Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 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 (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) && |
| 28 | prepare_flush_fn == NULL) { |
Jens Axboe | 6728cb0 | 2008-01-31 13:03:55 +0100 | [diff] [blame] | 29 | printk(KERN_ERR "%s: prepare_flush_fn required\n", |
| 30 | __FUNCTION__); |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 31 | return -EINVAL; |
| 32 | } |
| 33 | |
| 34 | if (ordered != QUEUE_ORDERED_NONE && |
| 35 | ordered != QUEUE_ORDERED_DRAIN && |
| 36 | ordered != QUEUE_ORDERED_DRAIN_FLUSH && |
| 37 | ordered != QUEUE_ORDERED_DRAIN_FUA && |
| 38 | ordered != QUEUE_ORDERED_TAG && |
| 39 | ordered != QUEUE_ORDERED_TAG_FLUSH && |
| 40 | ordered != QUEUE_ORDERED_TAG_FUA) { |
| 41 | printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered); |
| 42 | return -EINVAL; |
| 43 | } |
| 44 | |
| 45 | q->ordered = ordered; |
| 46 | q->next_ordered = ordered; |
| 47 | q->prepare_flush_fn = prepare_flush_fn; |
| 48 | |
| 49 | return 0; |
| 50 | } |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 51 | EXPORT_SYMBOL(blk_queue_ordered); |
| 52 | |
| 53 | /* |
| 54 | * Cache flushing for ordered writes handling |
| 55 | */ |
Adrian Bunk | 6f6a036 | 2008-04-29 09:49:06 +0200 | [diff] [blame] | 56 | unsigned blk_ordered_cur_seq(struct request_queue *q) |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 57 | { |
| 58 | if (!q->ordseq) |
| 59 | return 0; |
| 60 | return 1 << ffz(q->ordseq); |
| 61 | } |
| 62 | |
| 63 | unsigned blk_ordered_req_seq(struct request *rq) |
| 64 | { |
| 65 | struct request_queue *q = rq->q; |
| 66 | |
| 67 | BUG_ON(q->ordseq == 0); |
| 68 | |
| 69 | if (rq == &q->pre_flush_rq) |
| 70 | return QUEUE_ORDSEQ_PREFLUSH; |
| 71 | if (rq == &q->bar_rq) |
| 72 | return QUEUE_ORDSEQ_BAR; |
| 73 | if (rq == &q->post_flush_rq) |
| 74 | return QUEUE_ORDSEQ_POSTFLUSH; |
| 75 | |
| 76 | /* |
| 77 | * !fs requests don't need to follow barrier ordering. Always |
| 78 | * put them at the front. This fixes the following deadlock. |
| 79 | * |
| 80 | * http://thread.gmane.org/gmane.linux.kernel/537473 |
| 81 | */ |
| 82 | if (!blk_fs_request(rq)) |
| 83 | return QUEUE_ORDSEQ_DRAIN; |
| 84 | |
| 85 | if ((rq->cmd_flags & REQ_ORDERED_COLOR) == |
| 86 | (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR)) |
| 87 | return QUEUE_ORDSEQ_DRAIN; |
| 88 | else |
| 89 | return QUEUE_ORDSEQ_DONE; |
| 90 | } |
| 91 | |
| 92 | void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error) |
| 93 | { |
| 94 | struct request *rq; |
| 95 | |
| 96 | if (error && !q->orderr) |
| 97 | q->orderr = error; |
| 98 | |
| 99 | BUG_ON(q->ordseq & seq); |
| 100 | q->ordseq |= seq; |
| 101 | |
| 102 | if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE) |
| 103 | return; |
| 104 | |
| 105 | /* |
| 106 | * Okay, sequence complete. |
| 107 | */ |
| 108 | q->ordseq = 0; |
| 109 | rq = q->orig_bar_rq; |
| 110 | |
| 111 | if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq))) |
| 112 | BUG(); |
| 113 | } |
| 114 | |
| 115 | static void pre_flush_end_io(struct request *rq, int error) |
| 116 | { |
| 117 | elv_completed_request(rq->q, rq); |
| 118 | blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error); |
| 119 | } |
| 120 | |
| 121 | static void bar_end_io(struct request *rq, int error) |
| 122 | { |
| 123 | elv_completed_request(rq->q, rq); |
| 124 | blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error); |
| 125 | } |
| 126 | |
| 127 | static void post_flush_end_io(struct request *rq, int error) |
| 128 | { |
| 129 | elv_completed_request(rq->q, rq); |
| 130 | blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error); |
| 131 | } |
| 132 | |
| 133 | static void queue_flush(struct request_queue *q, unsigned which) |
| 134 | { |
| 135 | struct request *rq; |
| 136 | rq_end_io_fn *end_io; |
| 137 | |
| 138 | if (which == QUEUE_ORDERED_PREFLUSH) { |
| 139 | rq = &q->pre_flush_rq; |
| 140 | end_io = pre_flush_end_io; |
| 141 | } else { |
| 142 | rq = &q->post_flush_rq; |
| 143 | end_io = post_flush_end_io; |
| 144 | } |
| 145 | |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 146 | rq_init(q, rq); |
FUJITA Tomonori | 1afb20f | 2008-04-25 12:26:28 +0200 | [diff] [blame] | 147 | rq->cmd_flags = REQ_HARDBARRIER; |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 148 | rq->rq_disk = q->bar_rq.rq_disk; |
| 149 | rq->end_io = end_io; |
| 150 | q->prepare_flush_fn(q, rq); |
| 151 | |
| 152 | elv_insert(q, rq, ELEVATOR_INSERT_FRONT); |
| 153 | } |
| 154 | |
| 155 | static inline struct request *start_ordered(struct request_queue *q, |
| 156 | struct request *rq) |
| 157 | { |
| 158 | q->orderr = 0; |
| 159 | q->ordered = q->next_ordered; |
| 160 | q->ordseq |= QUEUE_ORDSEQ_STARTED; |
| 161 | |
| 162 | /* |
| 163 | * Prep proxy barrier request. |
| 164 | */ |
| 165 | blkdev_dequeue_request(rq); |
| 166 | q->orig_bar_rq = rq; |
| 167 | rq = &q->bar_rq; |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 168 | rq_init(q, rq); |
| 169 | if (bio_data_dir(q->orig_bar_rq->bio) == WRITE) |
| 170 | rq->cmd_flags |= REQ_RW; |
| 171 | if (q->ordered & QUEUE_ORDERED_FUA) |
| 172 | rq->cmd_flags |= REQ_FUA; |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 173 | init_request_from_bio(rq, q->orig_bar_rq->bio); |
| 174 | rq->end_io = bar_end_io; |
| 175 | |
| 176 | /* |
| 177 | * Queue ordered sequence. As we stack them at the head, we |
| 178 | * need to queue in reverse order. Note that we rely on that |
| 179 | * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs |
| 180 | * request gets inbetween ordered sequence. If this request is |
| 181 | * an empty barrier, we don't need to do a postflush ever since |
| 182 | * there will be no data written between the pre and post flush. |
| 183 | * Hence a single flush will suffice. |
| 184 | */ |
| 185 | if ((q->ordered & QUEUE_ORDERED_POSTFLUSH) && !blk_empty_barrier(rq)) |
| 186 | queue_flush(q, QUEUE_ORDERED_POSTFLUSH); |
| 187 | else |
| 188 | q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH; |
| 189 | |
| 190 | elv_insert(q, rq, ELEVATOR_INSERT_FRONT); |
| 191 | |
| 192 | if (q->ordered & QUEUE_ORDERED_PREFLUSH) { |
| 193 | queue_flush(q, QUEUE_ORDERED_PREFLUSH); |
| 194 | rq = &q->pre_flush_rq; |
| 195 | } else |
| 196 | q->ordseq |= QUEUE_ORDSEQ_PREFLUSH; |
| 197 | |
| 198 | if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0) |
| 199 | q->ordseq |= QUEUE_ORDSEQ_DRAIN; |
| 200 | else |
| 201 | rq = NULL; |
| 202 | |
| 203 | return rq; |
| 204 | } |
| 205 | |
| 206 | int blk_do_ordered(struct request_queue *q, struct request **rqp) |
| 207 | { |
| 208 | struct request *rq = *rqp; |
| 209 | const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq); |
| 210 | |
| 211 | if (!q->ordseq) { |
| 212 | if (!is_barrier) |
| 213 | return 1; |
| 214 | |
| 215 | if (q->next_ordered != QUEUE_ORDERED_NONE) { |
| 216 | *rqp = start_ordered(q, rq); |
| 217 | return 1; |
| 218 | } else { |
| 219 | /* |
| 220 | * This can happen when the queue switches to |
| 221 | * ORDERED_NONE while this request is on it. |
| 222 | */ |
| 223 | blkdev_dequeue_request(rq); |
| 224 | if (__blk_end_request(rq, -EOPNOTSUPP, |
| 225 | blk_rq_bytes(rq))) |
| 226 | BUG(); |
| 227 | *rqp = NULL; |
| 228 | return 0; |
| 229 | } |
| 230 | } |
| 231 | |
| 232 | /* |
| 233 | * Ordered sequence in progress |
| 234 | */ |
| 235 | |
| 236 | /* Special requests are not subject to ordering rules. */ |
| 237 | if (!blk_fs_request(rq) && |
| 238 | rq != &q->pre_flush_rq && rq != &q->post_flush_rq) |
| 239 | return 1; |
| 240 | |
| 241 | if (q->ordered & QUEUE_ORDERED_TAG) { |
| 242 | /* Ordered by tag. Blocking the next barrier is enough. */ |
| 243 | if (is_barrier && rq != &q->bar_rq) |
| 244 | *rqp = NULL; |
| 245 | } else { |
| 246 | /* Ordered by draining. Wait for turn. */ |
| 247 | WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q)); |
| 248 | if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q)) |
| 249 | *rqp = NULL; |
| 250 | } |
| 251 | |
| 252 | return 1; |
| 253 | } |
| 254 | |
| 255 | static void bio_end_empty_barrier(struct bio *bio, int err) |
| 256 | { |
Jens Axboe | cc66b45 | 2008-03-04 11:47:46 +0100 | [diff] [blame] | 257 | if (err) { |
| 258 | if (err == -EOPNOTSUPP) |
| 259 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 260 | clear_bit(BIO_UPTODATE, &bio->bi_flags); |
Jens Axboe | cc66b45 | 2008-03-04 11:47:46 +0100 | [diff] [blame] | 261 | } |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 262 | |
| 263 | complete(bio->bi_private); |
| 264 | } |
| 265 | |
| 266 | /** |
| 267 | * blkdev_issue_flush - queue a flush |
| 268 | * @bdev: blockdev to issue flush for |
| 269 | * @error_sector: error sector |
| 270 | * |
| 271 | * Description: |
| 272 | * Issue a flush for the block device in question. Caller can supply |
| 273 | * room for storing the error offset in case of a flush error, if they |
| 274 | * wish to. Caller must run wait_for_completion() on its own. |
| 275 | */ |
| 276 | int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector) |
| 277 | { |
| 278 | DECLARE_COMPLETION_ONSTACK(wait); |
| 279 | struct request_queue *q; |
| 280 | struct bio *bio; |
| 281 | int ret; |
| 282 | |
| 283 | if (bdev->bd_disk == NULL) |
| 284 | return -ENXIO; |
| 285 | |
| 286 | q = bdev_get_queue(bdev); |
| 287 | if (!q) |
| 288 | return -ENXIO; |
| 289 | |
| 290 | bio = bio_alloc(GFP_KERNEL, 0); |
| 291 | if (!bio) |
| 292 | return -ENOMEM; |
| 293 | |
| 294 | bio->bi_end_io = bio_end_empty_barrier; |
| 295 | bio->bi_private = &wait; |
| 296 | bio->bi_bdev = bdev; |
| 297 | submit_bio(1 << BIO_RW_BARRIER, bio); |
| 298 | |
| 299 | wait_for_completion(&wait); |
| 300 | |
| 301 | /* |
| 302 | * The driver must store the error location in ->bi_sector, if |
| 303 | * it supports it. For non-stacked drivers, this should be copied |
| 304 | * from rq->sector. |
| 305 | */ |
| 306 | if (error_sector) |
| 307 | *error_sector = bio->bi_sector; |
| 308 | |
| 309 | ret = 0; |
Jens Axboe | cc66b45 | 2008-03-04 11:47:46 +0100 | [diff] [blame] | 310 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
| 311 | ret = -EOPNOTSUPP; |
| 312 | else if (!bio_flagged(bio, BIO_UPTODATE)) |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 313 | ret = -EIO; |
| 314 | |
| 315 | bio_put(bio); |
| 316 | return ret; |
| 317 | } |
Jens Axboe | 86db1e2 | 2008-01-29 14:53:40 +0100 | [diff] [blame] | 318 | EXPORT_SYMBOL(blkdev_issue_flush); |