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