x86: add uniq_ioapic_id to mpparse_32.c
[sfrench/cifs-2.6.git] / 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 (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);