diff options
Diffstat (limited to 'block/blk-settings.c')
| -rw-r--r-- | block/blk-settings.c | 402 |
1 files changed, 402 insertions, 0 deletions
diff --git a/block/blk-settings.c b/block/blk-settings.c new file mode 100644 index 0000000..4df09a1 --- /dev/null +++ b/block/blk-settings.c @@ -0,0 +1,402 @@ +/* + * 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, blk_max_pfn; +EXPORT_SYMBOL(blk_max_low_pfn); +EXPORT_SYMBOL(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 bounce_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 (bounce_pfn < (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) + dma = 1; + q->bounce_pfn = max_low_pfn; +#else + if (bounce_pfn < blk_max_low_pfn) + dma = 1; + q->bounce_pfn = bounce_pfn; +#endif + if (dma) { + init_emergency_isa_pool(); + q->bounce_gfp = GFP_NOIO | GFP_DMA; + q->bounce_pfn = bounce_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("%s: set to minimum %d\n", __FUNCTION__, 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("%s: set to minimum %d\n", __FUNCTION__, 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("%s: set to minimum %d\n", __FUNCTION__, 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("%s: set to minimum %d\n", __FUNCTION__, 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)) + clear_bit(QUEUE_FLAG_CLUSTER, &t->queue_flags); +} + +EXPORT_SYMBOL(blk_queue_stack_limits); + +/** + * blk_queue_dma_drain - Set up a drain buffer for excess dma. + * + * @q: the request queue for the device + * @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, 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_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("%s: set to minimum %lx\n", __FUNCTION__, 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); + +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); |
