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 bool 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 false;
103
104 /*
105 * Okay, sequence complete.
106 */
107 q->ordseq = 0;
108 rq = q->orig_bar_rq;
109 __blk_end_request_all(rq, q->orderr);
110 return true;
111 }
112
113 static void pre_flush_end_io(struct request *rq, int error)
114 {
115 elv_completed_request(rq->q, rq);
116 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
117 }
118
119 static void bar_end_io(struct request *rq, int error)
120 {
121 elv_completed_request(rq->q, rq);
122 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
123 }
124
125 static void post_flush_end_io(struct request *rq, int error)
126 {
127 elv_completed_request(rq->q, rq);
128 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
129 }
130
131 static void queue_flush(struct request_queue *q, unsigned which)
132 {
133 struct request *rq;
134 rq_end_io_fn *end_io;
135
136 if (which == QUEUE_ORDERED_DO_PREFLUSH) {
137 rq = &q->pre_flush_rq;
138 end_io = pre_flush_end_io;
139 } else {
140 rq = &q->post_flush_rq;
141 end_io = post_flush_end_io;
142 }
143
144 blk_rq_init(q, rq);
145 rq->cmd_flags = REQ_HARDBARRIER;
146 rq->rq_disk = q->bar_rq.rq_disk;
147 rq->end_io = end_io;
148 q->prepare_flush_fn(q, rq);
149
150 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
151 }
152
153 static inline bool start_ordered(struct request_queue *q, struct request **rqp)
154 {
155 struct request *rq = *rqp;
156 unsigned skip = 0;
157
158 q->orderr = 0;
159 q->ordered = q->next_ordered;
160 q->ordseq |= QUEUE_ORDSEQ_STARTED;
161
162 /*
163 * For an empty barrier, there's no actual BAR request, which
164 * in turn makes POSTFLUSH unnecessary. Mask them off.
165 */
166 if (!blk_rq_sectors(rq)) {
167 q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
168 QUEUE_ORDERED_DO_POSTFLUSH);
169 /*
170 * Empty barrier on a write-through device w/ ordered
171 * tag has no command to issue and without any command
172 * to issue, ordering by tag can't be used. Drain
173 * instead.
174 */
175 if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
176 !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
177 q->ordered &= ~QUEUE_ORDERED_BY_TAG;
178 q->ordered |= QUEUE_ORDERED_BY_DRAIN;
179 }
180 }
181
182 /* stash away the original request */
183 blk_dequeue_request(rq);
184 q->orig_bar_rq = rq;
185 rq = NULL;
186
187 /*
188 * Queue ordered sequence. As we stack them at the head, we
189 * need to queue in reverse order. Note that we rely on that
190 * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
191 * request gets inbetween ordered sequence.
192 */
193 if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) {
194 queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
195 rq = &q->post_flush_rq;
196 } else
197 skip |= QUEUE_ORDSEQ_POSTFLUSH;
198
199 if (q->ordered & QUEUE_ORDERED_DO_BAR) {
200 rq = &q->bar_rq;
201
202 /* initialize proxy request and queue it */
203 blk_rq_init(q, rq);
204 if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
205 rq->cmd_flags |= REQ_RW;
206 if (q->ordered & QUEUE_ORDERED_DO_FUA)
207 rq->cmd_flags |= REQ_FUA;
208 init_request_from_bio(rq, q->orig_bar_rq->bio);
209 rq->end_io = bar_end_io;
210
211 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
212 } else
213 skip |= QUEUE_ORDSEQ_BAR;
214
215 if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
216 queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
217 rq = &q->pre_flush_rq;
218 } else
219 skip |= QUEUE_ORDSEQ_PREFLUSH;
220
221 if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
222 rq = NULL;
223 else
224 skip |= QUEUE_ORDSEQ_DRAIN;
225
226 *rqp = rq;
227
228 /*
229 * Complete skipped sequences. If whole sequence is complete,
230 * return false to tell elevator that this request is gone.
231 */
232 return !blk_ordered_complete_seq(q, skip, 0);
233 }
234
235 bool blk_do_ordered(struct request_queue *q, struct request **rqp)
236 {
237 struct request *rq = *rqp;
238 const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
239
240 if (!q->ordseq) {
241 if (!is_barrier)
242 return true;
243
244 if (q->next_ordered != QUEUE_ORDERED_NONE)
245 return start_ordered(q, rqp);
246 else {
247 /*
248 * Queue ordering not supported. Terminate
249 * with prejudice.
250 */
251 blk_dequeue_request(rq);
252 __blk_end_request_all(rq, -EOPNOTSUPP);
253 *rqp = NULL;
254 return false;
255 }
256 }
257
258 /*
259 * Ordered sequence in progress
260 */
261
262 /* Special requests are not subject to ordering rules. */
263 if (!blk_fs_request(rq) &&
264 rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
265 return true;
266
267 if (q->ordered & QUEUE_ORDERED_BY_TAG) {
268 /* Ordered by tag. Blocking the next barrier is enough. */
269 if (is_barrier && rq != &q->bar_rq)
270 *rqp = NULL;
271 } else {
272 /* Ordered by draining. Wait for turn. */
273 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
274 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
275 *rqp = NULL;
276 }
277
278 return true;
279 }
280
281 static void bio_end_empty_barrier(struct bio *bio, int err)
282 {
283 if (err) {
284 if (err == -EOPNOTSUPP)
285 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
286 clear_bit(BIO_UPTODATE, &bio->bi_flags);
287 }
288
289 complete(bio->bi_private);
290 }
291
292 /**
293 * blkdev_issue_flush - queue a flush
294 * @bdev: blockdev to issue flush for
295 * @error_sector: error sector
296 *
297 * Description:
298 * Issue a flush for the block device in question. Caller can supply
299 * room for storing the error offset in case of a flush error, if they
300 * wish to.
301 */
302 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
303 {
304 DECLARE_COMPLETION_ONSTACK(wait);
305 struct request_queue *q;
306 struct bio *bio;
307 int ret;
308
309 if (bdev->bd_disk == NULL)
310 return -ENXIO;
311
312 q = bdev_get_queue(bdev);
313 if (!q)
314 return -ENXIO;
315
316 bio = bio_alloc(GFP_KERNEL, 0);
317 bio->bi_end_io = bio_end_empty_barrier;
318 bio->bi_private = &wait;
319 bio->bi_bdev = bdev;
320 submit_bio(WRITE_BARRIER, bio);
321
322 wait_for_completion(&wait);
323
324 /*
325 * The driver must store the error location in ->bi_sector, if
326 * it supports it. For non-stacked drivers, this should be copied
327 * from blk_rq_pos(rq).
328 */
329 if (error_sector)
330 *error_sector = bio->bi_sector;
331
332 ret = 0;
333 if (bio_flagged(bio, BIO_EOPNOTSUPP))
334 ret = -EOPNOTSUPP;
335 else if (!bio_flagged(bio, BIO_UPTODATE))
336 ret = -EIO;
337
338 bio_put(bio);
339 return ret;
340 }
341 EXPORT_SYMBOL(blkdev_issue_flush);
342
343 static void blkdev_discard_end_io(struct bio *bio, int err)
344 {
345 if (err) {
346 if (err == -EOPNOTSUPP)
347 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
348 clear_bit(BIO_UPTODATE, &bio->bi_flags);
349 }
350
351 bio_put(bio);
352 }
353
354 /**
355 * blkdev_issue_discard - queue a discard
356 * @bdev: blockdev to issue discard for
357 * @sector: start sector
358 * @nr_sects: number of sectors to discard
359 * @gfp_mask: memory allocation flags (for bio_alloc)
360 *
361 * Description:
362 * Issue a discard request for the sectors in question. Does not wait.
363 */
364 int blkdev_issue_discard(struct block_device *bdev,
365 sector_t sector, sector_t nr_sects, gfp_t gfp_mask)
366 {
367 struct request_queue *q;
368 struct bio *bio;
369 int ret = 0;
370
371 if (bdev->bd_disk == NULL)
372 return -ENXIO;
373
374 q = bdev_get_queue(bdev);
375 if (!q)
376 return -ENXIO;
377
378 if (!q->prepare_discard_fn)
379 return -EOPNOTSUPP;
380
381 while (nr_sects && !ret) {
382 bio = bio_alloc(gfp_mask, 0);
383 if (!bio)
384 return -ENOMEM;
385
386 bio->bi_end_io = blkdev_discard_end_io;
387 bio->bi_bdev = bdev;
388
389 bio->bi_sector = sector;
390
391 if (nr_sects > queue_max_hw_sectors(q)) {
392 bio->bi_size = queue_max_hw_sectors(q) << 9;
393 nr_sects -= queue_max_hw_sectors(q);
394 sector += queue_max_hw_sectors(q);
395 } else {
396 bio->bi_size = nr_sects << 9;
397 nr_sects = 0;
398 }
399 bio_get(bio);
400 submit_bio(DISCARD_BARRIER, bio);
401
402 /* Check if it failed immediately */
403 if (bio_flagged(bio, BIO_EOPNOTSUPP))
404 ret = -EOPNOTSUPP;
405 else if (!bio_flagged(bio, BIO_UPTODATE))
406 ret = -EIO;
407 bio_put(bio);
408 }
409 return ret;
410 }
411 EXPORT_SYMBOL(blkdev_issue_discard);
412
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