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);
93 * blk_queue_make_request - define an alternate make_request function for a device
94 * @q: the request queue for the device to be affected
95 * @mfn: the alternate make_request function
98 * The normal way for &struct bios to be passed to a device
99 * driver is for them to be collected into requests on a request
100 * queue, and then to allow the device driver to select requests
101 * off that queue when it is ready. This works well for many block
102 * devices. However some block devices (typically virtual devices
103 * such as md or lvm) do not benefit from the processing on the
104 * request queue, and are served best by having the requests passed
105 * directly to them. This can be achieved by providing a function
106 * to blk_queue_make_request().
109 * The driver that does this *must* be able to deal appropriately
110 * with buffers in "highmemory". This can be accomplished by either calling
111 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
112 * blk_queue_bounce() to create a buffer in normal memory.
114 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
119 q->nr_requests = BLKDEV_MAX_RQ;
120 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
121 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
122 q->make_request_fn = mfn;
123 q->backing_dev_info.ra_pages =
124 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
125 q->backing_dev_info.state = 0;
126 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
127 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
128 blk_queue_hardsect_size(q, 512);
129 blk_queue_dma_alignment(q, 511);
130 blk_queue_congestion_threshold(q);
131 q->nr_batching = BLK_BATCH_REQ;
133 q->unplug_thresh = 4; /* hmm */
134 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
135 if (q->unplug_delay == 0)
138 INIT_WORK(&q->unplug_work, blk_unplug_work);
140 q->unplug_timer.function = blk_unplug_timeout;
141 q->unplug_timer.data = (unsigned long)q;
144 * by default assume old behaviour and bounce for any highmem page
146 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
148 EXPORT_SYMBOL(blk_queue_make_request);
151 * blk_queue_bounce_limit - set bounce buffer limit for queue
152 * @q: the request queue for the device
153 * @dma_addr: bus address limit
156 * Different hardware can have different requirements as to what pages
157 * it can do I/O directly to. A low level driver can call
158 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
159 * buffers for doing I/O to pages residing above @dma_addr.
161 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr)
163 unsigned long b_pfn = dma_addr >> PAGE_SHIFT;
166 q->bounce_gfp = GFP_NOIO;
167 #if BITS_PER_LONG == 64
168 /* Assume anything <= 4GB can be handled by IOMMU.
169 Actually some IOMMUs can handle everything, but I don't
170 know of a way to test this here. */
171 if (b_pfn < (min_t(u64, 0x100000000UL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
173 q->bounce_pfn = max_low_pfn;
175 if (b_pfn < blk_max_low_pfn)
177 q->bounce_pfn = b_pfn;
180 init_emergency_isa_pool();
181 q->bounce_gfp = GFP_NOIO | GFP_DMA;
182 q->bounce_pfn = b_pfn;
185 EXPORT_SYMBOL(blk_queue_bounce_limit);
188 * blk_queue_max_sectors - set max sectors for a request for this queue
189 * @q: the request queue for the device
190 * @max_sectors: max sectors in the usual 512b unit
193 * Enables a low level driver to set an upper limit on the size of
196 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
198 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
199 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
200 printk(KERN_INFO "%s: set to minimum %d\n",
201 __func__, max_sectors);
204 if (BLK_DEF_MAX_SECTORS > max_sectors)
205 q->max_hw_sectors = q->max_sectors = max_sectors;
207 q->max_sectors = BLK_DEF_MAX_SECTORS;
208 q->max_hw_sectors = max_sectors;
211 EXPORT_SYMBOL(blk_queue_max_sectors);
214 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
215 * @q: the request queue for the device
216 * @max_segments: max number of segments
219 * Enables a low level driver to set an upper limit on the number of
220 * physical data segments in a request. This would be the largest sized
221 * scatter list the driver could handle.
223 void blk_queue_max_phys_segments(struct request_queue *q,
224 unsigned short max_segments)
228 printk(KERN_INFO "%s: set to minimum %d\n",
229 __func__, max_segments);
232 q->max_phys_segments = max_segments;
234 EXPORT_SYMBOL(blk_queue_max_phys_segments);
237 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
238 * @q: the request queue for the device
239 * @max_segments: max number of segments
242 * Enables a low level driver to set an upper limit on the number of
243 * hw data segments in a request. This would be the largest number of
244 * address/length pairs the host adapter can actually give at once
247 void blk_queue_max_hw_segments(struct request_queue *q,
248 unsigned short max_segments)
252 printk(KERN_INFO "%s: set to minimum %d\n",
253 __func__, max_segments);
256 q->max_hw_segments = max_segments;
258 EXPORT_SYMBOL(blk_queue_max_hw_segments);
261 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
262 * @q: the request queue for the device
263 * @max_size: max size of segment in bytes
266 * Enables a low level driver to set an upper limit on the size of a
269 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
271 if (max_size < PAGE_CACHE_SIZE) {
272 max_size = PAGE_CACHE_SIZE;
273 printk(KERN_INFO "%s: set to minimum %d\n",
277 q->max_segment_size = max_size;
279 EXPORT_SYMBOL(blk_queue_max_segment_size);
282 * blk_queue_hardsect_size - set hardware sector size for the queue
283 * @q: the request queue for the device
284 * @size: the hardware sector size, in bytes
287 * This should typically be set to the lowest possible sector size
288 * that the hardware can operate on (possible without reverting to
289 * even internal read-modify-write operations). Usually the default
290 * of 512 covers most hardware.
292 void blk_queue_hardsect_size(struct request_queue *q, unsigned short size)
294 q->hardsect_size = size;
296 EXPORT_SYMBOL(blk_queue_hardsect_size);
299 * Returns the minimum that is _not_ zero, unless both are zero.
301 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
304 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
305 * @t: the stacking driver (top)
306 * @b: the underlying device (bottom)
308 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
310 /* zero is "infinity" */
311 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
312 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
314 t->max_phys_segments = min(t->max_phys_segments, b->max_phys_segments);
315 t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments);
316 t->max_segment_size = min(t->max_segment_size, b->max_segment_size);
317 t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
320 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
322 spin_lock_irqsave(t->queue_lock, flags);
323 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
324 spin_unlock_irqrestore(t->queue_lock, flags);
327 EXPORT_SYMBOL(blk_queue_stack_limits);
330 * blk_queue_dma_pad - set pad mask
331 * @q: the request queue for the device
336 * Appending pad buffer to a request modifies the last entry of a
337 * scatter list such that it includes the pad buffer.
339 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
341 q->dma_pad_mask = mask;
343 EXPORT_SYMBOL(blk_queue_dma_pad);
346 * blk_queue_update_dma_pad - update pad mask
347 * @q: the request queue for the device
350 * Update dma pad mask.
352 * Appending pad buffer to a request modifies the last entry of a
353 * scatter list such that it includes the pad buffer.
355 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
357 if (mask > q->dma_pad_mask)
358 q->dma_pad_mask = mask;
360 EXPORT_SYMBOL(blk_queue_update_dma_pad);
363 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
364 * @q: the request queue for the device
365 * @dma_drain_needed: fn which returns non-zero if drain is necessary
366 * @buf: physically contiguous buffer
367 * @size: size of the buffer in bytes
369 * Some devices have excess DMA problems and can't simply discard (or
370 * zero fill) the unwanted piece of the transfer. They have to have a
371 * real area of memory to transfer it into. The use case for this is
372 * ATAPI devices in DMA mode. If the packet command causes a transfer
373 * bigger than the transfer size some HBAs will lock up if there
374 * aren't DMA elements to contain the excess transfer. What this API
375 * does is adjust the queue so that the buf is always appended
376 * silently to the scatterlist.
378 * Note: This routine adjusts max_hw_segments to make room for
379 * appending the drain buffer. If you call
380 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
381 * calling this routine, you must set the limit to one fewer than your
382 * device can support otherwise there won't be room for the drain
385 int blk_queue_dma_drain(struct request_queue *q,
386 dma_drain_needed_fn *dma_drain_needed,
387 void *buf, unsigned int size)
389 if (q->max_hw_segments < 2 || q->max_phys_segments < 2)
391 /* make room for appending the drain */
392 --q->max_hw_segments;
393 --q->max_phys_segments;
394 q->dma_drain_needed = dma_drain_needed;
395 q->dma_drain_buffer = buf;
396 q->dma_drain_size = size;
400 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
403 * blk_queue_segment_boundary - set boundary rules for segment merging
404 * @q: the request queue for the device
405 * @mask: the memory boundary mask
407 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
409 if (mask < PAGE_CACHE_SIZE - 1) {
410 mask = PAGE_CACHE_SIZE - 1;
411 printk(KERN_INFO "%s: set to minimum %lx\n",
415 q->seg_boundary_mask = mask;
417 EXPORT_SYMBOL(blk_queue_segment_boundary);
420 * blk_queue_dma_alignment - set dma length and memory alignment
421 * @q: the request queue for the device
422 * @mask: alignment mask
425 * set required memory and length alignment for direct dma transactions.
426 * this is used when buiding direct io requests for the queue.
429 void blk_queue_dma_alignment(struct request_queue *q, int mask)
431 q->dma_alignment = mask;
433 EXPORT_SYMBOL(blk_queue_dma_alignment);
436 * blk_queue_update_dma_alignment - update dma length and memory alignment
437 * @q: the request queue for the device
438 * @mask: alignment mask
441 * update required memory and length alignment for direct dma transactions.
442 * If the requested alignment is larger than the current alignment, then
443 * the current queue alignment is updated to the new value, otherwise it
444 * is left alone. The design of this is to allow multiple objects
445 * (driver, device, transport etc) to set their respective
446 * alignments without having them interfere.
449 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
451 BUG_ON(mask > PAGE_SIZE);
453 if (mask > q->dma_alignment)
454 q->dma_alignment = mask;
456 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
458 static int __init blk_settings_init(void)
460 blk_max_low_pfn = max_low_pfn - 1;
461 blk_max_pfn = max_pfn - 1;
464 subsys_initcall(blk_settings_init);