run_queue_async(q);
Jens Axboe320ae512013-10-24 09:20:05 +0100262 }
shaohua.li@intel.com3ac0cc42011-05-06 11:34:41 -0600263 q->flush_queue_delayed = 0;
Jens Axboe320ae512013-10-24 09:20:05 +0100264 if (q->mq_ops)
265 spin_unlock_irqrestore(&q->mq_flush_lock, flags);
266}
267
Tejun Heoae1b1532011-01-25 12:43:54 +0100268/**
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:
Jens Axboe320ae512013-10-24 09:20:05 +0100276 * spin_lock_irq(q->queue_lock or q->mq_flush_lock)
Tejun Heoae1b1532011-01-25 12:43:54 +0100277 *
278 * RETURNS:
279 * %true if flush was issued, %false otherwise.
280 */
281static bool blk_kick_flush(struct request_queue *q)
282{
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;
Tejun Heo28e7d182010-09-03 11:56:16 +0200296
297 /*
Tejun Heoae1b1532011-01-25 12:43:54 +0100298 * Issue flush and toggle pending_idx. This makes pending_idx
299 * different from running_idx, which means flush is in flight.
Tejun Heo28e7d182010-09-03 11:56:16 +0200300 */
Jens Axboe320ae512013-10-24 09:20:05 +0100301 q->flush_pending_idx ^= 1;
Christoph Hellwig18741982014-02-10 09:29:00 -0700302
Christoph Hellwig9d74e252014-04-14 10:30:07 +0200303 blk_rq_init(q, q->flush_rq);
Christoph Hellwig8727af42014-04-14 10:30:08 +0200304 if (q->mq_ops)
305 blk_mq_clone_flush_request(q->flush_rq, first_rq);
Jens Axboe320ae512013-10-24 09:20:05 +0100306
Christoph Hellwig18741982014-02-10 09:29:00 -0700307 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;
Jens Axboe86db1e22008-01-29 14:53:40 +0100311
Mike Snitzer10beafc2014-03-08 20:19:20 -0700312 return blk_flush_queue_rq(q->flush_rq, false);
Tejun Heoae1b1532011-01-25 12:43:54 +0100313}
314
315static void flush_data_end_io(struct request *rq, int error)
316{
317 struct request_queue *q = rq->q;
Tejun Heoae1b1532011-01-25 12:43:54 +0100318
Jens Axboe86db1e22008-01-29 14:53:40 +0100319 /*
Tejun Heoe83a46b2011-03-04 19:09:02 +0100320 * After populating an empty queue, kick it to avoid stall. Read
321 * the comment in flush_end_io().
Jens Axboe86db1e22008-01-29 14:53:40 +0100322 */
Jens Axboe73c10102011-03-08 13:19:51 +0100323 if (blk_flush_complete_seq(rq, REQ_FSEQ_DATA, error))
Christoph Hellwig24ecfbe2011-04-18 11:41:33 +0200324 blk_run_queue_async(q);
Tejun Heoae1b1532011-01-25 12:43:54 +0100325}
326
Jens Axboe320ae512013-10-24 09:20:05 +0100327static 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
Tejun Heoae1b1532011-01-25 12:43:54 +0100347/**
348 * blk_insert_flush - insert a new FLUSH/FUA request
349 * @rq: request to insert
350 *
Jens Axboeb710a482011-03-30 09:52:30 +0200351 * To be called from __elv_add_request() for %ELEVATOR_INSERT_FLUSH insertions.
Jens Axboe320ae512013-10-24 09:20:05 +0100352 * or __blk_mq_run_hw_queue() to dispatch request.
Tejun Heoae1b1532011-01-25 12:43:54 +0100353 * @rq is being submitted. Analyze what needs to be done and put it on the
354 * right queue.
355 *
356 * CONTEXT:
Jens Axboe320ae512013-10-24 09:20:05 +0100357 * spin_lock_irq(q->queue_lock) in !mq case
Tejun Heoae1b1532011-01-25 12:43:54 +0100358 */
359void blk_insert_flush(struct request *rq)
360{
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);
364
Tejun Heoae1b1532011-01-25 12:43:54 +0100365 /*
366 * @policy now records what operations need to be done. Adjust
367 * REQ_FLUSH and FUA for the driver.
368 */
Christoph Hellwig18741982014-02-10 09:29:00 -0700369 rq->cmd_flags &= ~REQ_FLUSH;
Tejun Heoae1b1532011-01-25 12:43:54 +0100370 if (!(fflags & REQ_FUA))
Tejun Heo4fed9472010-09-03 11:56:17 +0200371 rq->cmd_flags &= ~REQ_FUA;
Jens Axboe86db1e22008-01-29 14:53:40 +0100372
Tejun Heoae1b1532011-01-25 12:43:54 +0100373 /*
Jeff Moyer4853aba2011-08-15 21:37:25 +0200374 * 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) {
Jens Axboe320ae512013-10-24 09:20:05 +0100380 if (q->mq_ops)
381 blk_mq_end_io(rq, 0);
382 else
383 __blk_end_bidi_request(rq, 0, 0, 0);
Jeff Moyer4853aba2011-08-15 21:37:25 +0200384 return;
385 }
386
Jeff Moyer834f9f62011-10-17 12:57:22 +0200387 BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */
Jeff Moyer4853aba2011-08-15 21:37:25 +0200388
389 /*
Tejun Heoae1b1532011-01-25 12:43:54 +0100390 * 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))) {
Jens Axboe320ae512013-10-24 09:20:05 +0100396 if (q->mq_ops) {
Christoph Hellwigfeb71da2014-02-20 15:32:37 -0800397 blk_mq_insert_request(rq, false, false, true);
Jens Axboe320ae512013-10-24 09:20:05 +0100398 } else
399 list_add_tail(&rq->queuelist, &q->queue_head);
Tejun Heoae1b1532011-01-25 12:43:54 +0100400 return;
401 }
402
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);
409 rq->cmd_flags |= REQ_FLUSH_SEQ;
Jeff Moyer4853aba2011-08-15 21:37:25 +0200410 rq->flush.saved_end_io = rq->end_io; /* Usually NULL */
Jens Axboe320ae512013-10-24 09:20:05 +0100411 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 }
Tejun Heoae1b1532011-01-25 12:43:54 +0100419 rq->end_io = flush_data_end_io;
420
421 blk_flush_complete_seq(rq, REQ_FSEQ_ACTIONS & ~policy, 0);
422}
423
424/**
Jens Axboe86db1e22008-01-29 14:53:40 +0100425 * blkdev_issue_flush - queue a flush
426 * @bdev: blockdev to issue flush for
Dmitry Monakhovfbd9b092010-04-28 17:55:06 +0400427 * @gfp_mask: memory allocation flags (for bio_alloc)
Jens Axboe86db1e22008-01-29 14:53:40 +0100428 * @error_sector: error sector
429 *
430 * Description:
431 * Issue a flush for the block device in question. Caller can supply
432 * room for storing the error offset in case of a flush error, if they
Dmitry Monakhovf17e2322010-04-28 17:55:07 +0400433 * wish to. If WAIT flag is not passed then caller may check only what
434 * request was pushed in some internal queue for later handling.
Jens Axboe86db1e22008-01-29 14:53:40 +0100435 */
Dmitry Monakhovfbd9b092010-04-28 17:55:06 +0400436int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200437 sector_t *error_sector)
Jens Axboe86db1e22008-01-29 14:53:40 +0100438{
Jens Axboe86db1e22008-01-29 14:53:40 +0100439 struct request_queue *q;
440 struct bio *bio;
Dmitry Monakhovfbd9b092010-04-28 17:55:06 +0400441 int ret = 0;
Jens Axboe86db1e22008-01-29 14:53:40 +0100442
443 if (bdev->bd_disk == NULL)
444 return -ENXIO;
445
446 q = bdev_get_queue(bdev);
447 if (!q)
448 return -ENXIO;
449
Dave Chinnerf10d9f62010-07-13 17:50:50 +1000450 /*
451 * some block devices may not have their queue correctly set up here
452 * (e.g. loop device without a backing file) and so issuing a flush
453 * here will panic. Ensure there is a request function before issuing
Tejun Heod391a2d2010-09-03 11:56:17 +0200454 * the flush.
Dave Chinnerf10d9f62010-07-13 17:50:50 +1000455 */
456 if (!q->make_request_fn)
457 return -ENXIO;
458
Dmitry Monakhovfbd9b092010-04-28 17:55:06 +0400459 bio = bio_alloc(gfp_mask, 0);
Jens Axboe86db1e22008-01-29 14:53:40 +0100460 bio->bi_bdev = bdev;
Dmitry Monakhovf17e2322010-04-28 17:55:07 +0400461
Kent Overstreet33879d42013-11-23 22:33:32 -0800462 ret = submit_bio_wait(WRITE_FLUSH, bio);
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200463
464 /*
465 * The driver must store the error location in ->bi_sector, if
466 * it supports it. For non-stacked drivers, this should be
467 * copied from blk_rq_pos(rq).
468 */
469 if (error_sector)
Kent Overstreet4f024f32013-10-11 15:44:27 -0700470 *error_sector = bio->bi_iter.bi_sector;
Jens Axboe86db1e22008-01-29 14:53:40 +0100471
Jens Axboe86db1e22008-01-29 14:53:40 +0100472 bio_put(bio);
473 return ret;
474}
Jens Axboe86db1e22008-01-29 14:53:40 +0100475EXPORT_SYMBOL(blkdev_issue_flush);
Jens Axboe320ae512013-10-24 09:20:05 +0100476
477void blk_mq_init_flush(struct request_queue *q)
478{
479 spin_lock_init(&q->mq_flush_lock);
Jens Axboe320ae512013-10-24 09:20:05 +0100480}