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) {
29 printk(KERN_ERR "%s: prepare_flush_fn required\n",
30 __FUNCTION__);
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 }
51 EXPORT_SYMBOL(blk_queue_ordered);
52
53 /*
54 * Cache flushing for ordered writes handling
55 */
56 inline unsigned blk_ordered_cur_seq(struct request_queue *q)
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
146 rq->cmd_flags = REQ_HARDBARRIER;
147 rq_init(q, rq);
148 rq->elevator_private = NULL;
149 rq->elevator_private2 = NULL;
150 rq->rq_disk = q->bar_rq.rq_disk;
151 rq->end_io = end_io;
152 q->prepare_flush_fn(q, rq);
153
154 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
155 }
156
157 static inline struct request *start_ordered(struct request_queue *q,
158 struct request *rq)
159 {
160 q->orderr = 0;
161 q->ordered = q->next_ordered;
162 q->ordseq |= QUEUE_ORDSEQ_STARTED;
163
164 /*
165 * Prep proxy barrier request.
166 */
167 blkdev_dequeue_request(rq);
168 q->orig_bar_rq = rq;
169 rq = &q->bar_rq;
170 rq->cmd_flags = 0;
171 rq_init(q, rq);
172 if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
173 rq->cmd_flags |= REQ_RW;
174 if (q->ordered & QUEUE_ORDERED_FUA)
175 rq->cmd_flags |= REQ_FUA;
176 rq->elevator_private = NULL;
177 rq->elevator_private2 = NULL;
178 init_request_from_bio(rq, q->orig_bar_rq->bio);
179 rq->end_io = bar_end_io;
180
181 /*
182 * Queue ordered sequence. As we stack them at the head, we
183 * need to queue in reverse order. Note that we rely on that
184 * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
185 * request gets inbetween ordered sequence. If this request is
186 * an empty barrier, we don't need to do a postflush ever since
187 * there will be no data written between the pre and post flush.
188 * Hence a single flush will suffice.
189 */
190 if ((q->ordered & QUEUE_ORDERED_POSTFLUSH) && !blk_empty_barrier(rq))
191 queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
192 else
193 q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
194
195 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
196
197 if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
198 queue_flush(q, QUEUE_ORDERED_PREFLUSH);
199 rq = &q->pre_flush_rq;
200 } else
201 q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
202
203 if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
204 q->ordseq |= QUEUE_ORDSEQ_DRAIN;
205 else
206 rq = NULL;
207
208 return rq;
209 }
210
211 int blk_do_ordered(struct request_queue *q, struct request **rqp)
212 {
213 struct request *rq = *rqp;
214 const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
215
216 if (!q->ordseq) {
217 if (!is_barrier)
218 return 1;
219
220 if (q->next_ordered != QUEUE_ORDERED_NONE) {
221 *rqp = start_ordered(q, rq);
222 return 1;
223 } else {
224 /*
225 * This can happen when the queue switches to
226 * ORDERED_NONE while this request is on it.
227 */
228 blkdev_dequeue_request(rq);
229 if (__blk_end_request(rq, -EOPNOTSUPP,
230 blk_rq_bytes(rq)))
231 BUG();
232 *rqp = NULL;
233 return 0;
234 }
235 }
236
237 /*
238 * Ordered sequence in progress
239 */
240
241 /* Special requests are not subject to ordering rules. */
242 if (!blk_fs_request(rq) &&
243 rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
244 return 1;
245
246 if (q->ordered & QUEUE_ORDERED_TAG) {
247 /* Ordered by tag. Blocking the next barrier is enough. */
248 if (is_barrier && rq != &q->bar_rq)
249 *rqp = NULL;
250 } else {
251 /* Ordered by draining. Wait for turn. */
252 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
253 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
254 *rqp = NULL;
255 }
256
257 return 1;
258 }
259
260 static void bio_end_empty_barrier(struct bio *bio, int err)
261 {
262 if (err) {
263 if (err == -EOPNOTSUPP)
264 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
265 clear_bit(BIO_UPTODATE, &bio->bi_flags);
266 }
267
268 complete(bio->bi_private);
269 }
270
271 /**
272 * blkdev_issue_flush - queue a flush
273 * @bdev: blockdev to issue flush for
274 * @error_sector: error sector
275 *
276 * Description:
277 * Issue a flush for the block device in question. Caller can supply
278 * room for storing the error offset in case of a flush error, if they
279 * wish to. Caller must run wait_for_completion() on its own.
280 */
281 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
282 {
283 DECLARE_COMPLETION_ONSTACK(wait);
284 struct request_queue *q;
285 struct bio *bio;
286 int ret;
287
288 if (bdev->bd_disk == NULL)
289 return -ENXIO;
290
291 q = bdev_get_queue(bdev);
292 if (!q)
293 return -ENXIO;
294
295 bio = bio_alloc(GFP_KERNEL, 0);
296 if (!bio)
297 return -ENOMEM;
298
299 bio->bi_end_io = bio_end_empty_barrier;
300 bio->bi_private = &wait;
301 bio->bi_bdev = bdev;
302 submit_bio(1 << BIO_RW_BARRIER, bio);
303
304 wait_for_completion(&wait);
305
306 /*
307 * The driver must store the error location in ->bi_sector, if
308 * it supports it. For non-stacked drivers, this should be copied
309 * from rq->sector.
310 */
311 if (error_sector)
312 *error_sector = bio->bi_sector;
313
314 ret = 0;
315 if (bio_flagged(bio, BIO_EOPNOTSUPP))
316 ret = -EOPNOTSUPP;
317 else if (!bio_flagged(bio, BIO_UPTODATE))
318 ret = -EIO;
319
320 bio_put(bio);
321 return ret;
322 }
323 EXPORT_SYMBOL(blkdev_issue_flush);
324
|
This page was automatically generated by the
LXR engine.
|