[linux.git] / lib / scatterlist.c

/*
 * Copyright (C) 2007 Jens Axboe <[email protected]>
 *
 * 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>
#include <linux/kmemleak.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) {
		/*
		 * Kmemleak doesn't track page allocations as they are not
		 * commonly used (in a raw form) for kernel data structures.
		 * As we chain together a list of pages and then a normal
		 * kmalloc (tracked by kmemleak), in order to for that last
		 * allocation not to become decoupled (and thus a
		 * false-positive) we need to inform kmemleak of all the
		 * intermediate allocations.
		 */
		void *ptr = (void *) __get_free_page(gfp_mask);
		kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
		return ptr;
	} 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) {
		kmemleak_free(sg);
		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)) {
			/*
			 * Adjust entry count to reflect that the last
			 * entry of the previous table won't be used for
			 * linkage.  Without this, sg_kfree() may get
			 * confused.
			 */
			if (prv)
				table->nents = ++table->orig_nents;

 			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 <[email protected]>
	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>
b94de9bb	13	#include <linux/kmemleak.h>
0db9299f JA	14
	15	/**
	16	* sg_next - return the next scatterlist entry in a list
	17	* @sg: The current sg entry
	18	*
	19	* Description:
	20	* Usually the next entry will be @sg@ + 1, but if this sg element is part
	21	* of a chained scatterlist, it could jump to the start of a new
	22	* scatterlist array.
	23	*
	24	**/
	25	struct scatterlist sg_next(struct scatterlist sg)
	26	{
	27	#ifdef CONFIG_DEBUG_SG
	28	BUG_ON(sg->sg_magic != SG_MAGIC);
	29	#endif
	30	if (sg_is_last(sg))
	31	return NULL;
	32
	33	sg++;
	34	if (unlikely(sg_is_chain(sg)))
	35	sg = sg_chain_ptr(sg);
	36
	37	return sg;
	38	}
	39	EXPORT_SYMBOL(sg_next);
	40
	41	/**
	42	* sg_last - return the last scatterlist entry in a list
	43	* @sgl: First entry in the scatterlist
	44	* @nents: Number of entries in the scatterlist
	45	*
	46	* Description:
	47	* Should only be used casually, it (currently) scans the entire list
	48	* to get the last entry.
	49	*
	50	* Note that the @sgl@ pointer passed in need not be the first one,
	51	* the important bit is that @nents@ denotes the number of entries that
	52	* exist from @sgl@.
	53	*
	54	**/
	55	struct scatterlist sg_last(struct scatterlist sgl, unsigned int nents)
	56	{
	57	#ifndef ARCH_HAS_SG_CHAIN
	58	struct scatterlist *ret = &sgl[nents - 1];
	59	#else
	60	struct scatterlist sg, ret = NULL;
	61	unsigned int i;
	62
	63	for_each_sg(sgl, sg, nents, i)
	64	ret = sg;
	65
	66	#endif
	67	#ifdef CONFIG_DEBUG_SG
	68	BUG_ON(sgl[0].sg_magic != SG_MAGIC);
	69	BUG_ON(!sg_is_last(ret));
	70	#endif
	71	return ret;
	72	}
	73	EXPORT_SYMBOL(sg_last);
	74
	75	/**
	76	* sg_init_table - Initialize SG table
	77	* @sgl: The SG table
78	* @nents: Number of entries in table
79	*
80	* Notes:
81	* If this is part of a chained sg table, sg_mark_end() should be
82	* used only on the last table part.
83	*
84	**/
85	void sg_init_table(struct scatterlist *sgl, unsigned int nents)
86	{
87	memset(sgl, 0, sizeof(sgl) nents);
88	#ifdef CONFIG_DEBUG_SG
89	{
90	unsigned int i;
91	for (i = 0; i < nents; i++)
92	sgl[i].sg_magic = SG_MAGIC;
93	}
94	#endif
95	sg_mark_end(&sgl[nents - 1]);
96	}
97	EXPORT_SYMBOL(sg_init_table);
98
99	/**
100	* sg_init_one - Initialize a single entry sg list
101	* @sg: SG entry
102	* @buf: Virtual address for IO
103	* @buflen: IO length
104	*
105	**/
106	void sg_init_one(struct scatterlist sg, const void buf, unsigned int buflen)
107	{
108	sg_init_table(sg, 1);
109	sg_set_buf(sg, buf, buflen);
110	}
111	EXPORT_SYMBOL(sg_init_one);
112
113	/*
114	* The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
115	* helpers.
116	*/
117	static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
118	{
b94de9bb CW	119	if (nents == SG_MAX_SINGLE_ALLOC) {
	120	/*
	121	* Kmemleak doesn't track page allocations as they are not
	122	* commonly used (in a raw form) for kernel data structures.
	123	* As we chain together a list of pages and then a normal
	124	* kmalloc (tracked by kmemleak), in order to for that last
	125	* allocation not to become decoupled (and thus a
	126	* false-positive) we need to inform kmemleak of all the
	127	* intermediate allocations.
	128	*/
	129	void ptr = (void ) __get_free_page(gfp_mask);
	130	kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
	131	return ptr;
	132	} else
0db9299f JA	133	return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
	134	}
	135
	136	static void sg_kfree(struct scatterlist *sg, unsigned int nents)
	137	{
b94de9bb CW	138	if (nents == SG_MAX_SINGLE_ALLOC) {
b94de9bb CW	139	kmemleak_free(sg);
0db9299f	140	free_page((unsigned long) sg);
b94de9bb	141	} else
0db9299f JA	142	kfree(sg);
	143	}
	144
	145	/**
	146	* __sg_free_table - Free a previously mapped sg table
	147	* @table: The sg table header to use
7cedb1f1	148	* @max_ents: The maximum number of entries per single scatterlist
0db9299f JA	149	* @free_fn: Free function
	150	*
	151	* Description:
7cedb1f1 JB	152	* Free an sg table previously allocated and setup with
	153	* __sg_alloc_table(). The @max_ents value must be identical to
	154	* that previously used with __sg_alloc_table().
0db9299f JA	155	*
0db9299f JA	156	**/
7cedb1f1 JB	157	void __sg_free_table(struct sg_table *table, unsigned int max_ents,
7cedb1f1 JB	158	sg_free_fn *free_fn)
0db9299f JA	159	{
	160	struct scatterlist sgl, next;
	161
	162	if (unlikely(!table->sgl))
	163	return;
	164
	165	sgl = table->sgl;
	166	while (table->orig_nents) {
	167	unsigned int alloc_size = table->orig_nents;
	168	unsigned int sg_size;
	169
	170	/*
7cedb1f1	171	* If we have more than max_ents segments left,
0db9299f JA	172	* then assign 'next' to the sg table after the current one.
	173	* sg_size is then one less than alloc size, since the last
	174	* element is the chain pointer.
	175	*/
7cedb1f1 JB	176	if (alloc_size > max_ents) {
	177	next = sg_chain_ptr(&sgl[max_ents - 1]);
	178	alloc_size = max_ents;
0db9299f JA	179	sg_size = alloc_size - 1;
	180	} else {
	181	sg_size = alloc_size;
	182	next = NULL;
	183	}
	184
	185	table->orig_nents -= sg_size;
	186	free_fn(sgl, alloc_size);
	187	sgl = next;
	188	}
	189
	190	table->sgl = NULL;
	191	}
	192	EXPORT_SYMBOL(__sg_free_table);
	193
	194	/**
	195	* sg_free_table - Free a previously allocated sg table
	196	* @table: The mapped sg table header
	197	*
	198	**/
	199	void sg_free_table(struct sg_table *table)
	200	{
7cedb1f1	201	__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
0db9299f JA	202	}
	203	EXPORT_SYMBOL(sg_free_table);
	204
	205	/**
	206	* __sg_alloc_table - Allocate and initialize an sg table with given allocator
	207	* @table: The sg table header to use
	208	* @nents: Number of entries in sg list
7cedb1f1	209	* @max_ents: The maximum number of entries the allocator returns per call
0db9299f JA	210	* @gfp_mask: GFP allocation mask
	211	* @alloc_fn: Allocator to use
	212	*
7cedb1f1 JB	213	* Description:
	214	* This function returns a @table @nents long. The allocator is
	215	* defined to return scatterlist chunks of maximum size @max_ents.
	216	* Thus if @nents is bigger than @max_ents, the scatterlists will be
	217	* chained in units of @max_ents.
	218	*
0db9299f JA	219	* Notes:
	220	* If this function returns non-0 (eg failure), the caller must call
	221	* __sg_free_table() to cleanup any leftover allocations.
	222	*
	223	**/
7cedb1f1 JB	224	int __sg_alloc_table(struct sg_table *table, unsigned int nents,
7cedb1f1 JB	225	unsigned int max_ents, gfp_t gfp_mask,
0db9299f JA	226	sg_alloc_fn *alloc_fn)
	227	{
	228	struct scatterlist sg, prv;
	229	unsigned int left;
	230
	231	#ifndef ARCH_HAS_SG_CHAIN
7cedb1f1	232	BUG_ON(nents > max_ents);
0db9299f JA	233	#endif
	234
	235	memset(table, 0, sizeof(*table));
	236
	237	left = nents;
	238	prv = NULL;
	239	do {
	240	unsigned int sg_size, alloc_size = left;
	241
7cedb1f1 JB	242	if (alloc_size > max_ents) {
7cedb1f1 JB	243	alloc_size = max_ents;
0db9299f JA	244	sg_size = alloc_size - 1;
	245	} else
	246	sg_size = alloc_size;
	247
	248	left -= sg_size;
	249
	250	sg = alloc_fn(alloc_size, gfp_mask);
edce6820 JC	251	if (unlikely(!sg)) {
	252	/*
	253	* Adjust entry count to reflect that the last
	254	* entry of the previous table won't be used for
	255	* linkage. Without this, sg_kfree() may get
	256	* confused.
	257	*/
	258	if (prv)
	259	table->nents = ++table->orig_nents;
	260
	261	return -ENOMEM;
	262	}
0db9299f JA	263
	264	sg_init_table(sg, alloc_size);
	265	table->nents = table->orig_nents += sg_size;
	266
	267	/*
	268	* If this is the first mapping, assign the sg table header.
	269	* If this is not the first mapping, chain previous part.
	270	*/
	271	if (prv)
7cedb1f1	272	sg_chain(prv, max_ents, sg);
0db9299f JA	273	else
	274	table->sgl = sg;
	275
	276	/*
	277	* If no more entries after this one, mark the end
	278	*/
	279	if (!left)
	280	sg_mark_end(&sg[sg_size - 1]);
	281
	282	/*
	283	* only really needed for mempool backed sg allocations (like
	284	* SCSI), a possible improvement here would be to pass the
	285	* table pointer into the allocator and let that clear these
	286	* flags
	287	*/
	288	gfp_mask &= ~__GFP_WAIT;
	289	gfp_mask \|= __GFP_HIGH;
	290	prv = sg;
	291	} while (left);
	292
	293	return 0;
	294	}
	295	EXPORT_SYMBOL(__sg_alloc_table);
	296
	297	/**
	298	* sg_alloc_table - Allocate and initialize an sg table
	299	* @table: The sg table header to use
	300	* @nents: Number of entries in sg list
	301	* @gfp_mask: GFP allocation mask
	302	*
	303	* Description:
	304	* Allocate and initialize an sg table. If @nents@ is larger than
	305	* SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
	306	*
	307	**/
	308	int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
	309	{
	310	int ret;
	311
7cedb1f1 JB	312	ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
7cedb1f1 JB	313	gfp_mask, sg_kmalloc);
0db9299f	314	if (unlikely(ret))
7cedb1f1	315	__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
0db9299f JA	316
	317	return ret;
	318	}
	319	EXPORT_SYMBOL(sg_alloc_table);
b1adaf65	320
137d3edb TH	321	/**
	322	* sg_miter_start - start mapping iteration over a sg list
	323	* @miter: sg mapping iter to be started
	324	* @sgl: sg list to iterate over
	325	* @nents: number of sg entries
	326	*
	327	* Description:
	328	* Starts mapping iterator @miter.
	329	*
	330	* Context:
	331	* Don't care.
	332	*/
	333	void sg_miter_start(struct sg_mapping_iter miter, struct scatterlist sgl,
	334	unsigned int nents, unsigned int flags)
	335	{
	336	memset(miter, 0, sizeof(struct sg_mapping_iter));
	337
	338	miter->__sg = sgl;
	339	miter->__nents = nents;
	340	miter->__offset = 0;
6de7e356	341	WARN_ON(!(flags & (SG_MITER_TO_SG \| SG_MITER_FROM_SG)));
137d3edb TH	342	miter->__flags = flags;
	343	}
	344	EXPORT_SYMBOL(sg_miter_start);
	345
	346	/**
	347	* sg_miter_next - proceed mapping iterator to the next mapping
	348	* @miter: sg mapping iter to proceed
	349	*
	350	* Description:
	351	* Proceeds @miter@ to the next mapping. @miter@ should have been
	352	* started using sg_miter_start(). On successful return,
	353	* @miter@->page, @miter@->addr and @miter@->length point to the
	354	* current mapping.
	355	*
	356	* Context:
	357	* IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till
	358	* @miter@ is stopped. May sleep if !SG_MITER_ATOMIC.
	359	*
	360	* Returns:
	361	* true if @miter contains the next mapping. false if end of sg
	362	* list is reached.
	363	*/
	364	bool sg_miter_next(struct sg_mapping_iter *miter)
	365	{
	366	unsigned int off, len;
	367
	368	/* check for end and drop resources from the last iteration */
	369	if (!miter->__nents)
	370	return false;
	371
	372	sg_miter_stop(miter);
	373
	374	/* get to the next sg if necessary. __offset is adjusted by stop */
23c560a9 TH	375	while (miter->__offset == miter->__sg->length) {
	376	if (--miter->__nents) {
	377	miter->__sg = sg_next(miter->__sg);
	378	miter->__offset = 0;
	379	} else
	380	return false;
137d3edb TH	381	}
	382
	383	/* map the next page */
	384	off = miter->__sg->offset + miter->__offset;
	385	len = miter->__sg->length - miter->__offset;
	386
	387	miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT);
	388	off &= ~PAGE_MASK;
	389	miter->length = min_t(unsigned int, len, PAGE_SIZE - off);
	390	miter->consumed = miter->length;
	391
	392	if (miter->__flags & SG_MITER_ATOMIC)
	393	miter->addr = kmap_atomic(miter->page, KM_BIO_SRC_IRQ) + off;
	394	else
	395	miter->addr = kmap(miter->page) + off;
	396
	397	return true;
	398	}
	399	EXPORT_SYMBOL(sg_miter_next);
	400
	401	/**
	402	* sg_miter_stop - stop mapping iteration
	403	* @miter: sg mapping iter to be stopped
	404	*
	405	* Description:
	406	* Stops mapping iterator @miter. @miter should have been started
	407	* started using sg_miter_start(). A stopped iteration can be
	408	* resumed by calling sg_miter_next() on it. This is useful when
	409	* resources (kmap) need to be released during iteration.
	410	*
	411	* Context:
	412	* IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise.
	413	*/
	414	void sg_miter_stop(struct sg_mapping_iter *miter)
	415	{
	416	WARN_ON(miter->consumed > miter->length);
	417
	418	/* drop resources from the last iteration */
	419	if (miter->addr) {
	420	miter->__offset += miter->consumed;
	421
6de7e356 SAS	422	if (miter->__flags & SG_MITER_TO_SG)
	423	flush_kernel_dcache_page(miter->page);
	424
137d3edb TH	425	if (miter->__flags & SG_MITER_ATOMIC) {
	426	WARN_ON(!irqs_disabled());
	427	kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ);
	428	} else
f652c521	429	kunmap(miter->page);
137d3edb TH	430
	431	miter->page = NULL;
	432	miter->addr = NULL;
	433	miter->length = 0;
	434	miter->consumed = 0;
	435	}
	436	}
	437	EXPORT_SYMBOL(sg_miter_stop);
	438
b1adaf65 FT	439	/**
	440	* sg_copy_buffer - Copy data between a linear buffer and an SG list
	441	* @sgl: The SG list
	442	* @nents: Number of SG entries
	443	* @buf: Where to copy from
	444	* @buflen: The number of bytes to copy
	445	* @to_buffer: transfer direction (non zero == from an sg list to a
	446	* buffer, 0 == from a buffer to an sg list
	447	*
	448	* Returns the number of copied bytes.
	449	*
	450	**/
	451	static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
	452	void *buf, size_t buflen, int to_buffer)
	453	{
137d3edb TH	454	unsigned int offset = 0;
137d3edb TH	455	struct sg_mapping_iter miter;
50bed2e2	456	unsigned long flags;
6de7e356 SAS	457	unsigned int sg_flags = SG_MITER_ATOMIC;
	458
	459	if (to_buffer)
	460	sg_flags \|= SG_MITER_FROM_SG;
	461	else
	462	sg_flags \|= SG_MITER_TO_SG;
137d3edb	463
6de7e356	464	sg_miter_start(&miter, sgl, nents, sg_flags);
137d3edb	465
50bed2e2 FT	466	local_irq_save(flags);
50bed2e2 FT	467
137d3edb TH	468	while (sg_miter_next(&miter) && offset < buflen) {
	469	unsigned int len;
	470
	471	len = min(miter.length, buflen - offset);
	472
	473	if (to_buffer)
	474	memcpy(buf + offset, miter.addr, len);
6de7e356	475	else
137d3edb	476	memcpy(miter.addr, buf + offset, len);
b1adaf65	477
137d3edb	478	offset += len;
b1adaf65 FT	479	}
b1adaf65 FT	480
137d3edb TH	481	sg_miter_stop(&miter);
137d3edb TH	482
50bed2e2	483	local_irq_restore(flags);
137d3edb	484	return offset;
b1adaf65 FT	485	}
	486
	487	/**
	488	* sg_copy_from_buffer - Copy from a linear buffer to an SG list
	489	* @sgl: The SG list
	490	* @nents: Number of SG entries
	491	* @buf: Where to copy from
	492	* @buflen: The number of bytes to copy
	493	*
	494	* Returns the number of copied bytes.
	495	*
	496	**/
	497	size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
	498	void *buf, size_t buflen)
	499	{
	500	return sg_copy_buffer(sgl, nents, buf, buflen, 0);
	501	}
	502	EXPORT_SYMBOL(sg_copy_from_buffer);
	503
	504	/**
	505	* sg_copy_to_buffer - Copy from an SG list to a linear buffer
	506	* @sgl: The SG list
	507	* @nents: Number of SG entries
	508	* @buf: Where to copy to
	509	* @buflen: The number of bytes to copy
	510	*
	511	* Returns the number of copied bytes.
	512	*
	513	**/
	514	size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
	515	void *buf, size_t buflen)
	516	{
	517	return sg_copy_buffer(sgl, nents, buf, buflen, 1);
	518	}
	519	EXPORT_SYMBOL(sg_copy_to_buffer);