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![FUJITA Tomonori](/assets/img/avatar_default.png)
This patch adds new three helper functions to copy data between an SG list and a linear buffer. - sg_copy_from_buffer copies data from linear buffer to an SG list - sg_copy_to_buffer copies data from an SG list to a linear buffer When the APIs copy data from a linear buffer to an SG list, flush_kernel_dcache_page is called. It's not necessary for everyone but it's a no-op on most architectures and in general the API is not used in performance critical path. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Acked-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
396 lines
9.2 KiB
C
396 lines
9.2 KiB
C
/*
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* Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
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*
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* Scatterlist handling helpers.
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*
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* This source code is licensed under the GNU General Public License,
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* Version 2. See the file COPYING for more details.
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*/
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#include <linux/module.h>
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#include <linux/scatterlist.h>
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#include <linux/highmem.h>
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/**
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* sg_next - return the next scatterlist entry in a list
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* @sg: The current sg entry
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*
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* Description:
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* Usually the next entry will be @sg@ + 1, but if this sg element is part
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* of a chained scatterlist, it could jump to the start of a new
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* scatterlist array.
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*
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**/
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struct scatterlist *sg_next(struct scatterlist *sg)
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{
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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#endif
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if (sg_is_last(sg))
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return NULL;
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sg++;
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if (unlikely(sg_is_chain(sg)))
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sg = sg_chain_ptr(sg);
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return sg;
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}
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EXPORT_SYMBOL(sg_next);
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/**
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* sg_last - return the last scatterlist entry in a list
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* @sgl: First entry in the scatterlist
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* @nents: Number of entries in the scatterlist
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*
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* Description:
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* Should only be used casually, it (currently) scans the entire list
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* to get the last entry.
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*
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* Note that the @sgl@ pointer passed in need not be the first one,
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* the important bit is that @nents@ denotes the number of entries that
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* exist from @sgl@.
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*
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**/
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struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
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{
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#ifndef ARCH_HAS_SG_CHAIN
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struct scatterlist *ret = &sgl[nents - 1];
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#else
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struct scatterlist *sg, *ret = NULL;
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unsigned int i;
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for_each_sg(sgl, sg, nents, i)
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ret = sg;
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#endif
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sgl[0].sg_magic != SG_MAGIC);
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BUG_ON(!sg_is_last(ret));
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#endif
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return ret;
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}
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EXPORT_SYMBOL(sg_last);
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/**
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* sg_init_table - Initialize SG table
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* @sgl: The SG table
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* @nents: Number of entries in table
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*
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* Notes:
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* If this is part of a chained sg table, sg_mark_end() should be
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* used only on the last table part.
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*
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**/
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void sg_init_table(struct scatterlist *sgl, unsigned int nents)
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{
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memset(sgl, 0, sizeof(*sgl) * nents);
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#ifdef CONFIG_DEBUG_SG
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{
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unsigned int i;
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for (i = 0; i < nents; i++)
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sgl[i].sg_magic = SG_MAGIC;
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}
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#endif
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sg_mark_end(&sgl[nents - 1]);
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}
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EXPORT_SYMBOL(sg_init_table);
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/**
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* sg_init_one - Initialize a single entry sg list
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* @sg: SG entry
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* @buf: Virtual address for IO
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* @buflen: IO length
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*
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**/
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void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
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{
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sg_init_table(sg, 1);
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sg_set_buf(sg, buf, buflen);
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}
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EXPORT_SYMBOL(sg_init_one);
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/*
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* The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
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* helpers.
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*/
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static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
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{
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if (nents == SG_MAX_SINGLE_ALLOC)
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return (struct scatterlist *) __get_free_page(gfp_mask);
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else
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return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
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}
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static void sg_kfree(struct scatterlist *sg, unsigned int nents)
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{
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if (nents == SG_MAX_SINGLE_ALLOC)
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free_page((unsigned long) sg);
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else
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kfree(sg);
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}
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/**
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* __sg_free_table - Free a previously mapped sg table
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* @table: The sg table header to use
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* @max_ents: The maximum number of entries per single scatterlist
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* @free_fn: Free function
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*
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* Description:
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* Free an sg table previously allocated and setup with
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* __sg_alloc_table(). The @max_ents value must be identical to
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* that previously used with __sg_alloc_table().
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*
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**/
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void __sg_free_table(struct sg_table *table, unsigned int max_ents,
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sg_free_fn *free_fn)
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{
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struct scatterlist *sgl, *next;
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if (unlikely(!table->sgl))
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return;
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sgl = table->sgl;
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while (table->orig_nents) {
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unsigned int alloc_size = table->orig_nents;
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unsigned int sg_size;
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/*
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* If we have more than max_ents segments left,
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* then assign 'next' to the sg table after the current one.
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* sg_size is then one less than alloc size, since the last
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* element is the chain pointer.
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*/
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if (alloc_size > max_ents) {
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next = sg_chain_ptr(&sgl[max_ents - 1]);
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alloc_size = max_ents;
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sg_size = alloc_size - 1;
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} else {
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sg_size = alloc_size;
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next = NULL;
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}
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table->orig_nents -= sg_size;
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free_fn(sgl, alloc_size);
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sgl = next;
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}
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table->sgl = NULL;
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}
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EXPORT_SYMBOL(__sg_free_table);
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/**
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* sg_free_table - Free a previously allocated sg table
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* @table: The mapped sg table header
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*
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**/
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void sg_free_table(struct sg_table *table)
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{
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__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
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}
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EXPORT_SYMBOL(sg_free_table);
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/**
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* __sg_alloc_table - Allocate and initialize an sg table with given allocator
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* @table: The sg table header to use
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* @nents: Number of entries in sg list
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* @max_ents: The maximum number of entries the allocator returns per call
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* @gfp_mask: GFP allocation mask
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* @alloc_fn: Allocator to use
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*
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* Description:
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* This function returns a @table @nents long. The allocator is
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* defined to return scatterlist chunks of maximum size @max_ents.
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* Thus if @nents is bigger than @max_ents, the scatterlists will be
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* chained in units of @max_ents.
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*
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* Notes:
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* If this function returns non-0 (eg failure), the caller must call
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* __sg_free_table() to cleanup any leftover allocations.
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*
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**/
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int __sg_alloc_table(struct sg_table *table, unsigned int nents,
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unsigned int max_ents, gfp_t gfp_mask,
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sg_alloc_fn *alloc_fn)
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{
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struct scatterlist *sg, *prv;
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unsigned int left;
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#ifndef ARCH_HAS_SG_CHAIN
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BUG_ON(nents > max_ents);
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#endif
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memset(table, 0, sizeof(*table));
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left = nents;
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prv = NULL;
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do {
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unsigned int sg_size, alloc_size = left;
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if (alloc_size > max_ents) {
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alloc_size = max_ents;
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sg_size = alloc_size - 1;
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} else
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sg_size = alloc_size;
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left -= sg_size;
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sg = alloc_fn(alloc_size, gfp_mask);
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if (unlikely(!sg))
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return -ENOMEM;
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sg_init_table(sg, alloc_size);
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table->nents = table->orig_nents += sg_size;
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/*
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* If this is the first mapping, assign the sg table header.
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* If this is not the first mapping, chain previous part.
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*/
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if (prv)
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sg_chain(prv, max_ents, sg);
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else
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table->sgl = sg;
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/*
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* If no more entries after this one, mark the end
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*/
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if (!left)
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sg_mark_end(&sg[sg_size - 1]);
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/*
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* only really needed for mempool backed sg allocations (like
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* SCSI), a possible improvement here would be to pass the
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* table pointer into the allocator and let that clear these
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* flags
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*/
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gfp_mask &= ~__GFP_WAIT;
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gfp_mask |= __GFP_HIGH;
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prv = sg;
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} while (left);
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return 0;
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}
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EXPORT_SYMBOL(__sg_alloc_table);
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/**
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* sg_alloc_table - Allocate and initialize an sg table
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* @table: The sg table header to use
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* @nents: Number of entries in sg list
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* @gfp_mask: GFP allocation mask
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*
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* Description:
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* Allocate and initialize an sg table. If @nents@ is larger than
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* SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
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*
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**/
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int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
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{
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int ret;
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ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
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gfp_mask, sg_kmalloc);
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if (unlikely(ret))
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__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
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return ret;
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}
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EXPORT_SYMBOL(sg_alloc_table);
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/**
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* sg_copy_buffer - Copy data between a linear buffer and an SG list
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* @sgl: The SG list
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* @nents: Number of SG entries
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* @buf: Where to copy from
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* @buflen: The number of bytes to copy
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* @to_buffer: transfer direction (non zero == from an sg list to a
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* buffer, 0 == from a buffer to an sg list
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*
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* Returns the number of copied bytes.
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*
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**/
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static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen, int to_buffer)
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{
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struct scatterlist *sg;
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size_t buf_off = 0;
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int i;
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WARN_ON(!irqs_disabled());
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for_each_sg(sgl, sg, nents, i) {
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struct page *page;
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int n = 0;
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unsigned int sg_off = sg->offset;
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unsigned int sg_copy = sg->length;
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if (sg_copy > buflen)
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sg_copy = buflen;
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buflen -= sg_copy;
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while (sg_copy > 0) {
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unsigned int page_copy;
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void *p;
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page_copy = PAGE_SIZE - sg_off;
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if (page_copy > sg_copy)
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page_copy = sg_copy;
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page = nth_page(sg_page(sg), n);
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p = kmap_atomic(page, KM_BIO_SRC_IRQ);
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if (to_buffer)
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memcpy(buf + buf_off, p + sg_off, page_copy);
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else {
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memcpy(p + sg_off, buf + buf_off, page_copy);
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flush_kernel_dcache_page(page);
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}
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kunmap_atomic(p, KM_BIO_SRC_IRQ);
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buf_off += page_copy;
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sg_off += page_copy;
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if (sg_off == PAGE_SIZE) {
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sg_off = 0;
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n++;
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}
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sg_copy -= page_copy;
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}
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if (!buflen)
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break;
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}
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return buf_off;
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}
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/**
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* sg_copy_from_buffer - Copy from a linear buffer to an SG list
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* @sgl: The SG list
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* @nents: Number of SG entries
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* @buf: Where to copy from
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* @buflen: The number of bytes to copy
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*
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* Returns the number of copied bytes.
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*
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**/
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size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen)
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{
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return sg_copy_buffer(sgl, nents, buf, buflen, 0);
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}
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EXPORT_SYMBOL(sg_copy_from_buffer);
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/**
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* sg_copy_to_buffer - Copy from an SG list to a linear buffer
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* @sgl: The SG list
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* @nents: Number of SG entries
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* @buf: Where to copy to
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* @buflen: The number of bytes to copy
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*
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* Returns the number of copied bytes.
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*
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**/
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size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen)
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{
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return sg_copy_buffer(sgl, nents, buf, buflen, 1);
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}
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EXPORT_SYMBOL(sg_copy_to_buffer);
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