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
->limits
.bounce_pfn
= max_low_pfn
;
184 if (b_pfn
< blk_max_low_pfn
)
186 q
->limits
.bounce_pfn
= b_pfn
;
189 init_emergency_isa_pool();
190 q
->bounce_gfp
= GFP_NOIO
| GFP_DMA
;
191 q
->limits
.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
->limits
.max_hw_sectors
= q
->limits
.max_sectors
= max_sectors
;
216 q
->limits
.max_sectors
= BLK_DEF_MAX_SECTORS
;
217 q
->limits
.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
->limits
.max_hw_sectors
= BLK_DEF_MAX_SECTORS
;
227 q
->limits
.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
->limits
.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
->limits
.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
->limits
.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
->limits
.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
->limits
.max_sectors
= min_not_zero(queue_max_sectors(t
),
329 queue_max_sectors(b
));
331 t
->limits
.max_hw_sectors
= min_not_zero(queue_max_hw_sectors(t
),
332 queue_max_hw_sectors(b
));
334 t
->limits
.seg_boundary_mask
= min_not_zero(queue_segment_boundary(t
),
335 queue_segment_boundary(b
));
337 t
->limits
.max_phys_segments
= min_not_zero(queue_max_phys_segments(t
),
338 queue_max_phys_segments(b
));
340 t
->limits
.max_hw_segments
= min_not_zero(queue_max_hw_segments(t
),
341 queue_max_hw_segments(b
));
343 t
->limits
.max_segment_size
= min_not_zero(queue_max_segment_size(t
),
344 queue_max_segment_size(b
));
346 t
->limits
.logical_block_size
= max(queue_logical_block_size(t
),
347 queue_logical_block_size(b
));
351 else if (!test_bit(QUEUE_FLAG_CLUSTER
, &b
->queue_flags
)) {
353 spin_lock_irqsave(t
->queue_lock
, flags
);
354 queue_flag_clear(QUEUE_FLAG_CLUSTER
, t
);
355 spin_unlock_irqrestore(t
->queue_lock
, flags
);
358 EXPORT_SYMBOL(blk_queue_stack_limits
);
361 * blk_queue_dma_pad - set pad mask
362 * @q: the request queue for the device
367 * Appending pad buffer to a request modifies the last entry of a
368 * scatter list such that it includes the pad buffer.
370 void blk_queue_dma_pad(struct request_queue
*q
, unsigned int mask
)
372 q
->dma_pad_mask
= mask
;
374 EXPORT_SYMBOL(blk_queue_dma_pad
);
377 * blk_queue_update_dma_pad - update pad mask
378 * @q: the request queue for the device
381 * Update dma pad mask.
383 * Appending pad buffer to a request modifies the last entry of a
384 * scatter list such that it includes the pad buffer.
386 void blk_queue_update_dma_pad(struct request_queue
*q
, unsigned int mask
)
388 if (mask
> q
->dma_pad_mask
)
389 q
->dma_pad_mask
= mask
;
391 EXPORT_SYMBOL(blk_queue_update_dma_pad
);
394 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
395 * @q: the request queue for the device
396 * @dma_drain_needed: fn which returns non-zero if drain is necessary
397 * @buf: physically contiguous buffer
398 * @size: size of the buffer in bytes
400 * Some devices have excess DMA problems and can't simply discard (or
401 * zero fill) the unwanted piece of the transfer. They have to have a
402 * real area of memory to transfer it into. The use case for this is
403 * ATAPI devices in DMA mode. If the packet command causes a transfer
404 * bigger than the transfer size some HBAs will lock up if there
405 * aren't DMA elements to contain the excess transfer. What this API
406 * does is adjust the queue so that the buf is always appended
407 * silently to the scatterlist.
409 * Note: This routine adjusts max_hw_segments to make room for
410 * appending the drain buffer. If you call
411 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
412 * calling this routine, you must set the limit to one fewer than your
413 * device can support otherwise there won't be room for the drain
416 int blk_queue_dma_drain(struct request_queue
*q
,
417 dma_drain_needed_fn
*dma_drain_needed
,
418 void *buf
, unsigned int size
)
420 if (queue_max_hw_segments(q
) < 2 || queue_max_phys_segments(q
) < 2)
422 /* make room for appending the drain */
423 blk_queue_max_hw_segments(q
, queue_max_hw_segments(q
) - 1);
424 blk_queue_max_phys_segments(q
, queue_max_phys_segments(q
) - 1);
425 q
->dma_drain_needed
= dma_drain_needed
;
426 q
->dma_drain_buffer
= buf
;
427 q
->dma_drain_size
= size
;
431 EXPORT_SYMBOL_GPL(blk_queue_dma_drain
);
434 * blk_queue_segment_boundary - set boundary rules for segment merging
435 * @q: the request queue for the device
436 * @mask: the memory boundary mask
438 void blk_queue_segment_boundary(struct request_queue
*q
, unsigned long mask
)
440 if (mask
< PAGE_CACHE_SIZE
- 1) {
441 mask
= PAGE_CACHE_SIZE
- 1;
442 printk(KERN_INFO
"%s: set to minimum %lx\n",
446 q
->limits
.seg_boundary_mask
= mask
;
448 EXPORT_SYMBOL(blk_queue_segment_boundary
);
451 * blk_queue_dma_alignment - set dma length and memory alignment
452 * @q: the request queue for the device
453 * @mask: alignment mask
456 * set required memory and length alignment for direct dma transactions.
457 * this is used when building direct io requests for the queue.
460 void blk_queue_dma_alignment(struct request_queue
*q
, int mask
)
462 q
->dma_alignment
= mask
;
464 EXPORT_SYMBOL(blk_queue_dma_alignment
);
467 * blk_queue_update_dma_alignment - update dma length and memory alignment
468 * @q: the request queue for the device
469 * @mask: alignment mask
472 * update required memory and length alignment for direct dma transactions.
473 * If the requested alignment is larger than the current alignment, then
474 * the current queue alignment is updated to the new value, otherwise it
475 * is left alone. The design of this is to allow multiple objects
476 * (driver, device, transport etc) to set their respective
477 * alignments without having them interfere.
480 void blk_queue_update_dma_alignment(struct request_queue
*q
, int mask
)
482 BUG_ON(mask
> PAGE_SIZE
);
484 if (mask
> q
->dma_alignment
)
485 q
->dma_alignment
= mask
;
487 EXPORT_SYMBOL(blk_queue_update_dma_alignment
);
489 static int __init
blk_settings_init(void)
491 blk_max_low_pfn
= max_low_pfn
- 1;
492 blk_max_pfn
= max_pfn
- 1;
495 subsys_initcall(blk_settings_init
);