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_merge_bvec - set a merge_bvec function for queue
38 * @mbfn: merge_bvec_fn
40 * Usually queues have static limitations on the max sectors or segments that
41 * we can put in a request. Stacking drivers may have some settings that
42 * are dynamic, and thus we have to query the queue whether it is ok to
43 * add a new bio_vec to a bio at a given offset or not. If the block device
44 * has such limitations, it needs to register a merge_bvec_fn to control
45 * the size of bio's sent to it. Note that a block device *must* allow a
46 * single page to be added to an empty bio. The block device driver may want
47 * to use the bio_split() function to deal with these bio's. By default
48 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
51 void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
53 q->merge_bvec_fn = mbfn;
55 EXPORT_SYMBOL(blk_queue_merge_bvec);
57 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
59 q->softirq_done_fn = fn;
61 EXPORT_SYMBOL(blk_queue_softirq_done);
64 * blk_queue_make_request - define an alternate make_request function for a device
65 * @q: the request queue for the device to be affected
66 * @mfn: the alternate make_request function
69 * The normal way for &struct bios to be passed to a device
70 * driver is for them to be collected into requests on a request
71 * queue, and then to allow the device driver to select requests
72 * off that queue when it is ready. This works well for many block
73 * devices. However some block devices (typically virtual devices
74 * such as md or lvm) do not benefit from the processing on the
75 * request queue, and are served best by having the requests passed
76 * directly to them. This can be achieved by providing a function
77 * to blk_queue_make_request().
80 * The driver that does this *must* be able to deal appropriately
81 * with buffers in "highmemory". This can be accomplished by either calling
82 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
83 * blk_queue_bounce() to create a buffer in normal memory.
85 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
90 q->nr_requests = BLKDEV_MAX_RQ;
91 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
92 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
93 q->make_request_fn = mfn;
94 q->backing_dev_info.ra_pages =
95 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
96 q->backing_dev_info.state = 0;
97 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
98 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
99 blk_queue_hardsect_size(q, 512);
100 blk_queue_dma_alignment(q, 511);
101 blk_queue_congestion_threshold(q);
102 q->nr_batching = BLK_BATCH_REQ;
104 q->unplug_thresh = 4; /* hmm */
105 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
106 if (q->unplug_delay == 0)
109 INIT_WORK(&q->unplug_work, blk_unplug_work);
111 q->unplug_timer.function = blk_unplug_timeout;
112 q->unplug_timer.data = (unsigned long)q;
115 * by default assume old behaviour and bounce for any highmem page
117 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
119 EXPORT_SYMBOL(blk_queue_make_request);
122 * blk_queue_bounce_limit - set bounce buffer limit for queue
123 * @q: the request queue for the device
124 * @dma_addr: bus address limit
127 * Different hardware can have different requirements as to what pages
128 * it can do I/O directly to. A low level driver can call
129 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
130 * buffers for doing I/O to pages residing above @page.
132 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr)
134 unsigned long b_pfn = dma_addr >> PAGE_SHIFT;
137 q->bounce_gfp = GFP_NOIO;
138 #if BITS_PER_LONG == 64
139 /* Assume anything <= 4GB can be handled by IOMMU.
140 Actually some IOMMUs can handle everything, but I don't
141 know of a way to test this here. */
142 if (b_pfn < (min_t(u64, 0x100000000UL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
144 q->bounce_pfn = max_low_pfn;
146 if (b_pfn < blk_max_low_pfn)
148 q->bounce_pfn = b_pfn;
151 init_emergency_isa_pool();
152 q->bounce_gfp = GFP_NOIO | GFP_DMA;
153 q->bounce_pfn = b_pfn;
156 EXPORT_SYMBOL(blk_queue_bounce_limit);
159 * blk_queue_max_sectors - set max sectors for a request for this queue
160 * @q: the request queue for the device
161 * @max_sectors: max sectors in the usual 512b unit
164 * Enables a low level driver to set an upper limit on the size of
167 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
169 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
170 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
171 printk(KERN_INFO "%s: set to minimum %d\n",
172 __func__, max_sectors);
175 if (BLK_DEF_MAX_SECTORS > max_sectors)
176 q->max_hw_sectors = q->max_sectors = max_sectors;
178 q->max_sectors = BLK_DEF_MAX_SECTORS;
179 q->max_hw_sectors = max_sectors;
182 EXPORT_SYMBOL(blk_queue_max_sectors);
185 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
186 * @q: the request queue for the device
187 * @max_segments: max number of segments
190 * Enables a low level driver to set an upper limit on the number of
191 * physical data segments in a request. This would be the largest sized
192 * scatter list the driver could handle.
194 void blk_queue_max_phys_segments(struct request_queue *q,
195 unsigned short max_segments)
199 printk(KERN_INFO "%s: set to minimum %d\n",
200 __func__, max_segments);
203 q->max_phys_segments = max_segments;
205 EXPORT_SYMBOL(blk_queue_max_phys_segments);
208 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
209 * @q: the request queue for the device
210 * @max_segments: max number of segments
213 * Enables a low level driver to set an upper limit on the number of
214 * hw data segments in a request. This would be the largest number of
215 * address/length pairs the host adapter can actually give as once
218 void blk_queue_max_hw_segments(struct request_queue *q,
219 unsigned short max_segments)
223 printk(KERN_INFO "%s: set to minimum %d\n",
224 __func__, max_segments);
227 q->max_hw_segments = max_segments;
229 EXPORT_SYMBOL(blk_queue_max_hw_segments);
232 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
233 * @q: the request queue for the device
234 * @max_size: max size of segment in bytes
237 * Enables a low level driver to set an upper limit on the size of a
240 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
242 if (max_size < PAGE_CACHE_SIZE) {
243 max_size = PAGE_CACHE_SIZE;
244 printk(KERN_INFO "%s: set to minimum %d\n",
248 q->max_segment_size = max_size;
250 EXPORT_SYMBOL(blk_queue_max_segment_size);
253 * blk_queue_hardsect_size - set hardware sector size for the queue
254 * @q: the request queue for the device
255 * @size: the hardware sector size, in bytes
258 * This should typically be set to the lowest possible sector size
259 * that the hardware can operate on (possible without reverting to
260 * even internal read-modify-write operations). Usually the default
261 * of 512 covers most hardware.
263 void blk_queue_hardsect_size(struct request_queue *q, unsigned short size)
265 q->hardsect_size = size;
267 EXPORT_SYMBOL(blk_queue_hardsect_size);
270 * Returns the minimum that is _not_ zero, unless both are zero.
272 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
275 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
276 * @t: the stacking driver (top)
277 * @b: the underlying device (bottom)
279 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
281 /* zero is "infinity" */
282 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
283 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
285 t->max_phys_segments = min(t->max_phys_segments, b->max_phys_segments);
286 t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments);
287 t->max_segment_size = min(t->max_segment_size, b->max_segment_size);
288 t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
291 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
293 spin_lock_irqsave(t->queue_lock, flags);
294 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
295 spin_unlock_irqrestore(t->queue_lock, flags);
298 EXPORT_SYMBOL(blk_queue_stack_limits);
301 * blk_queue_dma_pad - set pad mask
302 * @q: the request queue for the device
307 * Appending pad buffer to a request modifies the last entry of a
308 * scatter list such that it includes the pad buffer.
310 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
312 q->dma_pad_mask = mask;
314 EXPORT_SYMBOL(blk_queue_dma_pad);
317 * blk_queue_update_dma_pad - update pad mask
318 * @q: the request queue for the device
321 * Update dma pad mask.
323 * Appending pad buffer to a request modifies the last entry of a
324 * scatter list such that it includes the pad buffer.
326 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
328 if (mask > q->dma_pad_mask)
329 q->dma_pad_mask = mask;
331 EXPORT_SYMBOL(blk_queue_update_dma_pad);
334 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
335 * @q: the request queue for the device
336 * @dma_drain_needed: fn which returns non-zero if drain is necessary
337 * @buf: physically contiguous buffer
338 * @size: size of the buffer in bytes
340 * Some devices have excess DMA problems and can't simply discard (or
341 * zero fill) the unwanted piece of the transfer. They have to have a
342 * real area of memory to transfer it into. The use case for this is
343 * ATAPI devices in DMA mode. If the packet command causes a transfer
344 * bigger than the transfer size some HBAs will lock up if there
345 * aren't DMA elements to contain the excess transfer. What this API
346 * does is adjust the queue so that the buf is always appended
347 * silently to the scatterlist.
349 * Note: This routine adjusts max_hw_segments to make room for
350 * appending the drain buffer. If you call
351 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
352 * calling this routine, you must set the limit to one fewer than your
353 * device can support otherwise there won't be room for the drain
356 int blk_queue_dma_drain(struct request_queue *q,
357 dma_drain_needed_fn *dma_drain_needed,
358 void *buf, unsigned int size)
360 if (q->max_hw_segments < 2 || q->max_phys_segments < 2)
362 /* make room for appending the drain */
363 --q->max_hw_segments;
364 --q->max_phys_segments;
365 q->dma_drain_needed = dma_drain_needed;
366 q->dma_drain_buffer = buf;
367 q->dma_drain_size = size;
371 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
374 * blk_queue_segment_boundary - set boundary rules for segment merging
375 * @q: the request queue for the device
376 * @mask: the memory boundary mask
378 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
380 if (mask < PAGE_CACHE_SIZE - 1) {
381 mask = PAGE_CACHE_SIZE - 1;
382 printk(KERN_INFO "%s: set to minimum %lx\n",
386 q->seg_boundary_mask = mask;
388 EXPORT_SYMBOL(blk_queue_segment_boundary);
391 * blk_queue_dma_alignment - set dma length and memory alignment
392 * @q: the request queue for the device
393 * @mask: alignment mask
396 * set required memory and length aligment for direct dma transactions.
397 * this is used when buiding direct io requests for the queue.
400 void blk_queue_dma_alignment(struct request_queue *q, int mask)
402 q->dma_alignment = mask;
404 EXPORT_SYMBOL(blk_queue_dma_alignment);
407 * blk_queue_update_dma_alignment - update dma length and memory alignment
408 * @q: the request queue for the device
409 * @mask: alignment mask
412 * update required memory and length aligment for direct dma transactions.
413 * If the requested alignment is larger than the current alignment, then
414 * the current queue alignment is updated to the new value, otherwise it
415 * is left alone. The design of this is to allow multiple objects
416 * (driver, device, transport etc) to set their respective
417 * alignments without having them interfere.
420 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
422 BUG_ON(mask > PAGE_SIZE);
424 if (mask > q->dma_alignment)
425 q->dma_alignment = mask;
427 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
429 static int __init blk_settings_init(void)
431 blk_max_low_pfn = max_low_pfn - 1;
432 blk_max_pfn = max_pfn - 1;
435 subsys_initcall(blk_settings_init);