[thirdparty/linux.git] / lib / scatterlist.c

/*
 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
 *
 * Scatterlist handling helpers.
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2. See the file COPYING for more details.
 */
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/scatterlist.h>
#include <linux/highmem.h>

/**
 * sg_next - return the next scatterlist entry in a list
 * @sg:		The current sg entry
 *
 * Description:
 *   Usually the next entry will be @sg@ + 1, but if this sg element is part
 *   of a chained scatterlist, it could jump to the start of a new
 *   scatterlist array.
 *
 **/
struct scatterlist *sg_next(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
	BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
	if (sg_is_last(sg))
		return NULL;

	sg++;
	if (unlikely(sg_is_chain(sg)))
		sg = sg_chain_ptr(sg);

	return sg;
}
EXPORT_SYMBOL(sg_next);

/**
 * sg_last - return the last scatterlist entry in a list
 * @sgl:	First entry in the scatterlist
 * @nents:	Number of entries in the scatterlist
 *
 * Description:
 *   Should only be used casually, it (currently) scans the entire list
 *   to get the last entry.
 *
 *   Note that the @sgl@ pointer passed in need not be the first one,
 *   the important bit is that @nents@ denotes the number of entries that
 *   exist from @sgl@.
 *
 **/
struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
{
#ifndef ARCH_HAS_SG_CHAIN
	struct scatterlist *ret = &sgl[nents - 1];
#else
	struct scatterlist *sg, *ret = NULL;
	unsigned int i;

	for_each_sg(sgl, sg, nents, i)
		ret = sg;

#endif
#ifdef CONFIG_DEBUG_SG
	BUG_ON(sgl[0].sg_magic != SG_MAGIC);
	BUG_ON(!sg_is_last(ret));
#endif
	return ret;
}
EXPORT_SYMBOL(sg_last);

/**
 * sg_init_table - Initialize SG table
 * @sgl:	   The SG table
 * @nents:	   Number of entries in table
 *
 * Notes:
 *   If this is part of a chained sg table, sg_mark_end() should be
 *   used only on the last table part.
 *
 **/
void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
	memset(sgl, 0, sizeof(*sgl) * nents);
#ifdef CONFIG_DEBUG_SG
	{
		unsigned int i;
		for (i = 0; i < nents; i++)
			sgl[i].sg_magic = SG_MAGIC;
	}
#endif
	sg_mark_end(&sgl[nents - 1]);
}
EXPORT_SYMBOL(sg_init_table);

/**
 * sg_init_one - Initialize a single entry sg list
 * @sg:		 SG entry
 * @buf:	 Virtual address for IO
 * @buflen:	 IO length
 *
 **/
void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
{
	sg_init_table(sg, 1);
	sg_set_buf(sg, buf, buflen);
}
EXPORT_SYMBOL(sg_init_one);

/*
 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
 * helpers.
 */
static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
{
	if (nents == SG_MAX_SINGLE_ALLOC)
		return (struct scatterlist *) __get_free_page(gfp_mask);
	else
		return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
}

static void sg_kfree(struct scatterlist *sg, unsigned int nents)
{
	if (nents == SG_MAX_SINGLE_ALLOC)
		free_page((unsigned long) sg);
	else
		kfree(sg);
}

/**
 * __sg_free_table - Free a previously mapped sg table
 * @table:	The sg table header to use
 * @max_ents:	The maximum number of entries per single scatterlist
 * @free_fn:	Free function
 *
 *  Description:
 *    Free an sg table previously allocated and setup with
 *    __sg_alloc_table().  The @max_ents value must be identical to
 *    that previously used with __sg_alloc_table().
 *
 **/
void __sg_free_table(struct sg_table *table, unsigned int max_ents,
		     sg_free_fn *free_fn)
{
	struct scatterlist *sgl, *next;

	if (unlikely(!table->sgl))
		return;

	sgl = table->sgl;
	while (table->orig_nents) {
		unsigned int alloc_size = table->orig_nents;
		unsigned int sg_size;

		/*
		 * If we have more than max_ents segments left,
		 * then assign 'next' to the sg table after the current one.
		 * sg_size is then one less than alloc size, since the last
		 * element is the chain pointer.
		 */
		if (alloc_size > max_ents) {
			next = sg_chain_ptr(&sgl[max_ents - 1]);
			alloc_size = max_ents;
			sg_size = alloc_size - 1;
		} else {
			sg_size = alloc_size;
			next = NULL;
		}

		table->orig_nents -= sg_size;
		free_fn(sgl, alloc_size);
		sgl = next;
	}

	table->sgl = NULL;
}
EXPORT_SYMBOL(__sg_free_table);

/**
 * sg_free_table - Free a previously allocated sg table
 * @table:	The mapped sg table header
 *
 **/
void sg_free_table(struct sg_table *table)
{
	__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
}
EXPORT_SYMBOL(sg_free_table);

/**
 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
 * @table:	The sg table header to use
 * @nents:	Number of entries in sg list
 * @max_ents:	The maximum number of entries the allocator returns per call
 * @gfp_mask:	GFP allocation mask
 * @alloc_fn:	Allocator to use
 *
 * Description:
 *   This function returns a @table @nents long. The allocator is
 *   defined to return scatterlist chunks of maximum size @max_ents.
 *   Thus if @nents is bigger than @max_ents, the scatterlists will be
 *   chained in units of @max_ents.
 *
 * Notes:
 *   If this function returns non-0 (eg failure), the caller must call
 *   __sg_free_table() to cleanup any leftover allocations.
 *
 **/
int __sg_alloc_table(struct sg_table *table, unsigned int nents,
		     unsigned int max_ents, gfp_t gfp_mask,
		     sg_alloc_fn *alloc_fn)
{
	struct scatterlist *sg, *prv;
	unsigned int left;

#ifndef ARCH_HAS_SG_CHAIN
	BUG_ON(nents > max_ents);
#endif

	memset(table, 0, sizeof(*table));

	left = nents;
	prv = NULL;
	do {
		unsigned int sg_size, alloc_size = left;

		if (alloc_size > max_ents) {
			alloc_size = max_ents;
			sg_size = alloc_size - 1;
		} else
			sg_size = alloc_size;

		left -= sg_size;

		sg = alloc_fn(alloc_size, gfp_mask);
		if (unlikely(!sg))
			return -ENOMEM;

		sg_init_table(sg, alloc_size);
		table->nents = table->orig_nents += sg_size;

		/*
		 * If this is the first mapping, assign the sg table header.
		 * If this is not the first mapping, chain previous part.
		 */
		if (prv)
			sg_chain(prv, max_ents, sg);
		else
			table->sgl = sg;

		/*
		 * If no more entries after this one, mark the end
		 */
		if (!left)
			sg_mark_end(&sg[sg_size - 1]);

		/*
		 * only really needed for mempool backed sg allocations (like
		 * SCSI), a possible improvement here would be to pass the
		 * table pointer into the allocator and let that clear these
		 * flags
		 */
		gfp_mask &= ~__GFP_WAIT;
		gfp_mask |= __GFP_HIGH;
		prv = sg;
	} while (left);

	return 0;
}
EXPORT_SYMBOL(__sg_alloc_table);

/**
 * sg_alloc_table - Allocate and initialize an sg table
 * @table:	The sg table header to use
 * @nents:	Number of entries in sg list
 * @gfp_mask:	GFP allocation mask
 *
 *  Description:
 *    Allocate and initialize an sg table. If @nents@ is larger than
 *    SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
 *
 **/
int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
{
	int ret;

	ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
			       gfp_mask, sg_kmalloc);
	if (unlikely(ret))
		__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);

	return ret;
}
EXPORT_SYMBOL(sg_alloc_table);

/**
 * sg_miter_start - start mapping iteration over a sg list
 * @miter: sg mapping iter to be started
 * @sgl: sg list to iterate over
 * @nents: number of sg entries
 *
 * Description:
 *   Starts mapping iterator @miter.
 *
 * Context:
 *   Don't care.
 */
void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
		    unsigned int nents, unsigned int flags)
{
	memset(miter, 0, sizeof(struct sg_mapping_iter));

	miter->__sg = sgl;
	miter->__nents = nents;
	miter->__offset = 0;
	WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
	miter->__flags = flags;
}
EXPORT_SYMBOL(sg_miter_start);

/**
 * sg_miter_next - proceed mapping iterator to the next mapping
 * @miter: sg mapping iter to proceed
 *
 * Description:
 *   Proceeds @miter@ to the next mapping.  @miter@ should have been
 *   started using sg_miter_start().  On successful return,
 *   @miter@->page, @miter@->addr and @miter@->length point to the
 *   current mapping.
 *
 * Context:
 *   IRQ disabled if SG_MITER_ATOMIC.  IRQ must stay disabled till
 *   @miter@ is stopped.  May sleep if !SG_MITER_ATOMIC.
 *
 * Returns:
 *   true if @miter contains the next mapping.  false if end of sg
 *   list is reached.
 */
bool sg_miter_next(struct sg_mapping_iter *miter)
{
	unsigned int off, len;

	/* check for end and drop resources from the last iteration */
	if (!miter->__nents)
		return false;

	sg_miter_stop(miter);

	/* get to the next sg if necessary.  __offset is adjusted by stop */
	while (miter->__offset == miter->__sg->length) {
		if (--miter->__nents) {
			miter->__sg = sg_next(miter->__sg);
			miter->__offset = 0;
		} else
			return false;
	}

	/* map the next page */
	off = miter->__sg->offset + miter->__offset;
	len = miter->__sg->length - miter->__offset;

	miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT);
	off &= ~PAGE_MASK;
	miter->length = min_t(unsigned int, len, PAGE_SIZE - off);
	miter->consumed = miter->length;

	if (miter->__flags & SG_MITER_ATOMIC)
		miter->addr = kmap_atomic(miter->page, KM_BIO_SRC_IRQ) + off;
	else
		miter->addr = kmap(miter->page) + off;

	return true;
}
EXPORT_SYMBOL(sg_miter_next);

/**
 * sg_miter_stop - stop mapping iteration
 * @miter: sg mapping iter to be stopped
 *
 * Description:
 *   Stops mapping iterator @miter.  @miter should have been started
 *   started using sg_miter_start().  A stopped iteration can be
 *   resumed by calling sg_miter_next() on it.  This is useful when
 *   resources (kmap) need to be released during iteration.
 *
 * Context:
 *   IRQ disabled if the SG_MITER_ATOMIC is set.  Don't care otherwise.
 */
void sg_miter_stop(struct sg_mapping_iter *miter)
{
	WARN_ON(miter->consumed > miter->length);

	/* drop resources from the last iteration */
	if (miter->addr) {
		miter->__offset += miter->consumed;

		if (miter->__flags & SG_MITER_TO_SG)
			flush_kernel_dcache_page(miter->page);

		if (miter->__flags & SG_MITER_ATOMIC) {
			WARN_ON(!irqs_disabled());
			kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ);
		} else
			kunmap(miter->page);

		miter->page = NULL;
		miter->addr = NULL;
		miter->length = 0;
		miter->consumed = 0;
	}
}
EXPORT_SYMBOL(sg_miter_stop);

/**
 * sg_copy_buffer - Copy data between a linear buffer and an SG list
 * @sgl:		 The SG list
 * @nents:		 Number of SG entries
 * @buf:		 Where to copy from
 * @buflen:		 The number of bytes to copy
 * @to_buffer: 		 transfer direction (non zero == from an sg list to a
 * 			 buffer, 0 == from a buffer to an sg list
 *
 * Returns the number of copied bytes.
 *
 **/
static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
			     void *buf, size_t buflen, int to_buffer)
{
	unsigned int offset = 0;
	struct sg_mapping_iter miter;
	unsigned long flags;
	unsigned int sg_flags = SG_MITER_ATOMIC;

	if (to_buffer)
		sg_flags |= SG_MITER_FROM_SG;
	else
		sg_flags |= SG_MITER_TO_SG;

	sg_miter_start(&miter, sgl, nents, sg_flags);

	local_irq_save(flags);

	while (sg_miter_next(&miter) && offset < buflen) {
		unsigned int len;

		len = min(miter.length, buflen - offset);

		if (to_buffer)
			memcpy(buf + offset, miter.addr, len);
		else
			memcpy(miter.addr, buf + offset, len);

		offset += len;
	}

	sg_miter_stop(&miter);

	local_irq_restore(flags);
	return offset;
}

/**
 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
 * @sgl:		 The SG list
 * @nents:		 Number of SG entries
 * @buf:		 Where to copy from
 * @buflen:		 The number of bytes to copy
 *
 * Returns the number of copied bytes.
 *
 **/
size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
			   void *buf, size_t buflen)
{
	return sg_copy_buffer(sgl, nents, buf, buflen, 0);
}
EXPORT_SYMBOL(sg_copy_from_buffer);

/**
 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
 * @sgl:		 The SG list
 * @nents:		 Number of SG entries
 * @buf:		 Where to copy to
 * @buflen:		 The number of bytes to copy
 *
 * Returns the number of copied bytes.
 *
 **/
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
			 void *buf, size_t buflen)
{
	return sg_copy_buffer(sgl, nents, buf, buflen, 1);
}
EXPORT_SYMBOL(sg_copy_to_buffer);
Commit	Line	Data
0db9299f JA	1	/*
	2	* Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
	3	*
	4	* Scatterlist handling helpers.
	5	*
	6	* This source code is licensed under the GNU General Public License,
	7	* Version 2. See the file COPYING for more details.
	8	*/
	9	#include <linux/module.h>
5a0e3ad6	10	#include <linux/slab.h>
0db9299f	11	#include <linux/scatterlist.h>
b1adaf65	12	#include <linux/highmem.h>
0db9299f JA	13
	14	/**
	15	* sg_next - return the next scatterlist entry in a list
	16	* @sg: The current sg entry
	17	*
	18	* Description:
	19	* Usually the next entry will be @sg@ + 1, but if this sg element is part
	20	* of a chained scatterlist, it could jump to the start of a new
	21	* scatterlist array.
	22	*
	23	**/
	24	struct scatterlist sg_next(struct scatterlist sg)
	25	{
	26	#ifdef CONFIG_DEBUG_SG
	27	BUG_ON(sg->sg_magic != SG_MAGIC);
	28	#endif
	29	if (sg_is_last(sg))
	30	return NULL;
	31
	32	sg++;
	33	if (unlikely(sg_is_chain(sg)))
	34	sg = sg_chain_ptr(sg);
	35
	36	return sg;
	37	}
	38	EXPORT_SYMBOL(sg_next);
	39
	40	/**
	41	* sg_last - return the last scatterlist entry in a list
	42	* @sgl: First entry in the scatterlist
	43	* @nents: Number of entries in the scatterlist
	44	*
	45	* Description:
	46	* Should only be used casually, it (currently) scans the entire list
	47	* to get the last entry.
	48	*
	49	* Note that the @sgl@ pointer passed in need not be the first one,
	50	* the important bit is that @nents@ denotes the number of entries that
	51	* exist from @sgl@.
	52	*
	53	**/
	54	struct scatterlist sg_last(struct scatterlist sgl, unsigned int nents)
	55	{
	56	#ifndef ARCH_HAS_SG_CHAIN
	57	struct scatterlist *ret = &sgl[nents - 1];
	58	#else
	59	struct scatterlist sg, ret = NULL;
	60	unsigned int i;
	61
	62	for_each_sg(sgl, sg, nents, i)
	63	ret = sg;
	64
	65	#endif
	66	#ifdef CONFIG_DEBUG_SG
	67	BUG_ON(sgl[0].sg_magic != SG_MAGIC);
	68	BUG_ON(!sg_is_last(ret));
	69	#endif
	70	return ret;
	71	}
	72	EXPORT_SYMBOL(sg_last);
	73
	74	/**
	75	* sg_init_table - Initialize SG table
	76	* @sgl: The SG table
77	* @nents: Number of entries in table
78	*
79	* Notes:
80	* If this is part of a chained sg table, sg_mark_end() should be
81	* used only on the last table part.
82	*
83	**/
84	void sg_init_table(struct scatterlist *sgl, unsigned int nents)
85	{
86	memset(sgl, 0, sizeof(sgl) nents);
87	#ifdef CONFIG_DEBUG_SG
88	{
89	unsigned int i;
90	for (i = 0; i < nents; i++)
91	sgl[i].sg_magic = SG_MAGIC;
92	}
93	#endif
94	sg_mark_end(&sgl[nents - 1]);
95	}
96	EXPORT_SYMBOL(sg_init_table);
97
98	/**
99	* sg_init_one - Initialize a single entry sg list
100	* @sg: SG entry
101	* @buf: Virtual address for IO
102	* @buflen: IO length
103	*
104	**/
105	void sg_init_one(struct scatterlist sg, const void buf, unsigned int buflen)
106	{
107	sg_init_table(sg, 1);
108	sg_set_buf(sg, buf, buflen);
109	}
110	EXPORT_SYMBOL(sg_init_one);
111
112	/*
113	* The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
114	* helpers.
115	*/
116	static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
117	{
118	if (nents == SG_MAX_SINGLE_ALLOC)
119	return (struct scatterlist *) __get_free_page(gfp_mask);
120	else
121	return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
122	}
123
124	static void sg_kfree(struct scatterlist *sg, unsigned int nents)
125	{
126	if (nents == SG_MAX_SINGLE_ALLOC)
127	free_page((unsigned long) sg);
128	else
129	kfree(sg);
130	}
131
132	/**
133	* __sg_free_table - Free a previously mapped sg table
134	* @table: The sg table header to use
7cedb1f1	135	* @max_ents: The maximum number of entries per single scatterlist
0db9299f JA	136	* @free_fn: Free function
	137	*
	138	* Description:
7cedb1f1 JB	139	* Free an sg table previously allocated and setup with
	140	* __sg_alloc_table(). The @max_ents value must be identical to
	141	* that previously used with __sg_alloc_table().
0db9299f JA	142	*
0db9299f JA	143	**/
7cedb1f1 JB	144	void __sg_free_table(struct sg_table *table, unsigned int max_ents,
7cedb1f1 JB	145	sg_free_fn *free_fn)
0db9299f JA	146	{
	147	struct scatterlist sgl, next;
	148
	149	if (unlikely(!table->sgl))
	150	return;
	151
	152	sgl = table->sgl;
	153	while (table->orig_nents) {
	154	unsigned int alloc_size = table->orig_nents;
	155	unsigned int sg_size;
	156
	157	/*
7cedb1f1	158	* If we have more than max_ents segments left,
0db9299f JA	159	* then assign 'next' to the sg table after the current one.
	160	* sg_size is then one less than alloc size, since the last
	161	* element is the chain pointer.
	162	*/
7cedb1f1 JB	163	if (alloc_size > max_ents) {
	164	next = sg_chain_ptr(&sgl[max_ents - 1]);
	165	alloc_size = max_ents;
0db9299f JA	166	sg_size = alloc_size - 1;
	167	} else {
	168	sg_size = alloc_size;
	169	next = NULL;
	170	}
	171
	172	table->orig_nents -= sg_size;
	173	free_fn(sgl, alloc_size);
	174	sgl = next;
	175	}
	176
	177	table->sgl = NULL;
	178	}
	179	EXPORT_SYMBOL(__sg_free_table);
	180
	181	/**
	182	* sg_free_table - Free a previously allocated sg table
	183	* @table: The mapped sg table header
	184	*
	185	**/
	186	void sg_free_table(struct sg_table *table)
	187	{
7cedb1f1	188	__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
0db9299f JA	189	}
	190	EXPORT_SYMBOL(sg_free_table);
	191
	192	/**
	193	* __sg_alloc_table - Allocate and initialize an sg table with given allocator
	194	* @table: The sg table header to use
	195	* @nents: Number of entries in sg list
7cedb1f1	196	* @max_ents: The maximum number of entries the allocator returns per call
0db9299f JA	197	* @gfp_mask: GFP allocation mask
	198	* @alloc_fn: Allocator to use
	199	*
7cedb1f1 JB	200	* Description:
	201	* This function returns a @table @nents long. The allocator is
	202	* defined to return scatterlist chunks of maximum size @max_ents.
	203	* Thus if @nents is bigger than @max_ents, the scatterlists will be
	204	* chained in units of @max_ents.
	205	*
0db9299f JA	206	* Notes:
	207	* If this function returns non-0 (eg failure), the caller must call
	208	* __sg_free_table() to cleanup any leftover allocations.
	209	*
	210	**/
7cedb1f1 JB	211	int __sg_alloc_table(struct sg_table *table, unsigned int nents,
7cedb1f1 JB	212	unsigned int max_ents, gfp_t gfp_mask,
0db9299f JA	213	sg_alloc_fn *alloc_fn)
	214	{
	215	struct scatterlist sg, prv;
	216	unsigned int left;
	217
	218	#ifndef ARCH_HAS_SG_CHAIN
7cedb1f1	219	BUG_ON(nents > max_ents);
0db9299f JA	220	#endif
	221
	222	memset(table, 0, sizeof(*table));
	223
	224	left = nents;
	225	prv = NULL;
	226	do {
	227	unsigned int sg_size, alloc_size = left;
	228
7cedb1f1 JB	229	if (alloc_size > max_ents) {
7cedb1f1 JB	230	alloc_size = max_ents;
0db9299f JA	231	sg_size = alloc_size - 1;
	232	} else
	233	sg_size = alloc_size;
	234
	235	left -= sg_size;
	236
	237	sg = alloc_fn(alloc_size, gfp_mask);
	238	if (unlikely(!sg))
	239	return -ENOMEM;
	240
	241	sg_init_table(sg, alloc_size);
	242	table->nents = table->orig_nents += sg_size;
	243
	244	/*
	245	* If this is the first mapping, assign the sg table header.
	246	* If this is not the first mapping, chain previous part.
	247	*/
	248	if (prv)
7cedb1f1	249	sg_chain(prv, max_ents, sg);
0db9299f JA	250	else
	251	table->sgl = sg;
	252
	253	/*
	254	* If no more entries after this one, mark the end
	255	*/
	256	if (!left)
	257	sg_mark_end(&sg[sg_size - 1]);
	258
	259	/*
	260	* only really needed for mempool backed sg allocations (like
	261	* SCSI), a possible improvement here would be to pass the
	262	* table pointer into the allocator and let that clear these
	263	* flags
	264	*/
	265	gfp_mask &= ~__GFP_WAIT;
	266	gfp_mask \|= __GFP_HIGH;
	267	prv = sg;
	268	} while (left);
	269
	270	return 0;
	271	}
	272	EXPORT_SYMBOL(__sg_alloc_table);
	273
	274	/**
	275	* sg_alloc_table - Allocate and initialize an sg table
	276	* @table: The sg table header to use
	277	* @nents: Number of entries in sg list
	278	* @gfp_mask: GFP allocation mask
	279	*
	280	* Description:
	281	* Allocate and initialize an sg table. If @nents@ is larger than
	282	* SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
	283	*
	284	**/
	285	int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
	286	{
	287	int ret;
	288
7cedb1f1 JB	289	ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
7cedb1f1 JB	290	gfp_mask, sg_kmalloc);
0db9299f	291	if (unlikely(ret))
7cedb1f1	292	__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
0db9299f JA	293
	294	return ret;
	295	}
	296	EXPORT_SYMBOL(sg_alloc_table);
b1adaf65	297
137d3edb TH	298	/**
	299	* sg_miter_start - start mapping iteration over a sg list
	300	* @miter: sg mapping iter to be started
	301	* @sgl: sg list to iterate over
	302	* @nents: number of sg entries
	303	*
	304	* Description:
	305	* Starts mapping iterator @miter.
	306	*
	307	* Context:
	308	* Don't care.
	309	*/
	310	void sg_miter_start(struct sg_mapping_iter miter, struct scatterlist sgl,
	311	unsigned int nents, unsigned int flags)
	312	{
	313	memset(miter, 0, sizeof(struct sg_mapping_iter));
	314
	315	miter->__sg = sgl;
	316	miter->__nents = nents;
	317	miter->__offset = 0;
6de7e356	318	WARN_ON(!(flags & (SG_MITER_TO_SG \| SG_MITER_FROM_SG)));
137d3edb TH	319	miter->__flags = flags;
	320	}
	321	EXPORT_SYMBOL(sg_miter_start);
	322
	323	/**
	324	* sg_miter_next - proceed mapping iterator to the next mapping
	325	* @miter: sg mapping iter to proceed
	326	*
	327	* Description:
	328	* Proceeds @miter@ to the next mapping. @miter@ should have been
	329	* started using sg_miter_start(). On successful return,
	330	* @miter@->page, @miter@->addr and @miter@->length point to the
	331	* current mapping.
	332	*
	333	* Context:
	334	* IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till
	335	* @miter@ is stopped. May sleep if !SG_MITER_ATOMIC.
	336	*
	337	* Returns:
	338	* true if @miter contains the next mapping. false if end of sg
	339	* list is reached.
	340	*/
	341	bool sg_miter_next(struct sg_mapping_iter *miter)
	342	{
	343	unsigned int off, len;
	344
	345	/* check for end and drop resources from the last iteration */
	346	if (!miter->__nents)
	347	return false;
	348
	349	sg_miter_stop(miter);
	350
	351	/* get to the next sg if necessary. __offset is adjusted by stop */
23c560a9 TH	352	while (miter->__offset == miter->__sg->length) {
	353	if (--miter->__nents) {
	354	miter->__sg = sg_next(miter->__sg);
	355	miter->__offset = 0;
	356	} else
	357	return false;
137d3edb TH	358	}
	359
	360	/* map the next page */
	361	off = miter->__sg->offset + miter->__offset;
	362	len = miter->__sg->length - miter->__offset;
	363
	364	miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT);
	365	off &= ~PAGE_MASK;
	366	miter->length = min_t(unsigned int, len, PAGE_SIZE - off);
	367	miter->consumed = miter->length;
	368
	369	if (miter->__flags & SG_MITER_ATOMIC)
	370	miter->addr = kmap_atomic(miter->page, KM_BIO_SRC_IRQ) + off;
	371	else
	372	miter->addr = kmap(miter->page) + off;
	373
	374	return true;
	375	}
	376	EXPORT_SYMBOL(sg_miter_next);
	377
	378	/**
	379	* sg_miter_stop - stop mapping iteration
	380	* @miter: sg mapping iter to be stopped
	381	*
	382	* Description:
	383	* Stops mapping iterator @miter. @miter should have been started
	384	* started using sg_miter_start(). A stopped iteration can be
	385	* resumed by calling sg_miter_next() on it. This is useful when
	386	* resources (kmap) need to be released during iteration.
	387	*
	388	* Context:
	389	* IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise.
	390	*/
	391	void sg_miter_stop(struct sg_mapping_iter *miter)
	392	{
	393	WARN_ON(miter->consumed > miter->length);
	394
	395	/* drop resources from the last iteration */
	396	if (miter->addr) {
	397	miter->__offset += miter->consumed;
	398
6de7e356 SAS	399	if (miter->__flags & SG_MITER_TO_SG)
	400	flush_kernel_dcache_page(miter->page);
	401
137d3edb TH	402	if (miter->__flags & SG_MITER_ATOMIC) {
	403	WARN_ON(!irqs_disabled());
	404	kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ);
	405	} else
f652c521	406	kunmap(miter->page);
137d3edb TH	407
	408	miter->page = NULL;
	409	miter->addr = NULL;
	410	miter->length = 0;
	411	miter->consumed = 0;
	412	}
	413	}
	414	EXPORT_SYMBOL(sg_miter_stop);
	415
b1adaf65 FT	416	/**
	417	* sg_copy_buffer - Copy data between a linear buffer and an SG list
	418	* @sgl: The SG list
	419	* @nents: Number of SG entries
	420	* @buf: Where to copy from
	421	* @buflen: The number of bytes to copy
	422	* @to_buffer: transfer direction (non zero == from an sg list to a
	423	* buffer, 0 == from a buffer to an sg list
	424	*
	425	* Returns the number of copied bytes.
	426	*
	427	**/
	428	static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
	429	void *buf, size_t buflen, int to_buffer)
	430	{
137d3edb TH	431	unsigned int offset = 0;
137d3edb TH	432	struct sg_mapping_iter miter;
50bed2e2	433	unsigned long flags;
6de7e356 SAS	434	unsigned int sg_flags = SG_MITER_ATOMIC;
	435
	436	if (to_buffer)
	437	sg_flags \|= SG_MITER_FROM_SG;
	438	else
	439	sg_flags \|= SG_MITER_TO_SG;
137d3edb	440
6de7e356	441	sg_miter_start(&miter, sgl, nents, sg_flags);
137d3edb	442
50bed2e2 FT	443	local_irq_save(flags);
50bed2e2 FT	444
137d3edb TH	445	while (sg_miter_next(&miter) && offset < buflen) {
	446	unsigned int len;
	447
	448	len = min(miter.length, buflen - offset);
	449
	450	if (to_buffer)
	451	memcpy(buf + offset, miter.addr, len);
6de7e356	452	else
137d3edb	453	memcpy(miter.addr, buf + offset, len);
b1adaf65	454
137d3edb	455	offset += len;
b1adaf65 FT	456	}
b1adaf65 FT	457
137d3edb TH	458	sg_miter_stop(&miter);
137d3edb TH	459
50bed2e2	460	local_irq_restore(flags);
137d3edb	461	return offset;
b1adaf65 FT	462	}
	463
	464	/**
	465	* sg_copy_from_buffer - Copy from a linear buffer to an SG list
	466	* @sgl: The SG list
	467	* @nents: Number of SG entries
	468	* @buf: Where to copy from
	469	* @buflen: The number of bytes to copy
	470	*
	471	* Returns the number of copied bytes.
	472	*
	473	**/
	474	size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
	475	void *buf, size_t buflen)
	476	{
	477	return sg_copy_buffer(sgl, nents, buf, buflen, 0);
	478	}
	479	EXPORT_SYMBOL(sg_copy_from_buffer);
	480
	481	/**
	482	* sg_copy_to_buffer - Copy from an SG list to a linear buffer
	483	* @sgl: The SG list
	484	* @nents: Number of SG entries
	485	* @buf: Where to copy to
	486	* @buflen: The number of bytes to copy
	487	*
	488	* Returns the number of copied bytes.
	489	*
	490	**/
	491	size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
	492	void *buf, size_t buflen)
	493	{
	494	return sg_copy_buffer(sgl, nents, buf, buflen, 1);
	495	}
	496	EXPORT_SYMBOL(sg_copy_to_buffer);