[mirror_ubuntu-artful-kernel.git] / block / blk-settings.c

/*
 * 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_set_discard - set a discard_sectors function for queue
 * @q:		queue
 * @dfn:	prepare_discard function
 *
 * It's possible for a queue to register a discard callback which is used
 * to transform a discard request into the appropriate type for the
 * hardware. If none is registered, then discard requests are failed
 * with %EOPNOTSUPP.
 *
 */
void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn)
{
	q->prepare_discard_fn = dfn;
}
EXPORT_SYMBOL(blk_queue_set_discard);

/**
 * 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 @dma_addr.
 **/
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 at 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 (!t->queue_lock)
		WARN_ON_ONCE(1);
	else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
		unsigned long flags;
		spin_lock_irqsave(t->queue_lock, flags);
		queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
		spin_unlock_irqrestore(t->queue_lock, flags);
	}
}
EXPORT_SYMBOL(blk_queue_stack_limits);

/**
 * blk_queue_dma_pad - set pad mask
 * @q:     the request queue for the device
 * @mask:  pad mask
 *
 * Set dma pad mask.
 *
 * Appending pad buffer to a request modifies the last entry of a
 * scatter list such that it includes the pad buffer.
 **/
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_update_dma_pad - update pad mask
 * @q:     the request queue for the device
 * @mask:  pad mask
 *
 * Update dma pad mask.
 *
 * Appending pad buffer to a request modifies the last entry of a
 * scatter list such that it includes the pad buffer.
 **/
void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
{
	if (mask > q->dma_pad_mask)
		q->dma_pad_mask = mask;
}
EXPORT_SYMBOL(blk_queue_update_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 alignment 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 alignment 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);
Commit	Line	Data
86db1e29 JA	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
6728cb0e	13	unsigned long blk_max_low_pfn;
86db1e29	14	EXPORT_SYMBOL(blk_max_low_pfn);
6728cb0e JA	15
6728cb0e JA	16	unsigned long blk_max_pfn;
86db1e29 JA	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	}
86db1e29 JA	33	EXPORT_SYMBOL(blk_queue_prep_rq);
86db1e29 JA	34
fb2dce86 DW	35	/**
	36	* blk_queue_set_discard - set a discard_sectors function for queue
	37	* @q: queue
	38	* @dfn: prepare_discard function
	39	*
	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
	43	* with %EOPNOTSUPP.
	44	*
	45	*/
	46	void blk_queue_set_discard(struct request_queue q, prepare_discard_fn dfn)
	47	{
	48	q->prepare_discard_fn = dfn;
	49	}
	50	EXPORT_SYMBOL(blk_queue_set_discard);
	51
86db1e29 JA	52	/**
	53	* blk_queue_merge_bvec - set a merge_bvec function for queue
	54	* @q: queue
	55	* @mbfn: merge_bvec_fn
	56	*
	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
	66	* honored.
	67	*/
	68	void blk_queue_merge_bvec(struct request_queue q, merge_bvec_fn mbfn)
	69	{
	70	q->merge_bvec_fn = mbfn;
	71	}
86db1e29 JA	72	EXPORT_SYMBOL(blk_queue_merge_bvec);
	73
	74	void blk_queue_softirq_done(struct request_queue q, softirq_done_fn fn)
	75	{
	76	q->softirq_done_fn = fn;
	77	}
86db1e29 JA	78	EXPORT_SYMBOL(blk_queue_softirq_done);
	79
	80	/**
	81	* blk_queue_make_request - define an alternate make_request function for a device
	82	* @q: the request queue for the device to be affected
	83	* @mfn: the alternate make_request function
	84	*
	85	* Description:
	86	* The normal way for &struct bios to be passed to a device
	87	* driver is for them to be collected into requests on a request
	88	* queue, and then to allow the device driver to select requests
	89	* off that queue when it is ready. This works well for many block
	90	* devices. However some block devices (typically virtual devices
	91	* such as md or lvm) do not benefit from the processing on the
	92	* request queue, and are served best by having the requests passed
	93	* directly to them. This can be achieved by providing a function
	94	* to blk_queue_make_request().
	95	*
	96	* Caveat:
	97	* The driver that does this must be able to deal appropriately
	98	* with buffers in "highmemory". This can be accomplished by either calling
	99	* __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
	100	* blk_queue_bounce() to create a buffer in normal memory.
	101	**/
6728cb0e	102	void blk_queue_make_request(struct request_queue q, make_request_fn mfn)
86db1e29 JA	103	{
	104	/*
	105	* set defaults
	106	*/
	107	q->nr_requests = BLKDEV_MAX_RQ;
	108	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
	109	blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
	110	q->make_request_fn = mfn;
6728cb0e JA	111	q->backing_dev_info.ra_pages =
6728cb0e JA	112	(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
86db1e29 JA	113	q->backing_dev_info.state = 0;
	114	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
	115	blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
	116	blk_queue_hardsect_size(q, 512);
	117	blk_queue_dma_alignment(q, 511);
	118	blk_queue_congestion_threshold(q);
	119	q->nr_batching = BLK_BATCH_REQ;
	120
	121	q->unplug_thresh = 4; /* hmm */
	122	q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
	123	if (q->unplug_delay == 0)
	124	q->unplug_delay = 1;
	125
	126	INIT_WORK(&q->unplug_work, blk_unplug_work);
	127
	128	q->unplug_timer.function = blk_unplug_timeout;
	129	q->unplug_timer.data = (unsigned long)q;
	130
	131	/*
	132	* by default assume old behaviour and bounce for any highmem page
	133	*/
	134	blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
	135	}
86db1e29 JA	136	EXPORT_SYMBOL(blk_queue_make_request);
	137
	138	/**
	139	* blk_queue_bounce_limit - set bounce buffer limit for queue
	140	* @q: the request queue for the device
	141	* @dma_addr: bus address limit
	142	*
	143	* Description:
	144	* Different hardware can have different requirements as to what pages
	145	* it can do I/O directly to. A low level driver can call
	146	* blk_queue_bounce_limit to have lower memory pages allocated as bounce
710027a4	147	* buffers for doing I/O to pages residing above @dma_addr.
86db1e29 JA	148	**/
	149	void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr)
	150	{
6728cb0e	151	unsigned long b_pfn = dma_addr >> PAGE_SHIFT;
86db1e29 JA	152	int dma = 0;
	153
	154	q->bounce_gfp = GFP_NOIO;
	155	#if BITS_PER_LONG == 64
	156	/* Assume anything <= 4GB can be handled by IOMMU.
	157	Actually some IOMMUs can handle everything, but I don't
	158	know of a way to test this here. */
00d61e3e	159	if (b_pfn < (min_t(u64, 0x100000000UL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
86db1e29 JA	160	dma = 1;
	161	q->bounce_pfn = max_low_pfn;
	162	#else
6728cb0e	163	if (b_pfn < blk_max_low_pfn)
86db1e29	164	dma = 1;
6728cb0e	165	q->bounce_pfn = b_pfn;
86db1e29 JA	166	#endif
	167	if (dma) {
	168	init_emergency_isa_pool();
	169	q->bounce_gfp = GFP_NOIO \| GFP_DMA;
6728cb0e	170	q->bounce_pfn = b_pfn;
86db1e29 JA	171	}
86db1e29 JA	172	}
86db1e29 JA	173	EXPORT_SYMBOL(blk_queue_bounce_limit);
	174
	175	/**
	176	* blk_queue_max_sectors - set max sectors for a request for this queue
	177	* @q: the request queue for the device
	178	* @max_sectors: max sectors in the usual 512b unit
	179	*
	180	* Description:
	181	* Enables a low level driver to set an upper limit on the size of
	182	* received requests.
	183	**/
	184	void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
	185	{
	186	if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
	187	max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
24c03d47 HH	188	printk(KERN_INFO "%s: set to minimum %d\n",
24c03d47 HH	189	__func__, max_sectors);
86db1e29 JA	190	}
	191
	192	if (BLK_DEF_MAX_SECTORS > max_sectors)
	193	q->max_hw_sectors = q->max_sectors = max_sectors;
	194	else {
	195	q->max_sectors = BLK_DEF_MAX_SECTORS;
	196	q->max_hw_sectors = max_sectors;
	197	}
	198	}
86db1e29 JA	199	EXPORT_SYMBOL(blk_queue_max_sectors);
	200
	201	/**
	202	* blk_queue_max_phys_segments - set max phys segments for a request for this queue
	203	* @q: the request queue for the device
	204	* @max_segments: max number of segments
	205	*
	206	* Description:
	207	* Enables a low level driver to set an upper limit on the number of
	208	* physical data segments in a request. This would be the largest sized
	209	* scatter list the driver could handle.
	210	**/
	211	void blk_queue_max_phys_segments(struct request_queue *q,
	212	unsigned short max_segments)
	213	{
	214	if (!max_segments) {
	215	max_segments = 1;
24c03d47 HH	216	printk(KERN_INFO "%s: set to minimum %d\n",
24c03d47 HH	217	__func__, max_segments);
86db1e29 JA	218	}
	219
	220	q->max_phys_segments = max_segments;
	221	}
86db1e29 JA	222	EXPORT_SYMBOL(blk_queue_max_phys_segments);
	223
	224	/**
	225	* blk_queue_max_hw_segments - set max hw segments for a request for this queue
	226	* @q: the request queue for the device
	227	* @max_segments: max number of segments
	228	*
	229	* Description:
	230	* Enables a low level driver to set an upper limit on the number of
	231	* hw data segments in a request. This would be the largest number of
710027a4	232	* address/length pairs the host adapter can actually give at once
86db1e29 JA	233	* to the device.
	234	**/
	235	void blk_queue_max_hw_segments(struct request_queue *q,
	236	unsigned short max_segments)
	237	{
	238	if (!max_segments) {
	239	max_segments = 1;
24c03d47 HH	240	printk(KERN_INFO "%s: set to minimum %d\n",
24c03d47 HH	241	__func__, max_segments);
86db1e29 JA	242	}
	243
	244	q->max_hw_segments = max_segments;
	245	}
86db1e29 JA	246	EXPORT_SYMBOL(blk_queue_max_hw_segments);
	247
	248	/**
	249	* blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
	250	* @q: the request queue for the device
	251	* @max_size: max size of segment in bytes
	252	*
	253	* Description:
	254	* Enables a low level driver to set an upper limit on the size of a
	255	* coalesced segment
	256	**/
	257	void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
	258	{
	259	if (max_size < PAGE_CACHE_SIZE) {
	260	max_size = PAGE_CACHE_SIZE;
24c03d47 HH	261	printk(KERN_INFO "%s: set to minimum %d\n",
24c03d47 HH	262	__func__, max_size);
86db1e29 JA	263	}
	264
	265	q->max_segment_size = max_size;
	266	}
86db1e29 JA	267	EXPORT_SYMBOL(blk_queue_max_segment_size);
	268
	269	/**
	270	* blk_queue_hardsect_size - set hardware sector size for the queue
	271	* @q: the request queue for the device
	272	* @size: the hardware sector size, in bytes
	273	*
	274	* Description:
	275	* This should typically be set to the lowest possible sector size
	276	* that the hardware can operate on (possible without reverting to
	277	* even internal read-modify-write operations). Usually the default
	278	* of 512 covers most hardware.
	279	**/
	280	void blk_queue_hardsect_size(struct request_queue *q, unsigned short size)
	281	{
	282	q->hardsect_size = size;
	283	}
86db1e29 JA	284	EXPORT_SYMBOL(blk_queue_hardsect_size);
	285
	286	/*
	287	* Returns the minimum that is _not_ zero, unless both are zero.
	288	*/
	289	#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
	290
	291	/**
	292	* blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
	293	* @t: the stacking driver (top)
	294	* @b: the underlying device (bottom)
	295	**/
	296	void blk_queue_stack_limits(struct request_queue t, struct request_queue b)
	297	{
	298	/* zero is "infinity" */
6728cb0e JA	299	t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
6728cb0e JA	300	t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
86db1e29	301
6728cb0e JA	302	t->max_phys_segments = min(t->max_phys_segments, b->max_phys_segments);
	303	t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments);
	304	t->max_segment_size = min(t->max_segment_size, b->max_segment_size);
	305	t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
e7e72bf6 NB	306	if (!t->queue_lock)
	307	WARN_ON_ONCE(1);
	308	else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
	309	unsigned long flags;
	310	spin_lock_irqsave(t->queue_lock, flags);
75ad23bc	311	queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
e7e72bf6 NB	312	spin_unlock_irqrestore(t->queue_lock, flags);
e7e72bf6 NB	313	}
86db1e29	314	}
86db1e29 JA	315	EXPORT_SYMBOL(blk_queue_stack_limits);
86db1e29 JA	316
e3790c7d TH	317	/**
	318	* blk_queue_dma_pad - set pad mask
	319	* @q: the request queue for the device
	320	* @mask: pad mask
	321	*
27f8221a	322	* Set dma pad mask.
e3790c7d	323	*
27f8221a FT	324	* Appending pad buffer to a request modifies the last entry of a
27f8221a FT	325	* scatter list such that it includes the pad buffer.
e3790c7d TH	326	**/
	327	void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
	328	{
	329	q->dma_pad_mask = mask;
	330	}
	331	EXPORT_SYMBOL(blk_queue_dma_pad);
	332
27f8221a FT	333	/**
	334	* blk_queue_update_dma_pad - update pad mask
	335	* @q: the request queue for the device
	336	* @mask: pad mask
	337	*
	338	* Update dma pad mask.
	339	*
	340	* Appending pad buffer to a request modifies the last entry of a
	341	* scatter list such that it includes the pad buffer.
	342	**/
	343	void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
	344	{
	345	if (mask > q->dma_pad_mask)
	346	q->dma_pad_mask = mask;
	347	}
	348	EXPORT_SYMBOL(blk_queue_update_dma_pad);
	349
86db1e29 JA	350	/**
86db1e29 JA	351	* blk_queue_dma_drain - Set up a drain buffer for excess dma.
86db1e29	352	* @q: the request queue for the device
2fb98e84	353	* @dma_drain_needed: fn which returns non-zero if drain is necessary
86db1e29 JA	354	* @buf: physically contiguous buffer
	355	* @size: size of the buffer in bytes
	356	*
	357	* Some devices have excess DMA problems and can't simply discard (or
	358	* zero fill) the unwanted piece of the transfer. They have to have a
	359	* real area of memory to transfer it into. The use case for this is
	360	* ATAPI devices in DMA mode. If the packet command causes a transfer
	361	* bigger than the transfer size some HBAs will lock up if there
	362	* aren't DMA elements to contain the excess transfer. What this API
	363	* does is adjust the queue so that the buf is always appended
	364	* silently to the scatterlist.
	365	*
	366	* Note: This routine adjusts max_hw_segments to make room for
	367	* appending the drain buffer. If you call
	368	* blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
	369	* calling this routine, you must set the limit to one fewer than your
	370	* device can support otherwise there won't be room for the drain
	371	* buffer.
	372	*/
448da4d2	373	int blk_queue_dma_drain(struct request_queue *q,
2fb98e84 TH	374	dma_drain_needed_fn *dma_drain_needed,
2fb98e84 TH	375	void *buf, unsigned int size)
86db1e29 JA	376	{
	377	if (q->max_hw_segments < 2 \|\| q->max_phys_segments < 2)
	378	return -EINVAL;
	379	/* make room for appending the drain */
	380	--q->max_hw_segments;
	381	--q->max_phys_segments;
2fb98e84	382	q->dma_drain_needed = dma_drain_needed;
86db1e29 JA	383	q->dma_drain_buffer = buf;
	384	q->dma_drain_size = size;
	385
	386	return 0;
	387	}
86db1e29 JA	388	EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
	389
	390	/**
	391	* blk_queue_segment_boundary - set boundary rules for segment merging
	392	* @q: the request queue for the device
	393	* @mask: the memory boundary mask
	394	**/
	395	void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
	396	{
	397	if (mask < PAGE_CACHE_SIZE - 1) {
	398	mask = PAGE_CACHE_SIZE - 1;
24c03d47 HH	399	printk(KERN_INFO "%s: set to minimum %lx\n",
24c03d47 HH	400	__func__, mask);
86db1e29 JA	401	}
	402
	403	q->seg_boundary_mask = mask;
	404	}
86db1e29 JA	405	EXPORT_SYMBOL(blk_queue_segment_boundary);
	406
	407	/**
	408	* blk_queue_dma_alignment - set dma length and memory alignment
	409	* @q: the request queue for the device
	410	* @mask: alignment mask
	411	*
	412	* description:
710027a4	413	* set required memory and length alignment for direct dma transactions.
86db1e29 JA	414	* this is used when buiding direct io requests for the queue.
	415	*
	416	**/
	417	void blk_queue_dma_alignment(struct request_queue *q, int mask)
	418	{
	419	q->dma_alignment = mask;
	420	}
86db1e29 JA	421	EXPORT_SYMBOL(blk_queue_dma_alignment);
	422
	423	/**
	424	* blk_queue_update_dma_alignment - update dma length and memory alignment
	425	* @q: the request queue for the device
	426	* @mask: alignment mask
	427	*
	428	* description:
710027a4	429	* update required memory and length alignment for direct dma transactions.
86db1e29 JA	430	* If the requested alignment is larger than the current alignment, then
	431	* the current queue alignment is updated to the new value, otherwise it
	432	* is left alone. The design of this is to allow multiple objects
	433	* (driver, device, transport etc) to set their respective
	434	* alignments without having them interfere.
	435	*
	436	**/
	437	void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
	438	{
	439	BUG_ON(mask > PAGE_SIZE);
	440
	441	if (mask > q->dma_alignment)
	442	q->dma_alignment = mask;
	443	}
86db1e29 JA	444	EXPORT_SYMBOL(blk_queue_update_dma_alignment);
86db1e29 JA	445
aeb3d3a8	446	static int __init blk_settings_init(void)
86db1e29 JA	447	{
	448	blk_max_low_pfn = max_low_pfn - 1;
	449	blk_max_pfn = max_pfn - 1;
	450	return 0;
	451	}
	452	subsys_initcall(blk_settings_init);