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_merge_bvec - set a merge_bvec function for queue 37 * @q: queue 38 * @mbfn: merge_bvec_fn 39 * 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 49 * honored. 50 */ 51 void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn) 52 { 53 q->merge_bvec_fn = mbfn; 54 } 55 EXPORT_SYMBOL(blk_queue_merge_bvec); 56 57 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn) 58 { 59 q->softirq_done_fn = fn; 60 } 61 EXPORT_SYMBOL(blk_queue_softirq_done); 62 63 /** 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 67 * 68 * Description: 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(). 78 * 79 * Caveat: 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. 84 **/ 85 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) 86 { 87 /* 88 * set defaults 89 */ 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; 103 104 q->unplug_thresh = 4; /* hmm */ 105 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */ 106 if (q->unplug_delay == 0) 107 q->unplug_delay = 1; 108 109 INIT_WORK(&q->unplug_work, blk_unplug_work); 110 111 q->unplug_timer.function = blk_unplug_timeout; 112 q->unplug_timer.data = (unsigned long)q; 113 114 /* 115 * by default assume old behaviour and bounce for any highmem page 116 */ 117 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH); 118 } 119 EXPORT_SYMBOL(blk_queue_make_request); 120 121 /** 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 125 * 126 * Description: 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. 131 **/ 132 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr) 133 { 134 unsigned long b_pfn = dma_addr >> PAGE_SHIFT; 135 int dma = 0; 136 137 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)) 143 dma = 1; 144 q->bounce_pfn = max_low_pfn; 145 #else 146 if (b_pfn < blk_max_low_pfn) 147 dma = 1; 148 q->bounce_pfn = b_pfn; 149 #endif 150 if (dma) { 151 init_emergency_isa_pool(); 152 q->bounce_gfp = GFP_NOIO | GFP_DMA; 153 q->bounce_pfn = b_pfn; 154 } 155 } 156 EXPORT_SYMBOL(blk_queue_bounce_limit); 157 158 /** 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 162 * 163 * Description: 164 * Enables a low level driver to set an upper limit on the size of 165 * received requests. 166 **/ 167 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors) 168 { 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); 173 } 174 175 if (BLK_DEF_MAX_SECTORS > max_sectors) 176 q->max_hw_sectors = q->max_sectors = max_sectors; 177 else { 178 q->max_sectors = BLK_DEF_MAX_SECTORS; 179 q->max_hw_sectors = max_sectors; 180 } 181 } 182 EXPORT_SYMBOL(blk_queue_max_sectors); 183 184 /** 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 188 * 189 * Description: 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. 193 **/ 194 void blk_queue_max_phys_segments(struct request_queue *q, 195 unsigned short max_segments) 196 { 197 if (!max_segments) { 198 max_segments = 1; 199 printk(KERN_INFO "%s: set to minimum %d\n", 200 __func__, max_segments); 201 } 202 203 q->max_phys_segments = max_segments; 204 } 205 EXPORT_SYMBOL(blk_queue_max_phys_segments); 206 207 /** 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 211 * 212 * Description: 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 216 * to the device. 217 **/ 218 void blk_queue_max_hw_segments(struct request_queue *q, 219 unsigned short max_segments) 220 { 221 if (!max_segments) { 222 max_segments = 1; 223 printk(KERN_INFO "%s: set to minimum %d\n", 224 __func__, max_segments); 225 } 226 227 q->max_hw_segments = max_segments; 228 } 229 EXPORT_SYMBOL(blk_queue_max_hw_segments); 230 231 /** 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 235 * 236 * Description: 237 * Enables a low level driver to set an upper limit on the size of a 238 * coalesced segment 239 **/ 240 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) 241 { 242 if (max_size < PAGE_CACHE_SIZE) { 243 max_size = PAGE_CACHE_SIZE; 244 printk(KERN_INFO "%s: set to minimum %d\n", 245 __func__, max_size); 246 } 247 248 q->max_segment_size = max_size; 249 } 250 EXPORT_SYMBOL(blk_queue_max_segment_size); 251 252 /** 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 256 * 257 * Description: 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. 262 **/ 263 void blk_queue_hardsect_size(struct request_queue *q, unsigned short size) 264 { 265 q->hardsect_size = size; 266 } 267 EXPORT_SYMBOL(blk_queue_hardsect_size); 268 269 /* 270 * Returns the minimum that is _not_ zero, unless both are zero. 271 */ 272 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r)) 273 274 /** 275 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers 276 * @t: the stacking driver (top) 277 * @b: the underlying device (bottom) 278 **/ 279 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b) 280 { 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); 284 285 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); 289 if (!t->queue_lock) 290 WARN_ON_ONCE(1); 291 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) { 292 unsigned long 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); 296 } 297 } 298 EXPORT_SYMBOL(blk_queue_stack_limits); 299 300 /** 301 * blk_queue_dma_pad - set pad mask 302 * @q: the request queue for the device 303 * @mask: pad mask 304 * 305 * Set dma pad mask. 306 * 307 * Appending pad buffer to a request modifies the last entry of a 308 * scatter list such that it includes the pad buffer. 309 **/ 310 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask) 311 { 312 q->dma_pad_mask = mask; 313 } 314 EXPORT_SYMBOL(blk_queue_dma_pad); 315 316 /** 317 * blk_queue_update_dma_pad - update pad mask 318 * @q: the request queue for the device 319 * @mask: pad mask 320 * 321 * Update dma pad mask. 322 * 323 * Appending pad buffer to a request modifies the last entry of a 324 * scatter list such that it includes the pad buffer. 325 **/ 326 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask) 327 { 328 if (mask > q->dma_pad_mask) 329 q->dma_pad_mask = mask; 330 } 331 EXPORT_SYMBOL(blk_queue_update_dma_pad); 332 333 /** 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 339 * 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. 348 * 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 354 * buffer. 355 */ 356 int blk_queue_dma_drain(struct request_queue *q, 357 dma_drain_needed_fn *dma_drain_needed, 358 void *buf, unsigned int size) 359 { 360 if (q->max_hw_segments < 2 || q->max_phys_segments < 2) 361 return -EINVAL; 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; 368 369 return 0; 370 } 371 EXPORT_SYMBOL_GPL(blk_queue_dma_drain); 372 373 /** 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 377 **/ 378 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask) 379 { 380 if (mask < PAGE_CACHE_SIZE - 1) { 381 mask = PAGE_CACHE_SIZE - 1; 382 printk(KERN_INFO "%s: set to minimum %lx\n", 383 __func__, mask); 384 } 385 386 q->seg_boundary_mask = mask; 387 } 388 EXPORT_SYMBOL(blk_queue_segment_boundary); 389 390 /** 391 * blk_queue_dma_alignment - set dma length and memory alignment 392 * @q: the request queue for the device 393 * @mask: alignment mask 394 * 395 * description: 396 * set required memory and length aligment for direct dma transactions. 397 * this is used when buiding direct io requests for the queue. 398 * 399 **/ 400 void blk_queue_dma_alignment(struct request_queue *q, int mask) 401 { 402 q->dma_alignment = mask; 403 } 404 EXPORT_SYMBOL(blk_queue_dma_alignment); 405 406 /** 407 * blk_queue_update_dma_alignment - update dma length and memory alignment 408 * @q: the request queue for the device 409 * @mask: alignment mask 410 * 411 * description: 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. 418 * 419 **/ 420 void blk_queue_update_dma_alignment(struct request_queue *q, int mask) 421 { 422 BUG_ON(mask > PAGE_SIZE); 423 424 if (mask > q->dma_alignment) 425 q->dma_alignment = mask; 426 } 427 EXPORT_SYMBOL(blk_queue_update_dma_alignment); 428 429 static int __init blk_settings_init(void) 430 { 431 blk_max_low_pfn = max_low_pfn - 1; 432 blk_max_pfn = max_pfn - 1; 433 return 0; 434 } 435 subsys_initcall(blk_settings_init); 436