Branch data     Line data    Source code

       1                 :            : // SPDX-License-Identifier: GPL-2.0
       2                 :            : /*
       3                 :            :  * Functions to sequence PREFLUSH and FUA writes.
       4                 :            :  *
       5                 :            :  * Copyright (C) 2011           Max Planck Institute for Gravitational Physics
       6                 :            :  * Copyright (C) 2011           Tejun Heo <tj@kernel.org>
       7                 :            :  *
       8                 :            :  * REQ_{PREFLUSH|FUA} requests are decomposed to sequences consisted of three
       9                 :            :  * optional steps - PREFLUSH, DATA and POSTFLUSH - according to the request
      10                 :            :  * properties and hardware capability.
      11                 :            :  *
      12                 :            :  * If a request doesn't have data, only REQ_PREFLUSH makes sense, which
      13                 :            :  * indicates a simple flush request.  If there is data, REQ_PREFLUSH indicates
      14                 :            :  * that the device cache should be flushed before the data is executed, and
      15                 :            :  * REQ_FUA means that the data must be on non-volatile media on request
      16                 :            :  * completion.
      17                 :            :  *
      18                 :            :  * If the device doesn't have writeback cache, PREFLUSH and FUA don't make any
      19                 :            :  * difference.  The requests are either completed immediately if there's no data
      20                 :            :  * or executed as normal requests otherwise.
      21                 :            :  *
      22                 :            :  * If the device has writeback cache and supports FUA, REQ_PREFLUSH is
      23                 :            :  * translated to PREFLUSH but REQ_FUA is passed down directly with DATA.
      24                 :            :  *
      25                 :            :  * If the device has writeback cache and doesn't support FUA, REQ_PREFLUSH
      26                 :            :  * is translated to PREFLUSH and REQ_FUA to POSTFLUSH.
      27                 :            :  *
      28                 :            :  * The actual execution of flush is double buffered.  Whenever a request
      29                 :            :  * needs to execute PRE or POSTFLUSH, it queues at
      30                 :            :  * fq->flush_queue[fq->flush_pending_idx].  Once certain criteria are met, a
      31                 :            :  * REQ_OP_FLUSH is issued and the pending_idx is toggled.  When the flush
      32                 :            :  * completes, all the requests which were pending are proceeded to the next
      33                 :            :  * step.  This allows arbitrary merging of different types of PREFLUSH/FUA
      34                 :            :  * requests.
      35                 :            :  *
      36                 :            :  * Currently, the following conditions are used to determine when to issue
      37                 :            :  * flush.
      38                 :            :  *
      39                 :            :  * C1. At any given time, only one flush shall be in progress.  This makes
      40                 :            :  *     double buffering sufficient.
      41                 :            :  *
      42                 :            :  * C2. Flush is deferred if any request is executing DATA of its sequence.
      43                 :            :  *     This avoids issuing separate POSTFLUSHes for requests which shared
      44                 :            :  *     PREFLUSH.
      45                 :            :  *
      46                 :            :  * C3. The second condition is ignored if there is a request which has
      47                 :            :  *     waited longer than FLUSH_PENDING_TIMEOUT.  This is to avoid
      48                 :            :  *     starvation in the unlikely case where there are continuous stream of
      49                 :            :  *     FUA (without PREFLUSH) requests.
      50                 :            :  *
      51                 :            :  * For devices which support FUA, it isn't clear whether C2 (and thus C3)
      52                 :            :  * is beneficial.
      53                 :            :  *
      54                 :            :  * Note that a sequenced PREFLUSH/FUA request with DATA is completed twice.
      55                 :            :  * Once while executing DATA and again after the whole sequence is
      56                 :            :  * complete.  The first completion updates the contained bio but doesn't
      57                 :            :  * finish it so that the bio submitter is notified only after the whole
      58                 :            :  * sequence is complete.  This is implemented by testing RQF_FLUSH_SEQ in
      59                 :            :  * req_bio_endio().
      60                 :            :  *
      61                 :            :  * The above peculiarity requires that each PREFLUSH/FUA request has only one
      62                 :            :  * bio attached to it, which is guaranteed as they aren't allowed to be
      63                 :            :  * merged in the usual way.
      64                 :            :  */
      65                 :            : 
      66                 :            : #include <linux/kernel.h>
      67                 :            : #include <linux/module.h>
      68                 :            : #include <linux/bio.h>
      69                 :            : #include <linux/blkdev.h>
      70                 :            : #include <linux/gfp.h>
      71                 :            : #include <linux/blk-mq.h>
      72                 :            : #include <linux/lockdep.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                 :            : /* PREFLUSH/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 void blk_kick_flush(struct request_queue *q,
      97                 :            :                            struct blk_flush_queue *fq, unsigned int flags);
      98                 :            : 
      99                 :          0 : static unsigned int blk_flush_policy(unsigned long fflags, struct request *rq)
     100                 :            : {
     101                 :            :         unsigned int policy = 0;
     102                 :            : 
     103                 :          0 :         if (blk_rq_sectors(rq))
     104                 :            :                 policy |= REQ_FSEQ_DATA;
     105                 :            : 
     106                 :          0 :         if (fflags & (1UL << QUEUE_FLAG_WC)) {
     107                 :          0 :                 if (rq->cmd_flags & REQ_PREFLUSH)
     108                 :          0 :                         policy |= REQ_FSEQ_PREFLUSH;
     109                 :          0 :                 if (!(fflags & (1UL << QUEUE_FLAG_FUA)) &&
     110                 :          0 :                     (rq->cmd_flags & REQ_FUA))
     111                 :          0 :                         policy |= REQ_FSEQ_POSTFLUSH;
     112                 :            :         }
     113                 :          0 :         return policy;
     114                 :            : }
     115                 :            : 
     116                 :            : static unsigned int blk_flush_cur_seq(struct request *rq)
     117                 :            : {
     118                 :          0 :         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                 :          0 :         rq->bio = rq->biotail;
     129                 :            : 
     130                 :            :         /* make @rq a normal request */
     131                 :          0 :         rq->rq_flags &= ~RQF_FLUSH_SEQ;
     132                 :          0 :         rq->end_io = rq->flush.saved_end_io;
     133                 :            : }
     134                 :            : 
     135                 :            : static void blk_flush_queue_rq(struct request *rq, bool add_front)
     136                 :            : {
     137                 :          0 :         blk_mq_add_to_requeue_list(rq, add_front, true);
     138                 :            : }
     139                 :            : 
     140                 :            : /**
     141                 :            :  * blk_flush_complete_seq - complete flush sequence
     142                 :            :  * @rq: PREFLUSH/FUA request being sequenced
     143                 :            :  * @fq: flush queue
     144                 :            :  * @seq: sequences to complete (mask of %REQ_FSEQ_*, can be zero)
     145                 :            :  * @error: whether an error occurred
     146                 :            :  *
     147                 :            :  * @rq just completed @seq part of its flush sequence, record the
     148                 :            :  * completion and trigger the next step.
     149                 :            :  *
     150                 :            :  * CONTEXT:
     151                 :            :  * spin_lock_irq(fq->mq_flush_lock)
     152                 :            :  *
     153                 :            :  * RETURNS:
     154                 :            :  * %true if requests were added to the dispatch queue, %false otherwise.
     155                 :            :  */
     156                 :          0 : static void blk_flush_complete_seq(struct request *rq,
     157                 :            :                                    struct blk_flush_queue *fq,
     158                 :            :                                    unsigned int seq, blk_status_t error)
     159                 :            : {
     160                 :          0 :         struct request_queue *q = rq->q;
     161                 :          0 :         struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx];
     162                 :            :         unsigned int cmd_flags;
     163                 :            : 
     164                 :          0 :         BUG_ON(rq->flush.seq & seq);
     165                 :          0 :         rq->flush.seq |= seq;
     166                 :          0 :         cmd_flags = rq->cmd_flags;
     167                 :            : 
     168                 :          0 :         if (likely(!error))
     169                 :            :                 seq = blk_flush_cur_seq(rq);
     170                 :            :         else
     171                 :            :                 seq = REQ_FSEQ_DONE;
     172                 :            : 
     173                 :          0 :         switch (seq) {
     174                 :            :         case REQ_FSEQ_PREFLUSH:
     175                 :            :         case REQ_FSEQ_POSTFLUSH:
     176                 :            :                 /* queue for flush */
     177                 :          0 :                 if (list_empty(pending))
     178                 :          0 :                         fq->flush_pending_since = jiffies;
     179                 :          0 :                 list_move_tail(&rq->flush.list, pending);
     180                 :            :                 break;
     181                 :            : 
     182                 :            :         case REQ_FSEQ_DATA:
     183                 :          0 :                 list_move_tail(&rq->flush.list, &fq->flush_data_in_flight);
     184                 :            :                 blk_flush_queue_rq(rq, true);
     185                 :            :                 break;
     186                 :            : 
     187                 :            :         case REQ_FSEQ_DONE:
     188                 :            :                 /*
     189                 :            :                  * @rq was previously adjusted by blk_flush_issue() for
     190                 :            :                  * flush sequencing and may already have gone through the
     191                 :            :                  * flush data request completion path.  Restore @rq for
     192                 :            :                  * normal completion and end it.
     193                 :            :                  */
     194                 :          0 :                 BUG_ON(!list_empty(&rq->queuelist));
     195                 :          0 :                 list_del_init(&rq->flush.list);
     196                 :            :                 blk_flush_restore_request(rq);
     197                 :          0 :                 blk_mq_end_request(rq, error);
     198                 :          0 :                 break;
     199                 :            : 
     200                 :            :         default:
     201                 :          0 :                 BUG();
     202                 :            :         }
     203                 :            : 
     204                 :          0 :         blk_kick_flush(q, fq, cmd_flags);
     205                 :          0 : }
     206                 :            : 
     207                 :          0 : static void flush_end_io(struct request *flush_rq, blk_status_t error)
     208                 :            : {
     209                 :          0 :         struct request_queue *q = flush_rq->q;
     210                 :            :         struct list_head *running;
     211                 :            :         struct request *rq, *n;
     212                 :            :         unsigned long flags = 0;
     213                 :          0 :         struct blk_flush_queue *fq = blk_get_flush_queue(q, flush_rq->mq_ctx);
     214                 :            :         struct blk_mq_hw_ctx *hctx;
     215                 :            : 
     216                 :            :         /* release the tag's ownership to the req cloned from */
     217                 :          0 :         spin_lock_irqsave(&fq->mq_flush_lock, flags);
     218                 :            : 
     219                 :          0 :         if (!refcount_dec_and_test(&flush_rq->ref)) {
     220                 :          0 :                 fq->rq_status = error;
     221                 :            :                 spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
     222                 :          0 :                 return;
     223                 :            :         }
     224                 :            : 
     225                 :          0 :         if (fq->rq_status != BLK_STS_OK)
     226                 :            :                 error = fq->rq_status;
     227                 :            : 
     228                 :          0 :         hctx = flush_rq->mq_hctx;
     229                 :          0 :         if (!q->elevator) {
     230                 :          0 :                 blk_mq_tag_set_rq(hctx, flush_rq->tag, fq->orig_rq);
     231                 :          0 :                 flush_rq->tag = -1;
     232                 :            :         } else {
     233                 :          0 :                 blk_mq_put_driver_tag(flush_rq);
     234                 :          0 :                 flush_rq->internal_tag = -1;
     235                 :            :         }
     236                 :            : 
     237                 :          0 :         running = &fq->flush_queue[fq->flush_running_idx];
     238                 :          0 :         BUG_ON(fq->flush_pending_idx == fq->flush_running_idx);
     239                 :            : 
     240                 :            :         /* account completion of the flush request */
     241                 :          0 :         fq->flush_running_idx ^= 1;
     242                 :            : 
     243                 :            :         /* and push the waiting requests to the next stage */
     244                 :          0 :         list_for_each_entry_safe(rq, n, running, flush.list) {
     245                 :            :                 unsigned int seq = blk_flush_cur_seq(rq);
     246                 :            : 
     247                 :          0 :                 BUG_ON(seq != REQ_FSEQ_PREFLUSH && seq != REQ_FSEQ_POSTFLUSH);
     248                 :          0 :                 blk_flush_complete_seq(rq, fq, seq, error);
     249                 :            :         }
     250                 :            : 
     251                 :          0 :         fq->flush_queue_delayed = 0;
     252                 :            :         spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
     253                 :            : }
     254                 :            : 
     255                 :            : /**
     256                 :            :  * blk_kick_flush - consider issuing flush request
     257                 :            :  * @q: request_queue being kicked
     258                 :            :  * @fq: flush queue
     259                 :            :  * @flags: cmd_flags of the original request
     260                 :            :  *
     261                 :            :  * Flush related states of @q have changed, consider issuing flush request.
     262                 :            :  * Please read the comment at the top of this file for more info.
     263                 :            :  *
     264                 :            :  * CONTEXT:
     265                 :            :  * spin_lock_irq(fq->mq_flush_lock)
     266                 :            :  *
     267                 :            :  */
     268                 :          0 : static void blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
     269                 :            :                            unsigned int flags)
     270                 :            : {
     271                 :          0 :         struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx];
     272                 :            :         struct request *first_rq =
     273                 :          0 :                 list_first_entry(pending, struct request, flush.list);
     274                 :          0 :         struct request *flush_rq = fq->flush_rq;
     275                 :            : 
     276                 :            :         /* C1 described at the top of this file */
     277                 :          0 :         if (fq->flush_pending_idx != fq->flush_running_idx || list_empty(pending))
     278                 :            :                 return;
     279                 :            : 
     280                 :            :         /* C2 and C3
     281                 :            :          *
     282                 :            :          * For blk-mq + scheduling, we can risk having all driver tags
     283                 :            :          * assigned to empty flushes, and we deadlock if we are expecting
     284                 :            :          * other requests to make progress. Don't defer for that case.
     285                 :            :          */
     286                 :          0 :         if (!list_empty(&fq->flush_data_in_flight) && q->elevator &&
     287                 :          0 :             time_before(jiffies,
     288                 :            :                         fq->flush_pending_since + FLUSH_PENDING_TIMEOUT))
     289                 :            :                 return;
     290                 :            : 
     291                 :            :         /*
     292                 :            :          * Issue flush and toggle pending_idx.  This makes pending_idx
     293                 :            :          * different from running_idx, which means flush is in flight.
     294                 :            :          */
     295                 :          0 :         fq->flush_pending_idx ^= 1;
     296                 :            : 
     297                 :          0 :         blk_rq_init(q, flush_rq);
     298                 :            : 
     299                 :            :         /*
     300                 :            :          * In case of none scheduler, borrow tag from the first request
     301                 :            :          * since they can't be in flight at the same time. And acquire
     302                 :            :          * the tag's ownership for flush req.
     303                 :            :          *
     304                 :            :          * In case of IO scheduler, flush rq need to borrow scheduler tag
     305                 :            :          * just for cheating put/get driver tag.
     306                 :            :          */
     307                 :          0 :         flush_rq->mq_ctx = first_rq->mq_ctx;
     308                 :          0 :         flush_rq->mq_hctx = first_rq->mq_hctx;
     309                 :            : 
     310                 :          0 :         if (!q->elevator) {
     311                 :          0 :                 fq->orig_rq = first_rq;
     312                 :          0 :                 flush_rq->tag = first_rq->tag;
     313                 :          0 :                 blk_mq_tag_set_rq(flush_rq->mq_hctx, first_rq->tag, flush_rq);
     314                 :            :         } else {
     315                 :          0 :                 flush_rq->internal_tag = first_rq->internal_tag;
     316                 :            :         }
     317                 :            : 
     318                 :          0 :         flush_rq->cmd_flags = REQ_OP_FLUSH | REQ_PREFLUSH;
     319                 :          0 :         flush_rq->cmd_flags |= (flags & REQ_DRV) | (flags & REQ_FAILFAST_MASK);
     320                 :          0 :         flush_rq->rq_flags |= RQF_FLUSH_SEQ;
     321                 :          0 :         flush_rq->rq_disk = first_rq->rq_disk;
     322                 :          0 :         flush_rq->end_io = flush_end_io;
     323                 :            : 
     324                 :            :         blk_flush_queue_rq(flush_rq, false);
     325                 :            : }
     326                 :            : 
     327                 :          0 : static void mq_flush_data_end_io(struct request *rq, blk_status_t error)
     328                 :            : {
     329                 :          0 :         struct request_queue *q = rq->q;
     330                 :          0 :         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
     331                 :          0 :         struct blk_mq_ctx *ctx = rq->mq_ctx;
     332                 :            :         unsigned long flags;
     333                 :            :         struct blk_flush_queue *fq = blk_get_flush_queue(q, ctx);
     334                 :            : 
     335                 :          0 :         if (q->elevator) {
     336                 :          0 :                 WARN_ON(rq->tag < 0);
     337                 :          0 :                 blk_mq_put_driver_tag(rq);
     338                 :            :         }
     339                 :            : 
     340                 :            :         /*
     341                 :            :          * After populating an empty queue, kick it to avoid stall.  Read
     342                 :            :          * the comment in flush_end_io().
     343                 :            :          */
     344                 :          0 :         spin_lock_irqsave(&fq->mq_flush_lock, flags);
     345                 :          0 :         blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error);
     346                 :            :         spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
     347                 :            : 
     348                 :          0 :         blk_mq_sched_restart(hctx);
     349                 :          0 : }
     350                 :            : 
     351                 :            : /**
     352                 :            :  * blk_insert_flush - insert a new PREFLUSH/FUA request
     353                 :            :  * @rq: request to insert
     354                 :            :  *
     355                 :            :  * To be called from __elv_add_request() for %ELEVATOR_INSERT_FLUSH insertions.
     356                 :            :  * or __blk_mq_run_hw_queue() to dispatch request.
     357                 :            :  * @rq is being submitted.  Analyze what needs to be done and put it on the
     358                 :            :  * right queue.
     359                 :            :  */
     360                 :          0 : void blk_insert_flush(struct request *rq)
     361                 :            : {
     362                 :          0 :         struct request_queue *q = rq->q;
     363                 :          0 :         unsigned long fflags = q->queue_flags;       /* may change, cache */
     364                 :          0 :         unsigned int policy = blk_flush_policy(fflags, rq);
     365                 :          0 :         struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx);
     366                 :            : 
     367                 :            :         /*
     368                 :            :          * @policy now records what operations need to be done.  Adjust
     369                 :            :          * REQ_PREFLUSH and FUA for the driver.
     370                 :            :          */
     371                 :          0 :         rq->cmd_flags &= ~REQ_PREFLUSH;
     372                 :          0 :         if (!(fflags & (1UL << QUEUE_FLAG_FUA)))
     373                 :          0 :                 rq->cmd_flags &= ~REQ_FUA;
     374                 :            : 
     375                 :            :         /*
     376                 :            :          * REQ_PREFLUSH|REQ_FUA implies REQ_SYNC, so if we clear any
     377                 :            :          * of those flags, we have to set REQ_SYNC to avoid skewing
     378                 :            :          * the request accounting.
     379                 :            :          */
     380                 :          0 :         rq->cmd_flags |= REQ_SYNC;
     381                 :            : 
     382                 :            :         /*
     383                 :            :          * An empty flush handed down from a stacking driver may
     384                 :            :          * translate into nothing if the underlying device does not
     385                 :            :          * advertise a write-back cache.  In this case, simply
     386                 :            :          * complete the request.
     387                 :            :          */
     388                 :          0 :         if (!policy) {
     389                 :          0 :                 blk_mq_end_request(rq, 0);
     390                 :          0 :                 return;
     391                 :            :         }
     392                 :            : 
     393                 :          0 :         BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */
     394                 :            : 
     395                 :            :         /*
     396                 :            :          * If there's data but flush is not necessary, the request can be
     397                 :            :          * processed directly without going through flush machinery.  Queue
     398                 :            :          * for normal execution.
     399                 :            :          */
     400                 :          0 :         if ((policy & REQ_FSEQ_DATA) &&
     401                 :            :             !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
     402                 :          0 :                 blk_mq_request_bypass_insert(rq, false, false);
     403                 :          0 :                 return;
     404                 :            :         }
     405                 :            : 
     406                 :            :         /*
     407                 :            :          * @rq should go through flush machinery.  Mark it part of flush
     408                 :            :          * sequence and submit for further processing.
     409                 :            :          */
     410                 :          0 :         memset(&rq->flush, 0, sizeof(rq->flush));
     411                 :          0 :         INIT_LIST_HEAD(&rq->flush.list);
     412                 :          0 :         rq->rq_flags |= RQF_FLUSH_SEQ;
     413                 :          0 :         rq->flush.saved_end_io = rq->end_io; /* Usually NULL */
     414                 :            : 
     415                 :          0 :         rq->end_io = mq_flush_data_end_io;
     416                 :            : 
     417                 :            :         spin_lock_irq(&fq->mq_flush_lock);
     418                 :          0 :         blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0);
     419                 :            :         spin_unlock_irq(&fq->mq_flush_lock);
     420                 :            : }
     421                 :            : 
     422                 :            : /**
     423                 :            :  * blkdev_issue_flush - queue a flush
     424                 :            :  * @bdev:       blockdev to issue flush for
     425                 :            :  * @gfp_mask:   memory allocation flags (for bio_alloc)
     426                 :            :  * @error_sector:       error sector
     427                 :            :  *
     428                 :            :  * Description:
     429                 :            :  *    Issue a flush for the block device in question. Caller can supply
     430                 :            :  *    room for storing the error offset in case of a flush error, if they
     431                 :            :  *    wish to.
     432                 :            :  */
     433                 :          3 : int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
     434                 :            :                 sector_t *error_sector)
     435                 :            : {
     436                 :            :         struct request_queue *q;
     437                 :            :         struct bio *bio;
     438                 :            :         int ret = 0;
     439                 :            : 
     440                 :          3 :         if (bdev->bd_disk == NULL)
     441                 :            :                 return -ENXIO;
     442                 :            : 
     443                 :            :         q = bdev_get_queue(bdev);
     444                 :          3 :         if (!q)
     445                 :            :                 return -ENXIO;
     446                 :            : 
     447                 :            :         /*
     448                 :            :          * some block devices may not have their queue correctly set up here
     449                 :            :          * (e.g. loop device without a backing file) and so issuing a flush
     450                 :            :          * here will panic. Ensure there is a request function before issuing
     451                 :            :          * the flush.
     452                 :            :          */
     453                 :          3 :         if (!q->make_request_fn)
     454                 :            :                 return -ENXIO;
     455                 :            : 
     456                 :            :         bio = bio_alloc(gfp_mask, 0);
     457                 :          3 :         bio_set_dev(bio, bdev);
     458                 :          3 :         bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
     459                 :            : 
     460                 :          3 :         ret = submit_bio_wait(bio);
     461                 :            : 
     462                 :            :         /*
     463                 :            :          * The driver must store the error location in ->bi_sector, if
     464                 :            :          * it supports it. For non-stacked drivers, this should be
     465                 :            :          * copied from blk_rq_pos(rq).
     466                 :            :          */
     467                 :          3 :         if (error_sector)
     468                 :          0 :                 *error_sector = bio->bi_iter.bi_sector;
     469                 :            : 
     470                 :          3 :         bio_put(bio);
     471                 :          3 :         return ret;
     472                 :            : }
     473                 :            : EXPORT_SYMBOL(blkdev_issue_flush);
     474                 :            : 
     475                 :          3 : struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q,
     476                 :            :                 int node, int cmd_size, gfp_t flags)
     477                 :            : {
     478                 :            :         struct blk_flush_queue *fq;
     479                 :            :         int rq_sz = sizeof(struct request);
     480                 :            : 
     481                 :          3 :         fq = kzalloc_node(sizeof(*fq), flags, node);
     482                 :          3 :         if (!fq)
     483                 :            :                 goto fail;
     484                 :            : 
     485                 :          3 :         spin_lock_init(&fq->mq_flush_lock);
     486                 :            : 
     487                 :          3 :         rq_sz = round_up(rq_sz + cmd_size, cache_line_size());
     488                 :          3 :         fq->flush_rq = kzalloc_node(rq_sz, flags, node);
     489                 :          3 :         if (!fq->flush_rq)
     490                 :            :                 goto fail_rq;
     491                 :            : 
     492                 :          3 :         INIT_LIST_HEAD(&fq->flush_queue[0]);
     493                 :          3 :         INIT_LIST_HEAD(&fq->flush_queue[1]);
     494                 :          3 :         INIT_LIST_HEAD(&fq->flush_data_in_flight);
     495                 :            : 
     496                 :            :         lockdep_register_key(&fq->key);
     497                 :            :         lockdep_set_class(&fq->mq_flush_lock, &fq->key);
     498                 :            : 
     499                 :          3 :         return fq;
     500                 :            : 
     501                 :            :  fail_rq:
     502                 :          0 :         kfree(fq);
     503                 :            :  fail:
     504                 :            :         return NULL;
     505                 :            : }
     506                 :            : 
     507                 :          0 : void blk_free_flush_queue(struct blk_flush_queue *fq)
     508                 :            : {
     509                 :            :         /* bio based request queue hasn't flush queue */
     510                 :          0 :         if (!fq)
     511                 :          0 :                 return;
     512                 :            : 
     513                 :            :         lockdep_unregister_key(&fq->key);
     514                 :          0 :         kfree(fq->flush_rq);
     515                 :          0 :         kfree(fq);
     516                 :            : }