/* * Functions related to setting various queue properties from drivers */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h> #include <linux/bio.h> #include <linux/blkdev.h> #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */ #include "blk.h" unsigned long blk_max_low_pfn; EXPORT_SYMBOL(blk_max_low_pfn); unsigned long blk_max_pfn; /** * blk_queue_prep_rq - set a prepare_request function for queue * @q: queue * @pfn: prepare_request function * * It's possible for a queue to register a prepare_request callback which * is invoked before the request is handed to the request_fn. The goal of * the function is to prepare a request for I/O, it can be used to build a * cdb from the request data for instance. * */ void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn) { q->prep_rq_fn = pfn; } EXPORT_SYMBOL(blk_queue_prep_rq); /** * blk_queue_merge_bvec - set a merge_bvec function for queue * @q: queue * @mbfn: merge_bvec_fn * * Usually queues have static limitations on the max sectors or segments that * we can put in a request. Stacking drivers may have some settings that * are dynamic, and thus we have to query the queue whether it is ok to * add a new bio_vec to a bio at a given offset or not. If the block device * has such limitations, it needs to register a merge_bvec_fn to control * the size of bio's sent to it. Note that a block device *must* allow a * single page to be added to an empty bio. The block device driver may want * to use the bio_split() function to deal with these bio's. By default * no merge_bvec_fn is defined for a queue, and only the fixed limits are * honored. */ void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn) { q->merge_bvec_fn = mbfn; } EXPORT_SYMBOL(blk_queue_merge_bvec); void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn) { q->softirq_done_fn = fn; } EXPORT_SYMBOL(blk_queue_softirq_done); /** * blk_queue_make_request - define an alternate make_request function for a device * @q: the request queue for the device to be affected * @mfn: the alternate make_request function * * Description: * The normal way for &struct bios to be passed to a device * driver is for them to be collected into requests on a request * queue, and then to allow the device driver to select requests * off that queue when it is ready. This works well for many block * devices. However some block devices (typically virtual devices * such as md or lvm) do not benefit from the processing on the * request queue, and are served best by having the requests passed * directly to them. This can be achieved by providing a function * to blk_queue_make_request(). * * Caveat: * The driver that does this *must* be able to deal appropriately * with buffers in "highmemory". This can be accomplished by either calling * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling * blk_queue_bounce() to create a buffer in normal memory. **/ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) { /* * set defaults */ q->nr_requests = BLKDEV_MAX_RQ; blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS); blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS); q->make_request_fn = mfn; q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; q->backing_dev_info.state = 0; q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY; blk_queue_max_sectors(q, SAFE_MAX_SECTORS); blk_queue_hardsect_size(q, 512); blk_queue_dma_alignment(q, 511); blk_queue_congestion_threshold(q); q->nr_batching = BLK_BATCH_REQ; q->unplug_thresh = 4; /* hmm */ q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */ if (q->unplug_delay == 0) q->unplug_delay = 1; INIT_WORK(&q->unplug_work, blk_unplug_work); q->unplug_timer.function = blk_unplug_timeout; q->unplug_timer.data = (unsigned long)q; /* * by default assume old behaviour and bounce for any highmem page */ blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH); } EXPORT_SYMBOL(blk_queue_make_request); /** * blk_queue_bounce_limit - set bounce buffer limit for queue * @q: the request queue for the device * @dma_addr: bus address limit * * Description: * Different hardware can have different requirements as to what pages * it can do I/O directly to. A low level driver can call * blk_queue_bounce_limit to have lower memory pages allocated as bounce * buffers for doing I/O to pages residing above @page. **/ void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr) { unsigned long b_pfn = dma_addr >> PAGE_SHIFT; int dma = 0; q->bounce_gfp = GFP_NOIO; #if BITS_PER_LONG == 64 /* Assume anything <= 4GB can be handled by IOMMU. Actually some IOMMUs can handle everything, but I don't know of a way to test this here. */ if (b_pfn < (min_t(u64, 0x100000000UL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) dma = 1; q->bounce_pfn = max_low_pfn; #else if (b_pfn < blk_max_low_pfn) dma = 1; q->bounce_pfn = b_pfn; #endif if (dma) { init_emergency_isa_pool(); q->bounce_gfp = GFP_NOIO | GFP_DMA; q->bounce_pfn = b_pfn; } } EXPORT_SYMBOL(blk_queue_bounce_limit); /** * blk_queue_max_sectors - set max sectors for a request for this queue * @q: the request queue for the device * @max_sectors: max sectors in the usual 512b unit * * Description: * Enables a low level driver to set an upper limit on the size of * received requests. **/ void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors) { if ((max_sectors << 9) < PAGE_CACHE_SIZE) { max_sectors = 1 << (PAGE_CACHE_SHIFT - 9); printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_sectors); } if (BLK_DEF_MAX_SECTORS > max_sectors) q->max_hw_sectors = q->max_sectors = max_sectors; else { q->max_sectors = BLK_DEF_MAX_SECTORS; q->max_hw_sectors = max_sectors; } } EXPORT_SYMBOL(blk_queue_max_sectors); /** * blk_queue_max_phys_segments - set max phys segments for a request for this queue * @q: the request queue for the device * @max_segments: max number of segments * * Description: * Enables a low level driver to set an upper limit on the number of * physical data segments in a request. This would be the largest sized * scatter list the driver could handle. **/ void blk_queue_max_phys_segments(struct request_queue *q, unsigned short max_segments) { if (!max_segments) { max_segments = 1; printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_segments); } q->max_phys_segments = max_segments; } EXPORT_SYMBOL(blk_queue_max_phys_segments); /** * blk_queue_max_hw_segments - set max hw segments for a request for this queue * @q: the request queue for the device * @max_segments: max number of segments * * Description: * Enables a low level driver to set an upper limit on the number of * hw data segments in a request. This would be the largest number of * address/length pairs the host adapter can actually give as once * to the device. **/ void blk_queue_max_hw_segments(struct request_queue *q, unsigned short max_segments) { if (!max_segments) { max_segments = 1; printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_segments); } q->max_hw_segments = max_segments; } EXPORT_SYMBOL(blk_queue_max_hw_segments); /** * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg * @q: the request queue for the device * @max_size: max size of segment in bytes * * Description: * Enables a low level driver to set an upper limit on the size of a * coalesced segment **/ void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) { if (max_size < PAGE_CACHE_SIZE) { max_size = PAGE_CACHE_SIZE; printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_size); } q->max_segment_size = max_size; } EXPORT_SYMBOL(blk_queue_max_segment_size); /** * blk_queue_hardsect_size - set hardware sector size for the queue * @q: the request queue for the device * @size: the hardware sector size, in bytes * * Description: * This should typically be set to the lowest possible sector size * that the hardware can operate on (possible without reverting to * even internal read-modify-write operations). Usually the default * of 512 covers most hardware. **/ void blk_queue_hardsect_size(struct request_queue *q, unsigned short size) { q->hardsect_size = size; } EXPORT_SYMBOL(blk_queue_hardsect_size); /* * Returns the minimum that is _not_ zero, unless both are zero. */ #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r)) /** * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers * @t: the stacking driver (top) * @b: the underlying device (bottom) **/ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b) { /* zero is "infinity" */ t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors); t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors); t->max_phys_segments = min(t->max_phys_segments, b->max_phys_segments); t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments); t->max_segment_size = min(t->max_segment_size, b->max_segment_size); t->hardsect_size = max(t->hardsect_size, b->hardsect_size); if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) queue_flag_clear(QUEUE_FLAG_CLUSTER, t); } EXPORT_SYMBOL(blk_queue_stack_limits); /** * blk_queue_dma_pad - set pad mask * @q: the request queue for the device * @mask: pad mask * * Set pad mask. Direct IO requests are padded to the mask specified. * * Appending pad buffer to a request modifies ->data_len such that it * includes the pad buffer. The original requested data length can be * obtained using blk_rq_raw_data_len(). **/ void blk_queue_dma_pad(struct request_queue *q, unsigned int mask) { q->dma_pad_mask = mask; } EXPORT_SYMBOL(blk_queue_dma_pad); /** * blk_queue_dma_drain - Set up a drain buffer for excess dma. * @q: the request queue for the device * @dma_drain_needed: fn which returns non-zero if drain is necessary * @buf: physically contiguous buffer * @size: size of the buffer in bytes * * Some devices have excess DMA problems and can't simply discard (or * zero fill) the unwanted piece of the transfer. They have to have a * real area of memory to transfer it into. The use case for this is * ATAPI devices in DMA mode. If the packet command causes a transfer * bigger than the transfer size some HBAs will lock up if there * aren't DMA elements to contain the excess transfer. What this API * does is adjust the queue so that the buf is always appended * silently to the scatterlist. * * Note: This routine adjusts max_hw_segments to make room for * appending the drain buffer. If you call * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after * calling this routine, you must set the limit to one fewer than your * device can support otherwise there won't be room for the drain * buffer. */ int blk_queue_dma_drain(struct request_queue *q, dma_drain_needed_fn *dma_drain_needed, void *buf, unsigned int size) { if (q->max_hw_segments < 2 || q->max_phys_segments < 2) return -EINVAL; /* make room for appending the drain */ --q->max_hw_segments; --q->max_phys_segments; q->dma_drain_needed = dma_drain_needed; q->dma_drain_buffer = buf; q->dma_drain_size = size; return 0; } EXPORT_SYMBOL_GPL(blk_queue_dma_drain); /** * blk_queue_segment_boundary - set boundary rules for segment merging * @q: the request queue for the device * @mask: the memory boundary mask **/ void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask) { if (mask < PAGE_CACHE_SIZE - 1) { mask = PAGE_CACHE_SIZE - 1; printk(KERN_INFO "%s: set to minimum %lx\n", __func__, mask); } q->seg_boundary_mask = mask; } EXPORT_SYMBOL(blk_queue_segment_boundary); /** * blk_queue_dma_alignment - set dma length and memory alignment * @q: the request queue for the device * @mask: alignment mask * * description: * set required memory and length aligment for direct dma transactions. * this is used when buiding direct io requests for the queue. * **/ void blk_queue_dma_alignment(struct request_queue *q, int mask) { q->dma_alignment = mask; } EXPORT_SYMBOL(blk_queue_dma_alignment); /** * blk_queue_update_dma_alignment - update dma length and memory alignment * @q: the request queue for the device * @mask: alignment mask * * description: * update required memory and length aligment for direct dma transactions. * If the requested alignment is larger than the current alignment, then * the current queue alignment is updated to the new value, otherwise it * is left alone. The design of this is to allow multiple objects * (driver, device, transport etc) to set their respective * alignments without having them interfere. * **/ void blk_queue_update_dma_alignment(struct request_queue *q, int mask) { BUG_ON(mask > PAGE_SIZE); if (mask > q->dma_alignment) q->dma_alignment = mask; } EXPORT_SYMBOL(blk_queue_update_dma_alignment); static int __init blk_settings_init(void) { blk_max_low_pfn = max_low_pfn - 1; blk_max_pfn = max_pfn - 1; return 0; } subsys_initcall(blk_settings_init);