block/blk-barrier.c

   1 /*
   2  * Functions related to barrier IO handling
   3  */
   4 #include <linux/kernel.h>
   5 #include <linux/module.h>
   6 #include <linux/bio.h>
   7 #include <linux/blkdev.h>
   8
   9 #include "blk.h"
  10
  11 /**
  12  * blk_queue_ordered - does this queue support ordered writes
  13  * @q:        the request queue
  14  * @ordered:  one of QUEUE_ORDERED_*
  15  * @prepare_flush_fn: rq setup helper for cache flush ordered writes
  16  *
  17  * Description:
  18  *   For journalled file systems, doing ordered writes on a commit
  19  *   block instead of explicitly doing wait_on_buffer (which is bad
  20  *   for performance) can be a big win. Block drivers supporting this
  21  *   feature should call this function and indicate so.
  22  *
  23  **/
  24 int blk_queue_ordered(struct request_queue *q, unsigned ordered,
  25                       prepare_flush_fn *prepare_flush_fn)
  26 {
  27         if (!prepare_flush_fn && (ordered & (QUEUE_ORDERED_DO_PREFLUSH |
  28                                              QUEUE_ORDERED_DO_POSTFLUSH))) {
  29                 printk(KERN_ERR "%s: prepare_flush_fn required\n", __func__);
  30                 return -EINVAL;
  31         }
  32
  33         if (ordered != QUEUE_ORDERED_NONE &&
  34             ordered != QUEUE_ORDERED_DRAIN &&
  35             ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
  36             ordered != QUEUE_ORDERED_DRAIN_FUA &&
  37             ordered != QUEUE_ORDERED_TAG &&
  38             ordered != QUEUE_ORDERED_TAG_FLUSH &&
  39             ordered != QUEUE_ORDERED_TAG_FUA) {
  40                 printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
  41                 return -EINVAL;
  42         }
  43
  44         q->ordered = ordered;
  45         q->next_ordered = ordered;
  46         q->prepare_flush_fn = prepare_flush_fn;
  47
  48         return 0;
  49 }
  50 EXPORT_SYMBOL(blk_queue_ordered);
  51
  52 /*
  53  * Cache flushing for ordered writes handling
  54  */
  55 unsigned blk_ordered_cur_seq(struct request_queue *q)
  56 {
  57         if (!q->ordseq)
  58                 return 0;
  59         return 1 << ffz(q->ordseq);
  60 }
  61
  62 unsigned blk_ordered_req_seq(struct request *rq)
  63 {
  64         struct request_queue *q = rq->q;
  65
  66         BUG_ON(q->ordseq == 0);
  67
  68         if (rq == &q->pre_flush_rq)
  69                 return QUEUE_ORDSEQ_PREFLUSH;
  70         if (rq == &q->bar_rq)
  71                 return QUEUE_ORDSEQ_BAR;
  72         if (rq == &q->post_flush_rq)
  73                 return QUEUE_ORDSEQ_POSTFLUSH;
  74
  75         /*
  76          * !fs requests don't need to follow barrier ordering.  Always
  77          * put them at the front.  This fixes the following deadlock.
  78          *
  79          * http://thread.gmane.org/gmane.linux.kernel/537473
  80          */
  81         if (!blk_fs_request(rq))
  82                 return QUEUE_ORDSEQ_DRAIN;
  83
  84         if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
  85             (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
  86                 return QUEUE_ORDSEQ_DRAIN;
  87         else
  88                 return QUEUE_ORDSEQ_DONE;
  89 }
  90
  91 void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
  92 {
  93         struct request *rq;
  94
  95         if (error && !q->orderr)
  96                 q->orderr = error;
  97
  98         BUG_ON(q->ordseq & seq);
  99         q->ordseq |= seq;
 100
 101         if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
 102                 return;
 103
 104         /*
 105          * Okay, sequence complete.
 106          */
 107         q->ordseq = 0;
 108         rq = q->orig_bar_rq;
 109
 110         if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq)))
 111                 BUG();
 112 }
 113
 114 static void pre_flush_end_io(struct request *rq, int error)
 115 {
 116         elv_completed_request(rq->q, rq);
 117         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
 118 }
 119
 120 static void bar_end_io(struct request *rq, int error)
 121 {
 122         elv_completed_request(rq->q, rq);
 123         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
 124 }
 125
 126 static void post_flush_end_io(struct request *rq, int error)
 127 {
 128         elv_completed_request(rq->q, rq);
 129         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
 130 }
 131
 132 static void queue_flush(struct request_queue *q, unsigned which)
 133 {
 134         struct request *rq;
 135         rq_end_io_fn *end_io;
 136
 137         if (which == QUEUE_ORDERED_DO_PREFLUSH) {
 138                 rq = &q->pre_flush_rq;
 139                 end_io = pre_flush_end_io;
 140         } else {
 141                 rq = &q->post_flush_rq;
 142                 end_io = post_flush_end_io;
 143         }
 144
 145         blk_rq_init(q, rq);
 146         rq->cmd_flags = REQ_HARDBARRIER;
 147         rq->rq_disk = q->bar_rq.rq_disk;
 148         rq->end_io = end_io;
 149         q->prepare_flush_fn(q, rq);
 150
 151         elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
 152 }
 153
 154 static inline struct request *start_ordered(struct request_queue *q,
 155                                             struct request *rq)
 156 {
 157         q->orderr = 0;
 158         q->ordered = q->next_ordered;
 159         q->ordseq |= QUEUE_ORDSEQ_STARTED;
 160
 161         /* stash away the original request */
 162         elv_dequeue_request(q, rq);
 163         q->orig_bar_rq = rq;
 164         rq = NULL;
 165
 166         /*
 167          * Queue ordered sequence.  As we stack them at the head, we
 168          * need to queue in reverse order.  Note that we rely on that
 169          * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
 170          * request gets inbetween ordered sequence. If this request is
 171          * an empty barrier, we don't need to do a postflush ever since
 172          * there will be no data written between the pre and post flush.
 173          * Hence a single flush will suffice.
 174          */
 175         if ((q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) &&
 176             !blk_empty_barrier(q->orig_bar_rq)) {
 177                 queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
 178                 rq = &q->post_flush_rq;
 179         } else
 180                 q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
 181
 182         if (q->ordered & QUEUE_ORDERED_DO_BAR) {
 183                 rq = &q->bar_rq;
 184
 185                 /* initialize proxy request and queue it */
 186                 blk_rq_init(q, rq);
 187                 if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
 188                         rq->cmd_flags |= REQ_RW;
 189                 if (q->ordered & QUEUE_ORDERED_DO_FUA)
 190                         rq->cmd_flags |= REQ_FUA;
 191                 init_request_from_bio(rq, q->orig_bar_rq->bio);
 192                 rq->end_io = bar_end_io;
 193
 194                 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
 195         } else
 196                 q->ordseq |= QUEUE_ORDSEQ_BAR;
 197
 198         if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
 199                 queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
 200                 rq = &q->pre_flush_rq;
 201         } else
 202                 q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
 203
 204         if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && q->in_flight)
 205                 rq = NULL;
 206         else
 207                 q->ordseq |= QUEUE_ORDSEQ_DRAIN;
 208
 209         return rq;
 210 }
 211
 212 int blk_do_ordered(struct request_queue *q, struct request **rqp)
 213 {
 214         struct request *rq = *rqp;
 215         const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
 216
 217         if (!q->ordseq) {
 218                 if (!is_barrier)
 219                         return 1;
 220
 221                 if (q->next_ordered != QUEUE_ORDERED_NONE) {
 222                         *rqp = start_ordered(q, rq);
 223                         return 1;
 224                 } else {
 225                         /*
 226                          * Queue ordering not supported.  Terminate
 227                          * with prejudice.
 228                          */
 229                         elv_dequeue_request(q, rq);
 230                         if (__blk_end_request(rq, -EOPNOTSUPP,
 231                                               blk_rq_bytes(rq)))
 232                                 BUG();
 233                         *rqp = NULL;
 234                         return 0;
 235                 }
 236         }
 237
 238         /*
 239          * Ordered sequence in progress
 240          */
 241
 242         /* Special requests are not subject to ordering rules. */
 243         if (!blk_fs_request(rq) &&
 244             rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
 245                 return 1;
 246
 247         if (q->ordered & QUEUE_ORDERED_BY_TAG) {
 248                 /* Ordered by tag.  Blocking the next barrier is enough. */
 249                 if (is_barrier && rq != &q->bar_rq)
 250                         *rqp = NULL;
 251         } else {
 252                 /* Ordered by draining.  Wait for turn. */
 253                 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
 254                 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
 255                         *rqp = NULL;
 256         }
 257
 258         return 1;
 259 }
 260
 261 static void bio_end_empty_barrier(struct bio *bio, int err)
 262 {
 263         if (err) {
 264                 if (err == -EOPNOTSUPP)
 265                         set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
 266                 clear_bit(BIO_UPTODATE, &bio->bi_flags);
 267         }
 268
 269         complete(bio->bi_private);
 270 }
 271
 272 /**
 273  * blkdev_issue_flush - queue a flush
 274  * @bdev:       blockdev to issue flush for
 275  * @error_sector:       error sector
 276  *
 277  * Description:
 278  *    Issue a flush for the block device in question. Caller can supply
 279  *    room for storing the error offset in case of a flush error, if they
 280  *    wish to.  Caller must run wait_for_completion() on its own.
 281  */
 282 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
 283 {
 284         DECLARE_COMPLETION_ONSTACK(wait);
 285         struct request_queue *q;
 286         struct bio *bio;
 287         int ret;
 288
 289         if (bdev->bd_disk == NULL)
 290                 return -ENXIO;
 291
 292         q = bdev_get_queue(bdev);
 293         if (!q)
 294                 return -ENXIO;
 295
 296         bio = bio_alloc(GFP_KERNEL, 0);
 297         if (!bio)
 298                 return -ENOMEM;
 299
 300         bio->bi_end_io = bio_end_empty_barrier;
 301         bio->bi_private = &wait;
 302         bio->bi_bdev = bdev;
 303         submit_bio(WRITE_BARRIER, bio);
 304
 305         wait_for_completion(&wait);
 306
 307         /*
 308          * The driver must store the error location in ->bi_sector, if
 309          * it supports it. For non-stacked drivers, this should be copied
 310          * from rq->sector.
 311          */
 312         if (error_sector)
 313                 *error_sector = bio->bi_sector;
 314
 315         ret = 0;
 316         if (bio_flagged(bio, BIO_EOPNOTSUPP))
 317                 ret = -EOPNOTSUPP;
 318         else if (!bio_flagged(bio, BIO_UPTODATE))
 319                 ret = -EIO;
 320
 321         bio_put(bio);
 322         return ret;
 323 }
 324 EXPORT_SYMBOL(blkdev_issue_flush);
 325
 326 static void blkdev_discard_end_io(struct bio *bio, int err)
 327 {
 328         if (err) {
 329                 if (err == -EOPNOTSUPP)
 330                         set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
 331                 clear_bit(BIO_UPTODATE, &bio->bi_flags);
 332         }
 333
 334         bio_put(bio);
 335 }
 336
 337 /**
 338  * blkdev_issue_discard - queue a discard
 339  * @bdev:       blockdev to issue discard for
 340  * @sector:     start sector
 341  * @nr_sects:   number of sectors to discard
 342  * @gfp_mask:   memory allocation flags (for bio_alloc)
 343  *
 344  * Description:
 345  *    Issue a discard request for the sectors in question. Does not wait.
 346  */
 347 int blkdev_issue_discard(struct block_device *bdev,
 348                          sector_t sector, sector_t nr_sects, gfp_t gfp_mask)
 349 {
 350         struct request_queue *q;
 351         struct bio *bio;
 352         int ret = 0;
 353
 354         if (bdev->bd_disk == NULL)
 355                 return -ENXIO;
 356
 357         q = bdev_get_queue(bdev);
 358         if (!q)
 359                 return -ENXIO;
 360
 361         if (!q->prepare_discard_fn)
 362                 return -EOPNOTSUPP;
 363
 364         while (nr_sects && !ret) {
 365                 bio = bio_alloc(gfp_mask, 0);
 366                 if (!bio)
 367                         return -ENOMEM;
 368
 369                 bio->bi_end_io = blkdev_discard_end_io;
 370                 bio->bi_bdev = bdev;
 371
 372                 bio->bi_sector = sector;
 373
 374                 if (nr_sects > q->max_hw_sectors) {
 375                         bio->bi_size = q->max_hw_sectors << 9;
 376                         nr_sects -= q->max_hw_sectors;
 377                         sector += q->max_hw_sectors;
 378                 } else {
 379                         bio->bi_size = nr_sects << 9;
 380                         nr_sects = 0;
 381                 }
 382                 bio_get(bio);
 383                 submit_bio(DISCARD_BARRIER, bio);
 384
 385                 /* Check if it failed immediately */
 386                 if (bio_flagged(bio, BIO_EOPNOTSUPP))
 387                         ret = -EOPNOTSUPP;
 388                 else if (!bio_flagged(bio, BIO_UPTODATE))
 389                         ret = -EIO;
 390                 bio_put(bio);
 391         }
 392         return ret;
 393 }
 394 EXPORT_SYMBOL(blkdev_issue_discard);