xref: /openbmc/linux/block/blk-settings.c (revision 9ac8d3fb)
1 /*
2  * Functions related to setting various queue properties from drivers
3  */
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/init.h>
7 #include <linux/bio.h>
8 #include <linux/blkdev.h>
9 #include <linux/bootmem.h>	/* for max_pfn/max_low_pfn */
10 
11 #include "blk.h"
12 
13 unsigned long blk_max_low_pfn;
14 EXPORT_SYMBOL(blk_max_low_pfn);
15 
16 unsigned long blk_max_pfn;
17 
18 /**
19  * blk_queue_prep_rq - set a prepare_request function for queue
20  * @q:		queue
21  * @pfn:	prepare_request function
22  *
23  * It's possible for a queue to register a prepare_request callback which
24  * is invoked before the request is handed to the request_fn. The goal of
25  * the function is to prepare a request for I/O, it can be used to build a
26  * cdb from the request data for instance.
27  *
28  */
29 void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
30 {
31 	q->prep_rq_fn = pfn;
32 }
33 EXPORT_SYMBOL(blk_queue_prep_rq);
34 
35 /**
36  * blk_queue_set_discard - set a discard_sectors function for queue
37  * @q:		queue
38  * @dfn:	prepare_discard function
39  *
40  * It's possible for a queue to register a discard callback which is used
41  * to transform a discard request into the appropriate type for the
42  * hardware. If none is registered, then discard requests are failed
43  * with %EOPNOTSUPP.
44  *
45  */
46 void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn)
47 {
48 	q->prepare_discard_fn = dfn;
49 }
50 EXPORT_SYMBOL(blk_queue_set_discard);
51 
52 /**
53  * blk_queue_merge_bvec - set a merge_bvec function for queue
54  * @q:		queue
55  * @mbfn:	merge_bvec_fn
56  *
57  * Usually queues have static limitations on the max sectors or segments that
58  * we can put in a request. Stacking drivers may have some settings that
59  * are dynamic, and thus we have to query the queue whether it is ok to
60  * add a new bio_vec to a bio at a given offset or not. If the block device
61  * has such limitations, it needs to register a merge_bvec_fn to control
62  * the size of bio's sent to it. Note that a block device *must* allow a
63  * single page to be added to an empty bio. The block device driver may want
64  * to use the bio_split() function to deal with these bio's. By default
65  * no merge_bvec_fn is defined for a queue, and only the fixed limits are
66  * honored.
67  */
68 void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
69 {
70 	q->merge_bvec_fn = mbfn;
71 }
72 EXPORT_SYMBOL(blk_queue_merge_bvec);
73 
74 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
75 {
76 	q->softirq_done_fn = fn;
77 }
78 EXPORT_SYMBOL(blk_queue_softirq_done);
79 
80 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
81 {
82 	q->rq_timeout = timeout;
83 }
84 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
85 
86 void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
87 {
88 	q->rq_timed_out_fn = fn;
89 }
90 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
91 
92 void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
93 {
94 	q->lld_busy_fn = fn;
95 }
96 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
97 
98 /**
99  * blk_queue_make_request - define an alternate make_request function for a device
100  * @q:  the request queue for the device to be affected
101  * @mfn: the alternate make_request function
102  *
103  * Description:
104  *    The normal way for &struct bios to be passed to a device
105  *    driver is for them to be collected into requests on a request
106  *    queue, and then to allow the device driver to select requests
107  *    off that queue when it is ready.  This works well for many block
108  *    devices. However some block devices (typically virtual devices
109  *    such as md or lvm) do not benefit from the processing on the
110  *    request queue, and are served best by having the requests passed
111  *    directly to them.  This can be achieved by providing a function
112  *    to blk_queue_make_request().
113  *
114  * Caveat:
115  *    The driver that does this *must* be able to deal appropriately
116  *    with buffers in "highmemory". This can be accomplished by either calling
117  *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
118  *    blk_queue_bounce() to create a buffer in normal memory.
119  **/
120 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
121 {
122 	/*
123 	 * set defaults
124 	 */
125 	q->nr_requests = BLKDEV_MAX_RQ;
126 	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
127 	blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
128 	q->make_request_fn = mfn;
129 	q->backing_dev_info.ra_pages =
130 			(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
131 	q->backing_dev_info.state = 0;
132 	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
133 	blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
134 	blk_queue_hardsect_size(q, 512);
135 	blk_queue_dma_alignment(q, 511);
136 	blk_queue_congestion_threshold(q);
137 	q->nr_batching = BLK_BATCH_REQ;
138 
139 	q->unplug_thresh = 4;		/* hmm */
140 	q->unplug_delay = (3 * HZ) / 1000;	/* 3 milliseconds */
141 	if (q->unplug_delay == 0)
142 		q->unplug_delay = 1;
143 
144 	q->unplug_timer.function = blk_unplug_timeout;
145 	q->unplug_timer.data = (unsigned long)q;
146 
147 	/*
148 	 * by default assume old behaviour and bounce for any highmem page
149 	 */
150 	blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
151 }
152 EXPORT_SYMBOL(blk_queue_make_request);
153 
154 /**
155  * blk_queue_bounce_limit - set bounce buffer limit for queue
156  * @q:  the request queue for the device
157  * @dma_addr:   bus address limit
158  *
159  * Description:
160  *    Different hardware can have different requirements as to what pages
161  *    it can do I/O directly to. A low level driver can call
162  *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
163  *    buffers for doing I/O to pages residing above @dma_addr.
164  **/
165 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr)
166 {
167 	unsigned long b_pfn = dma_addr >> PAGE_SHIFT;
168 	int dma = 0;
169 
170 	q->bounce_gfp = GFP_NOIO;
171 #if BITS_PER_LONG == 64
172 	/* Assume anything <= 4GB can be handled by IOMMU.
173 	   Actually some IOMMUs can handle everything, but I don't
174 	   know of a way to test this here. */
175 	if (b_pfn < (min_t(u64, 0x100000000UL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
176 		dma = 1;
177 	q->bounce_pfn = max_low_pfn;
178 #else
179 	if (b_pfn < blk_max_low_pfn)
180 		dma = 1;
181 	q->bounce_pfn = b_pfn;
182 #endif
183 	if (dma) {
184 		init_emergency_isa_pool();
185 		q->bounce_gfp = GFP_NOIO | GFP_DMA;
186 		q->bounce_pfn = b_pfn;
187 	}
188 }
189 EXPORT_SYMBOL(blk_queue_bounce_limit);
190 
191 /**
192  * blk_queue_max_sectors - set max sectors for a request for this queue
193  * @q:  the request queue for the device
194  * @max_sectors:  max sectors in the usual 512b unit
195  *
196  * Description:
197  *    Enables a low level driver to set an upper limit on the size of
198  *    received requests.
199  **/
200 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
201 {
202 	if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
203 		max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
204 		printk(KERN_INFO "%s: set to minimum %d\n",
205 		       __func__, max_sectors);
206 	}
207 
208 	if (BLK_DEF_MAX_SECTORS > max_sectors)
209 		q->max_hw_sectors = q->max_sectors = max_sectors;
210 	else {
211 		q->max_sectors = BLK_DEF_MAX_SECTORS;
212 		q->max_hw_sectors = max_sectors;
213 	}
214 }
215 EXPORT_SYMBOL(blk_queue_max_sectors);
216 
217 /**
218  * blk_queue_max_phys_segments - set max phys segments for a request for this queue
219  * @q:  the request queue for the device
220  * @max_segments:  max number of segments
221  *
222  * Description:
223  *    Enables a low level driver to set an upper limit on the number of
224  *    physical data segments in a request.  This would be the largest sized
225  *    scatter list the driver could handle.
226  **/
227 void blk_queue_max_phys_segments(struct request_queue *q,
228 				 unsigned short max_segments)
229 {
230 	if (!max_segments) {
231 		max_segments = 1;
232 		printk(KERN_INFO "%s: set to minimum %d\n",
233 		       __func__, max_segments);
234 	}
235 
236 	q->max_phys_segments = max_segments;
237 }
238 EXPORT_SYMBOL(blk_queue_max_phys_segments);
239 
240 /**
241  * blk_queue_max_hw_segments - set max hw segments for a request for this queue
242  * @q:  the request queue for the device
243  * @max_segments:  max number of segments
244  *
245  * Description:
246  *    Enables a low level driver to set an upper limit on the number of
247  *    hw data segments in a request.  This would be the largest number of
248  *    address/length pairs the host adapter can actually give at once
249  *    to the device.
250  **/
251 void blk_queue_max_hw_segments(struct request_queue *q,
252 			       unsigned short max_segments)
253 {
254 	if (!max_segments) {
255 		max_segments = 1;
256 		printk(KERN_INFO "%s: set to minimum %d\n",
257 		       __func__, max_segments);
258 	}
259 
260 	q->max_hw_segments = max_segments;
261 }
262 EXPORT_SYMBOL(blk_queue_max_hw_segments);
263 
264 /**
265  * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
266  * @q:  the request queue for the device
267  * @max_size:  max size of segment in bytes
268  *
269  * Description:
270  *    Enables a low level driver to set an upper limit on the size of a
271  *    coalesced segment
272  **/
273 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
274 {
275 	if (max_size < PAGE_CACHE_SIZE) {
276 		max_size = PAGE_CACHE_SIZE;
277 		printk(KERN_INFO "%s: set to minimum %d\n",
278 		       __func__, max_size);
279 	}
280 
281 	q->max_segment_size = max_size;
282 }
283 EXPORT_SYMBOL(blk_queue_max_segment_size);
284 
285 /**
286  * blk_queue_hardsect_size - set hardware sector size for the queue
287  * @q:  the request queue for the device
288  * @size:  the hardware sector size, in bytes
289  *
290  * Description:
291  *   This should typically be set to the lowest possible sector size
292  *   that the hardware can operate on (possible without reverting to
293  *   even internal read-modify-write operations). Usually the default
294  *   of 512 covers most hardware.
295  **/
296 void blk_queue_hardsect_size(struct request_queue *q, unsigned short size)
297 {
298 	q->hardsect_size = size;
299 }
300 EXPORT_SYMBOL(blk_queue_hardsect_size);
301 
302 /*
303  * Returns the minimum that is _not_ zero, unless both are zero.
304  */
305 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
306 
307 /**
308  * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
309  * @t:	the stacking driver (top)
310  * @b:  the underlying device (bottom)
311  **/
312 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
313 {
314 	/* zero is "infinity" */
315 	t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
316 	t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
317 
318 	t->max_phys_segments = min(t->max_phys_segments, b->max_phys_segments);
319 	t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments);
320 	t->max_segment_size = min(t->max_segment_size, b->max_segment_size);
321 	t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
322 	if (!t->queue_lock)
323 		WARN_ON_ONCE(1);
324 	else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
325 		unsigned long flags;
326 		spin_lock_irqsave(t->queue_lock, flags);
327 		queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
328 		spin_unlock_irqrestore(t->queue_lock, flags);
329 	}
330 }
331 EXPORT_SYMBOL(blk_queue_stack_limits);
332 
333 /**
334  * blk_queue_dma_pad - set pad mask
335  * @q:     the request queue for the device
336  * @mask:  pad mask
337  *
338  * Set dma pad mask.
339  *
340  * Appending pad buffer to a request modifies the last entry of a
341  * scatter list such that it includes the pad buffer.
342  **/
343 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
344 {
345 	q->dma_pad_mask = mask;
346 }
347 EXPORT_SYMBOL(blk_queue_dma_pad);
348 
349 /**
350  * blk_queue_update_dma_pad - update pad mask
351  * @q:     the request queue for the device
352  * @mask:  pad mask
353  *
354  * Update dma pad mask.
355  *
356  * Appending pad buffer to a request modifies the last entry of a
357  * scatter list such that it includes the pad buffer.
358  **/
359 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
360 {
361 	if (mask > q->dma_pad_mask)
362 		q->dma_pad_mask = mask;
363 }
364 EXPORT_SYMBOL(blk_queue_update_dma_pad);
365 
366 /**
367  * blk_queue_dma_drain - Set up a drain buffer for excess dma.
368  * @q:  the request queue for the device
369  * @dma_drain_needed: fn which returns non-zero if drain is necessary
370  * @buf:	physically contiguous buffer
371  * @size:	size of the buffer in bytes
372  *
373  * Some devices have excess DMA problems and can't simply discard (or
374  * zero fill) the unwanted piece of the transfer.  They have to have a
375  * real area of memory to transfer it into.  The use case for this is
376  * ATAPI devices in DMA mode.  If the packet command causes a transfer
377  * bigger than the transfer size some HBAs will lock up if there
378  * aren't DMA elements to contain the excess transfer.  What this API
379  * does is adjust the queue so that the buf is always appended
380  * silently to the scatterlist.
381  *
382  * Note: This routine adjusts max_hw_segments to make room for
383  * appending the drain buffer.  If you call
384  * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
385  * calling this routine, you must set the limit to one fewer than your
386  * device can support otherwise there won't be room for the drain
387  * buffer.
388  */
389 int blk_queue_dma_drain(struct request_queue *q,
390 			       dma_drain_needed_fn *dma_drain_needed,
391 			       void *buf, unsigned int size)
392 {
393 	if (q->max_hw_segments < 2 || q->max_phys_segments < 2)
394 		return -EINVAL;
395 	/* make room for appending the drain */
396 	--q->max_hw_segments;
397 	--q->max_phys_segments;
398 	q->dma_drain_needed = dma_drain_needed;
399 	q->dma_drain_buffer = buf;
400 	q->dma_drain_size = size;
401 
402 	return 0;
403 }
404 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
405 
406 /**
407  * blk_queue_segment_boundary - set boundary rules for segment merging
408  * @q:  the request queue for the device
409  * @mask:  the memory boundary mask
410  **/
411 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
412 {
413 	if (mask < PAGE_CACHE_SIZE - 1) {
414 		mask = PAGE_CACHE_SIZE - 1;
415 		printk(KERN_INFO "%s: set to minimum %lx\n",
416 		       __func__, mask);
417 	}
418 
419 	q->seg_boundary_mask = mask;
420 }
421 EXPORT_SYMBOL(blk_queue_segment_boundary);
422 
423 /**
424  * blk_queue_dma_alignment - set dma length and memory alignment
425  * @q:     the request queue for the device
426  * @mask:  alignment mask
427  *
428  * description:
429  *    set required memory and length alignment for direct dma transactions.
430  *    this is used when buiding direct io requests for the queue.
431  *
432  **/
433 void blk_queue_dma_alignment(struct request_queue *q, int mask)
434 {
435 	q->dma_alignment = mask;
436 }
437 EXPORT_SYMBOL(blk_queue_dma_alignment);
438 
439 /**
440  * blk_queue_update_dma_alignment - update dma length and memory alignment
441  * @q:     the request queue for the device
442  * @mask:  alignment mask
443  *
444  * description:
445  *    update required memory and length alignment for direct dma transactions.
446  *    If the requested alignment is larger than the current alignment, then
447  *    the current queue alignment is updated to the new value, otherwise it
448  *    is left alone.  The design of this is to allow multiple objects
449  *    (driver, device, transport etc) to set their respective
450  *    alignments without having them interfere.
451  *
452  **/
453 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
454 {
455 	BUG_ON(mask > PAGE_SIZE);
456 
457 	if (mask > q->dma_alignment)
458 		q->dma_alignment = mask;
459 }
460 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
461 
462 static int __init blk_settings_init(void)
463 {
464 	blk_max_low_pfn = max_low_pfn - 1;
465 	blk_max_pfn = max_pfn - 1;
466 	return 0;
467 }
468 subsys_initcall(blk_settings_init);
469