2 * Functions related to setting various queue properties from drivers
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/init.h>
8 #include <linux/blkdev.h>
9 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
13 unsigned long blk_max_low_pfn;
14 EXPORT_SYMBOL(blk_max_low_pfn);
16 unsigned long blk_max_pfn;
19 * blk_queue_prep_rq - set a prepare_request function for queue
21 * @pfn: prepare_request function
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.
29 void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
33 EXPORT_SYMBOL(blk_queue_prep_rq);
36 * blk_queue_set_discard - set a discard_sectors function for queue
38 * @dfn: prepare_discard function
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
46 void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn)
48 q->prepare_discard_fn = dfn;
50 EXPORT_SYMBOL(blk_queue_set_discard);
53 * blk_queue_merge_bvec - set a merge_bvec function for queue
55 * @mbfn: merge_bvec_fn
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
68 void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
70 q->merge_bvec_fn = mbfn;
72 EXPORT_SYMBOL(blk_queue_merge_bvec);
74 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
76 q->softirq_done_fn = fn;
78 EXPORT_SYMBOL(blk_queue_softirq_done);
80 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
82 q->rq_timeout = timeout;
84 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
86 void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
88 q->rq_timed_out_fn = fn;
90 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
92 void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
96 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
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
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().
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.
120 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
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 blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK);
129 blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
131 q->make_request_fn = mfn;
132 q->backing_dev_info.ra_pages =
133 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
134 q->backing_dev_info.state = 0;
135 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
136 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
137 blk_queue_logical_block_size(q, 512);
138 blk_queue_dma_alignment(q, 511);
139 blk_queue_congestion_threshold(q);
140 q->nr_batching = BLK_BATCH_REQ;
142 q->unplug_thresh = 4; /* hmm */
143 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
144 if (q->unplug_delay == 0)
147 q->unplug_timer.function = blk_unplug_timeout;
148 q->unplug_timer.data = (unsigned long)q;
151 * by default assume old behaviour and bounce for any highmem page
153 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
155 EXPORT_SYMBOL(blk_queue_make_request);
158 * blk_queue_bounce_limit - set bounce buffer limit for queue
159 * @q: the request queue for the device
160 * @dma_mask: the maximum address the device can handle
163 * Different hardware can have different requirements as to what pages
164 * it can do I/O directly to. A low level driver can call
165 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
166 * buffers for doing I/O to pages residing above @dma_mask.
168 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
170 unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
173 q->bounce_gfp = GFP_NOIO;
174 #if BITS_PER_LONG == 64
176 * Assume anything <= 4GB can be handled by IOMMU. Actually
177 * some IOMMUs can handle everything, but I don't know of a
178 * way to test this here.
180 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
182 q->bounce_pfn = max_low_pfn;
184 if (b_pfn < blk_max_low_pfn)
186 q->bounce_pfn = b_pfn;
189 init_emergency_isa_pool();
190 q->bounce_gfp = GFP_NOIO | GFP_DMA;
191 q->bounce_pfn = b_pfn;
194 EXPORT_SYMBOL(blk_queue_bounce_limit);
197 * blk_queue_max_sectors - set max sectors for a request for this queue
198 * @q: the request queue for the device
199 * @max_sectors: max sectors in the usual 512b unit
202 * Enables a low level driver to set an upper limit on the size of
205 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
207 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
208 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
209 printk(KERN_INFO "%s: set to minimum %d\n",
210 __func__, max_sectors);
213 if (BLK_DEF_MAX_SECTORS > max_sectors)
214 q->max_hw_sectors = q->max_sectors = max_sectors;
216 q->max_sectors = BLK_DEF_MAX_SECTORS;
217 q->max_hw_sectors = max_sectors;
220 EXPORT_SYMBOL(blk_queue_max_sectors);
222 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_sectors)
224 if (BLK_DEF_MAX_SECTORS > max_sectors)
225 q->max_hw_sectors = BLK_DEF_MAX_SECTORS;
227 q->max_hw_sectors = max_sectors;
229 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
232 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
233 * @q: the request queue for the device
234 * @max_segments: max number of segments
237 * Enables a low level driver to set an upper limit on the number of
238 * physical data segments in a request. This would be the largest sized
239 * scatter list the driver could handle.
241 void blk_queue_max_phys_segments(struct request_queue *q,
242 unsigned short max_segments)
246 printk(KERN_INFO "%s: set to minimum %d\n",
247 __func__, max_segments);
250 q->max_phys_segments = max_segments;
252 EXPORT_SYMBOL(blk_queue_max_phys_segments);
255 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
256 * @q: the request queue for the device
257 * @max_segments: max number of segments
260 * Enables a low level driver to set an upper limit on the number of
261 * hw data segments in a request. This would be the largest number of
262 * address/length pairs the host adapter can actually give at once
265 void blk_queue_max_hw_segments(struct request_queue *q,
266 unsigned short max_segments)
270 printk(KERN_INFO "%s: set to minimum %d\n",
271 __func__, max_segments);
274 q->max_hw_segments = max_segments;
276 EXPORT_SYMBOL(blk_queue_max_hw_segments);
279 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
280 * @q: the request queue for the device
281 * @max_size: max size of segment in bytes
284 * Enables a low level driver to set an upper limit on the size of a
287 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
289 if (max_size < PAGE_CACHE_SIZE) {
290 max_size = PAGE_CACHE_SIZE;
291 printk(KERN_INFO "%s: set to minimum %d\n",
295 q->max_segment_size = max_size;
297 EXPORT_SYMBOL(blk_queue_max_segment_size);
300 * blk_queue_logical_block_size - set logical block size for the queue
301 * @q: the request queue for the device
302 * @size: the logical block size, in bytes
305 * This should be set to the lowest possible block size that the
306 * storage device can address. The default of 512 covers most
309 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
311 q->logical_block_size = size;
313 EXPORT_SYMBOL(blk_queue_logical_block_size);
316 * Returns the minimum that is _not_ zero, unless both are zero.
318 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
321 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
322 * @t: the stacking driver (top)
323 * @b: the underlying device (bottom)
325 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
327 /* zero is "infinity" */
328 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
329 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
330 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask, b->seg_boundary_mask);
332 t->max_phys_segments = min_not_zero(t->max_phys_segments, b->max_phys_segments);
333 t->max_hw_segments = min_not_zero(t->max_hw_segments, b->max_hw_segments);
334 t->max_segment_size = min_not_zero(t->max_segment_size, b->max_segment_size);
335 t->logical_block_size = max(t->logical_block_size, b->logical_block_size);
338 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
340 spin_lock_irqsave(t->queue_lock, flags);
341 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
342 spin_unlock_irqrestore(t->queue_lock, flags);
345 EXPORT_SYMBOL(blk_queue_stack_limits);
348 * blk_queue_dma_pad - set pad mask
349 * @q: the request queue for the device
354 * Appending pad buffer to a request modifies the last entry of a
355 * scatter list such that it includes the pad buffer.
357 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
359 q->dma_pad_mask = mask;
361 EXPORT_SYMBOL(blk_queue_dma_pad);
364 * blk_queue_update_dma_pad - update pad mask
365 * @q: the request queue for the device
368 * Update dma pad mask.
370 * Appending pad buffer to a request modifies the last entry of a
371 * scatter list such that it includes the pad buffer.
373 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
375 if (mask > q->dma_pad_mask)
376 q->dma_pad_mask = mask;
378 EXPORT_SYMBOL(blk_queue_update_dma_pad);
381 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
382 * @q: the request queue for the device
383 * @dma_drain_needed: fn which returns non-zero if drain is necessary
384 * @buf: physically contiguous buffer
385 * @size: size of the buffer in bytes
387 * Some devices have excess DMA problems and can't simply discard (or
388 * zero fill) the unwanted piece of the transfer. They have to have a
389 * real area of memory to transfer it into. The use case for this is
390 * ATAPI devices in DMA mode. If the packet command causes a transfer
391 * bigger than the transfer size some HBAs will lock up if there
392 * aren't DMA elements to contain the excess transfer. What this API
393 * does is adjust the queue so that the buf is always appended
394 * silently to the scatterlist.
396 * Note: This routine adjusts max_hw_segments to make room for
397 * appending the drain buffer. If you call
398 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
399 * calling this routine, you must set the limit to one fewer than your
400 * device can support otherwise there won't be room for the drain
403 int blk_queue_dma_drain(struct request_queue *q,
404 dma_drain_needed_fn *dma_drain_needed,
405 void *buf, unsigned int size)
407 if (queue_max_hw_segments(q) < 2 || queue_max_phys_segments(q) < 2)
409 /* make room for appending the drain */
410 blk_queue_max_hw_segments(q, queue_max_hw_segments(q) - 1);
411 blk_queue_max_phys_segments(q, queue_max_phys_segments(q) - 1);
412 q->dma_drain_needed = dma_drain_needed;
413 q->dma_drain_buffer = buf;
414 q->dma_drain_size = size;
418 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
421 * blk_queue_segment_boundary - set boundary rules for segment merging
422 * @q: the request queue for the device
423 * @mask: the memory boundary mask
425 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
427 if (mask < PAGE_CACHE_SIZE - 1) {
428 mask = PAGE_CACHE_SIZE - 1;
429 printk(KERN_INFO "%s: set to minimum %lx\n",
433 q->seg_boundary_mask = mask;
435 EXPORT_SYMBOL(blk_queue_segment_boundary);
438 * blk_queue_dma_alignment - set dma length and memory alignment
439 * @q: the request queue for the device
440 * @mask: alignment mask
443 * set required memory and length alignment for direct dma transactions.
444 * this is used when building direct io requests for the queue.
447 void blk_queue_dma_alignment(struct request_queue *q, int mask)
449 q->dma_alignment = mask;
451 EXPORT_SYMBOL(blk_queue_dma_alignment);
454 * blk_queue_update_dma_alignment - update dma length and memory alignment
455 * @q: the request queue for the device
456 * @mask: alignment mask
459 * update required memory and length alignment for direct dma transactions.
460 * If the requested alignment is larger than the current alignment, then
461 * the current queue alignment is updated to the new value, otherwise it
462 * is left alone. The design of this is to allow multiple objects
463 * (driver, device, transport etc) to set their respective
464 * alignments without having them interfere.
467 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
469 BUG_ON(mask > PAGE_SIZE);
471 if (mask > q->dma_alignment)
472 q->dma_alignment = mask;
474 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
476 static int __init blk_settings_init(void)
478 blk_max_low_pfn = max_low_pfn - 1;
479 blk_max_pfn = max_pfn - 1;
482 subsys_initcall(blk_settings_init);