Root/block/blk-tag.c

1/*
2 * Functions related to tagged command queuing
3 */
4#include <linux/kernel.h>
5#include <linux/module.h>
6#include <linux/bio.h>
7#include <linux/blkdev.h>
8#include <linux/slab.h>
9
10#include "blk.h"
11
12/**
13 * blk_queue_find_tag - find a request by its tag and queue
14 * @q: The request queue for the device
15 * @tag: The tag of the request
16 *
17 * Notes:
18 * Should be used when a device returns a tag and you want to match
19 * it with a request.
20 *
21 * no locks need be held.
22 **/
23struct request *blk_queue_find_tag(struct request_queue *q, int tag)
24{
25    return blk_map_queue_find_tag(q->queue_tags, tag);
26}
27EXPORT_SYMBOL(blk_queue_find_tag);
28
29/**
30 * __blk_free_tags - release a given set of tag maintenance info
31 * @bqt: the tag map to free
32 *
33 * Tries to free the specified @bqt. Returns true if it was
34 * actually freed and false if there are still references using it
35 */
36static int __blk_free_tags(struct blk_queue_tag *bqt)
37{
38    int retval;
39
40    retval = atomic_dec_and_test(&bqt->refcnt);
41    if (retval) {
42        BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
43                            bqt->max_depth);
44
45        kfree(bqt->tag_index);
46        bqt->tag_index = NULL;
47
48        kfree(bqt->tag_map);
49        bqt->tag_map = NULL;
50
51        kfree(bqt);
52    }
53
54    return retval;
55}
56
57/**
58 * __blk_queue_free_tags - release tag maintenance info
59 * @q: the request queue for the device
60 *
61 * Notes:
62 * blk_cleanup_queue() will take care of calling this function, if tagging
63 * has been used. So there's no need to call this directly.
64 **/
65void __blk_queue_free_tags(struct request_queue *q)
66{
67    struct blk_queue_tag *bqt = q->queue_tags;
68
69    if (!bqt)
70        return;
71
72    __blk_free_tags(bqt);
73
74    q->queue_tags = NULL;
75    queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
76}
77
78/**
79 * blk_free_tags - release a given set of tag maintenance info
80 * @bqt: the tag map to free
81 *
82 * For externally managed @bqt frees the map. Callers of this
83 * function must guarantee to have released all the queues that
84 * might have been using this tag map.
85 */
86void blk_free_tags(struct blk_queue_tag *bqt)
87{
88    if (unlikely(!__blk_free_tags(bqt)))
89        BUG();
90}
91EXPORT_SYMBOL(blk_free_tags);
92
93/**
94 * blk_queue_free_tags - release tag maintenance info
95 * @q: the request queue for the device
96 *
97 * Notes:
98 * This is used to disable tagged queuing to a device, yet leave
99 * queue in function.
100 **/
101void blk_queue_free_tags(struct request_queue *q)
102{
103    queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
104}
105EXPORT_SYMBOL(blk_queue_free_tags);
106
107static int
108init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
109{
110    struct request **tag_index;
111    unsigned long *tag_map;
112    int nr_ulongs;
113
114    if (q && depth > q->nr_requests * 2) {
115        depth = q->nr_requests * 2;
116        printk(KERN_ERR "%s: adjusted depth to %d\n",
117               __func__, depth);
118    }
119
120    tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
121    if (!tag_index)
122        goto fail;
123
124    nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
125    tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
126    if (!tag_map)
127        goto fail;
128
129    tags->real_max_depth = depth;
130    tags->max_depth = depth;
131    tags->tag_index = tag_index;
132    tags->tag_map = tag_map;
133
134    return 0;
135fail:
136    kfree(tag_index);
137    return -ENOMEM;
138}
139
140static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
141                           int depth)
142{
143    struct blk_queue_tag *tags;
144
145    tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
146    if (!tags)
147        goto fail;
148
149    if (init_tag_map(q, tags, depth))
150        goto fail;
151
152    atomic_set(&tags->refcnt, 1);
153    return tags;
154fail:
155    kfree(tags);
156    return NULL;
157}
158
159/**
160 * blk_init_tags - initialize the tag info for an external tag map
161 * @depth: the maximum queue depth supported
162 **/
163struct blk_queue_tag *blk_init_tags(int depth)
164{
165    return __blk_queue_init_tags(NULL, depth);
166}
167EXPORT_SYMBOL(blk_init_tags);
168
169/**
170 * blk_queue_init_tags - initialize the queue tag info
171 * @q: the request queue for the device
172 * @depth: the maximum queue depth supported
173 * @tags: the tag to use
174 *
175 * Queue lock must be held here if the function is called to resize an
176 * existing map.
177 **/
178int blk_queue_init_tags(struct request_queue *q, int depth,
179            struct blk_queue_tag *tags)
180{
181    int rc;
182
183    BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
184
185    if (!tags && !q->queue_tags) {
186        tags = __blk_queue_init_tags(q, depth);
187
188        if (!tags)
189            goto fail;
190    } else if (q->queue_tags) {
191        rc = blk_queue_resize_tags(q, depth);
192        if (rc)
193            return rc;
194        queue_flag_set(QUEUE_FLAG_QUEUED, q);
195        return 0;
196    } else
197        atomic_inc(&tags->refcnt);
198
199    /*
200     * assign it, all done
201     */
202    q->queue_tags = tags;
203    queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
204    INIT_LIST_HEAD(&q->tag_busy_list);
205    return 0;
206fail:
207    kfree(tags);
208    return -ENOMEM;
209}
210EXPORT_SYMBOL(blk_queue_init_tags);
211
212/**
213 * blk_queue_resize_tags - change the queueing depth
214 * @q: the request queue for the device
215 * @new_depth: the new max command queueing depth
216 *
217 * Notes:
218 * Must be called with the queue lock held.
219 **/
220int blk_queue_resize_tags(struct request_queue *q, int new_depth)
221{
222    struct blk_queue_tag *bqt = q->queue_tags;
223    struct request **tag_index;
224    unsigned long *tag_map;
225    int max_depth, nr_ulongs;
226
227    if (!bqt)
228        return -ENXIO;
229
230    /*
231     * if we already have large enough real_max_depth. just
232     * adjust max_depth. *NOTE* as requests with tag value
233     * between new_depth and real_max_depth can be in-flight, tag
234     * map can not be shrunk blindly here.
235     */
236    if (new_depth <= bqt->real_max_depth) {
237        bqt->max_depth = new_depth;
238        return 0;
239    }
240
241    /*
242     * Currently cannot replace a shared tag map with a new
243     * one, so error out if this is the case
244     */
245    if (atomic_read(&bqt->refcnt) != 1)
246        return -EBUSY;
247
248    /*
249     * save the old state info, so we can copy it back
250     */
251    tag_index = bqt->tag_index;
252    tag_map = bqt->tag_map;
253    max_depth = bqt->real_max_depth;
254
255    if (init_tag_map(q, bqt, new_depth))
256        return -ENOMEM;
257
258    memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
259    nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
260    memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
261
262    kfree(tag_index);
263    kfree(tag_map);
264    return 0;
265}
266EXPORT_SYMBOL(blk_queue_resize_tags);
267
268/**
269 * blk_queue_end_tag - end tag operations for a request
270 * @q: the request queue for the device
271 * @rq: the request that has completed
272 *
273 * Description:
274 * Typically called when end_that_request_first() returns %0, meaning
275 * all transfers have been done for a request. It's important to call
276 * this function before end_that_request_last(), as that will put the
277 * request back on the free list thus corrupting the internal tag list.
278 *
279 * Notes:
280 * queue lock must be held.
281 **/
282void blk_queue_end_tag(struct request_queue *q, struct request *rq)
283{
284    struct blk_queue_tag *bqt = q->queue_tags;
285    unsigned tag = rq->tag; /* negative tags invalid */
286
287    BUG_ON(tag >= bqt->real_max_depth);
288
289    list_del_init(&rq->queuelist);
290    rq->cmd_flags &= ~REQ_QUEUED;
291    rq->tag = -1;
292
293    if (unlikely(bqt->tag_index[tag] == NULL))
294        printk(KERN_ERR "%s: tag %d is missing\n",
295               __func__, tag);
296
297    bqt->tag_index[tag] = NULL;
298
299    if (unlikely(!test_bit(tag, bqt->tag_map))) {
300        printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
301               __func__, tag);
302        return;
303    }
304    /*
305     * The tag_map bit acts as a lock for tag_index[bit], so we need
306     * unlock memory barrier semantics.
307     */
308    clear_bit_unlock(tag, bqt->tag_map);
309}
310EXPORT_SYMBOL(blk_queue_end_tag);
311
312/**
313 * blk_queue_start_tag - find a free tag and assign it
314 * @q: the request queue for the device
315 * @rq: the block request that needs tagging
316 *
317 * Description:
318 * This can either be used as a stand-alone helper, or possibly be
319 * assigned as the queue &prep_rq_fn (in which case &struct request
320 * automagically gets a tag assigned). Note that this function
321 * assumes that any type of request can be queued! if this is not
322 * true for your device, you must check the request type before
323 * calling this function. The request will also be removed from
324 * the request queue, so it's the drivers responsibility to readd
325 * it if it should need to be restarted for some reason.
326 *
327 * Notes:
328 * queue lock must be held.
329 **/
330int blk_queue_start_tag(struct request_queue *q, struct request *rq)
331{
332    struct blk_queue_tag *bqt = q->queue_tags;
333    unsigned max_depth;
334    int tag;
335
336    if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
337        printk(KERN_ERR
338               "%s: request %p for device [%s] already tagged %d",
339               __func__, rq,
340               rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
341        BUG();
342    }
343
344    /*
345     * Protect against shared tag maps, as we may not have exclusive
346     * access to the tag map.
347     *
348     * We reserve a few tags just for sync IO, since we don't want
349     * to starve sync IO on behalf of flooding async IO.
350     */
351    max_depth = bqt->max_depth;
352    if (!rq_is_sync(rq) && max_depth > 1) {
353        max_depth -= 2;
354        if (!max_depth)
355            max_depth = 1;
356        if (q->in_flight[BLK_RW_ASYNC] > max_depth)
357            return 1;
358    }
359
360    do {
361        tag = find_first_zero_bit(bqt->tag_map, max_depth);
362        if (tag >= max_depth)
363            return 1;
364
365    } while (test_and_set_bit_lock(tag, bqt->tag_map));
366    /*
367     * We need lock ordering semantics given by test_and_set_bit_lock.
368     * See blk_queue_end_tag for details.
369     */
370
371    rq->cmd_flags |= REQ_QUEUED;
372    rq->tag = tag;
373    bqt->tag_index[tag] = rq;
374    blk_start_request(rq);
375    list_add(&rq->queuelist, &q->tag_busy_list);
376    return 0;
377}
378EXPORT_SYMBOL(blk_queue_start_tag);
379
380/**
381 * blk_queue_invalidate_tags - invalidate all pending tags
382 * @q: the request queue for the device
383 *
384 * Description:
385 * Hardware conditions may dictate a need to stop all pending requests.
386 * In this case, we will safely clear the block side of the tag queue and
387 * readd all requests to the request queue in the right order.
388 *
389 * Notes:
390 * queue lock must be held.
391 **/
392void blk_queue_invalidate_tags(struct request_queue *q)
393{
394    struct list_head *tmp, *n;
395
396    list_for_each_safe(tmp, n, &q->tag_busy_list)
397        blk_requeue_request(q, list_entry_rq(tmp));
398}
399EXPORT_SYMBOL(blk_queue_invalidate_tags);
400

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