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![Imre Deak](/assets/img/avatar_default.png)
For better code reuse use the newly added page iterator to iterate through the pages. The offset, length within the page is still calculated by the mapping iterator as well as the actual mapping. Idea from Tejun Heo. Signed-off-by: Imre Deak <imre.deak@intel.com> Cc: Maxim Levitsky <maximlevitsky@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: James Hogan <james.hogan@imgtec.com> Cc: Stephen Warren <swarren@wwwdotorg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
631 lines
16 KiB
C
631 lines
16 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/export.h>
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#include <linux/slab.h>
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#include <linux/scatterlist.h>
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#include <linux/highmem.h>
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#include <linux/kmemleak.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_nents - return total count of entries in scatterlist
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* @sg: The scatterlist
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*
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* Description:
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* Allows to know how many entries are in sg, taking into acount
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* chaining as well
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*
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**/
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int sg_nents(struct scatterlist *sg)
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{
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int nents;
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for (nents = 0; sg; sg = sg_next(sg))
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nents++;
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return nents;
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}
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EXPORT_SYMBOL(sg_nents);
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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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/*
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* Kmemleak doesn't track page allocations as they are not
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* commonly used (in a raw form) for kernel data structures.
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* As we chain together a list of pages and then a normal
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* kmalloc (tracked by kmemleak), in order to for that last
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* allocation not to become decoupled (and thus a
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* false-positive) we need to inform kmemleak of all the
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* intermediate allocations.
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*/
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void *ptr = (void *) __get_free_page(gfp_mask);
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kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
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return ptr;
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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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kmemleak_free(sg);
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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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if (WARN_ON_ONCE(nents > max_ents))
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return -EINVAL;
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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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/*
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* Adjust entry count to reflect that the last
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* entry of the previous table won't be used for
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* linkage. Without this, sg_kfree() may get
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* confused.
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*/
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if (prv)
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table->nents = ++table->orig_nents;
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return -ENOMEM;
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}
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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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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_alloc_table_from_pages - Allocate and initialize an sg table from
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* an array of pages
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* @sgt: The sg table header to use
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* @pages: Pointer to an array of page pointers
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* @n_pages: Number of pages in the pages array
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* @offset: Offset from start of the first page to the start of a buffer
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* @size: Number of valid bytes in the buffer (after offset)
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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 from a list of pages. Contiguous
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* ranges of the pages are squashed into a single scatterlist node. A user
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* may provide an offset at a start and a size of valid data in a buffer
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* specified by the page array. The returned sg table is released by
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* sg_free_table.
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*
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* Returns:
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* 0 on success, negative error on failure
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*/
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int sg_alloc_table_from_pages(struct sg_table *sgt,
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struct page **pages, unsigned int n_pages,
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unsigned long offset, unsigned long size,
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gfp_t gfp_mask)
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{
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unsigned int chunks;
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unsigned int i;
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unsigned int cur_page;
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int ret;
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struct scatterlist *s;
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/* compute number of contiguous chunks */
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chunks = 1;
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for (i = 1; i < n_pages; ++i)
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if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
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++chunks;
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ret = sg_alloc_table(sgt, chunks, gfp_mask);
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if (unlikely(ret))
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return ret;
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/* merging chunks and putting them into the scatterlist */
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cur_page = 0;
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for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
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unsigned long chunk_size;
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unsigned int j;
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/* look for the end of the current chunk */
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for (j = cur_page + 1; j < n_pages; ++j)
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if (page_to_pfn(pages[j]) !=
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page_to_pfn(pages[j - 1]) + 1)
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break;
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chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
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sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
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size -= chunk_size;
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offset = 0;
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cur_page = j;
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}
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return 0;
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}
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EXPORT_SYMBOL(sg_alloc_table_from_pages);
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void __sg_page_iter_start(struct sg_page_iter *piter,
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struct scatterlist *sglist, unsigned int nents,
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unsigned long pgoffset)
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{
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piter->__pg_advance = 0;
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piter->__nents = nents;
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piter->page = NULL;
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piter->sg = sglist;
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piter->sg_pgoffset = pgoffset;
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}
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EXPORT_SYMBOL(__sg_page_iter_start);
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static int sg_page_count(struct scatterlist *sg)
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{
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return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
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}
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bool __sg_page_iter_next(struct sg_page_iter *piter)
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{
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if (!piter->__nents || !piter->sg)
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return false;
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piter->sg_pgoffset += piter->__pg_advance;
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piter->__pg_advance = 1;
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while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
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piter->sg_pgoffset -= sg_page_count(piter->sg);
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piter->sg = sg_next(piter->sg);
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if (!--piter->__nents || !piter->sg)
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return false;
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}
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piter->page = nth_page(sg_page(piter->sg), piter->sg_pgoffset);
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return true;
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}
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EXPORT_SYMBOL(__sg_page_iter_next);
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/**
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* sg_miter_start - start mapping iteration over a sg list
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* @miter: sg mapping iter to be started
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* @sgl: sg list to iterate over
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* @nents: number of sg entries
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*
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* Description:
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* Starts mapping iterator @miter.
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*
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* Context:
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* Don't care.
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*/
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void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
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unsigned int nents, unsigned int flags)
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{
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memset(miter, 0, sizeof(struct sg_mapping_iter));
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__sg_page_iter_start(&miter->piter, sgl, nents, 0);
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WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
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miter->__flags = flags;
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}
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EXPORT_SYMBOL(sg_miter_start);
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/**
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* sg_miter_next - proceed mapping iterator to the next mapping
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* @miter: sg mapping iter to proceed
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*
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* Description:
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* Proceeds @miter to the next mapping. @miter should have been started
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* using sg_miter_start(). On successful return, @miter->page,
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* @miter->addr and @miter->length point to the current mapping.
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*
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* Context:
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* Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled
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* till @miter is stopped. May sleep if !SG_MITER_ATOMIC.
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*
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* Returns:
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* true if @miter contains the next mapping. false if end of sg
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* list is reached.
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*/
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bool sg_miter_next(struct sg_mapping_iter *miter)
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{
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sg_miter_stop(miter);
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/*
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* Get to the next page if necessary.
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* __remaining, __offset is adjusted by sg_miter_stop
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*/
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if (!miter->__remaining) {
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struct scatterlist *sg;
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unsigned long pgoffset;
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if (!__sg_page_iter_next(&miter->piter))
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return false;
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sg = miter->piter.sg;
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pgoffset = miter->piter.sg_pgoffset;
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miter->__offset = pgoffset ? 0 : sg->offset;
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miter->__remaining = sg->offset + sg->length -
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(pgoffset << PAGE_SHIFT) - miter->__offset;
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miter->__remaining = min_t(unsigned long, miter->__remaining,
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PAGE_SIZE - miter->__offset);
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}
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miter->page = miter->piter.page;
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miter->consumed = miter->length = miter->__remaining;
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if (miter->__flags & SG_MITER_ATOMIC)
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miter->addr = kmap_atomic(miter->page) + miter->__offset;
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else
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miter->addr = kmap(miter->page) + miter->__offset;
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return true;
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}
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EXPORT_SYMBOL(sg_miter_next);
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/**
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* sg_miter_stop - stop mapping iteration
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* @miter: sg mapping iter to be stopped
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*
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* Description:
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* Stops mapping iterator @miter. @miter should have been started
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* started using sg_miter_start(). A stopped iteration can be
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* resumed by calling sg_miter_next() on it. This is useful when
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* resources (kmap) need to be released during iteration.
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*
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* Context:
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* Preemption disabled if the SG_MITER_ATOMIC is set. Don't care
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* otherwise.
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*/
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void sg_miter_stop(struct sg_mapping_iter *miter)
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{
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WARN_ON(miter->consumed > miter->length);
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/* drop resources from the last iteration */
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if (miter->addr) {
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miter->__offset += miter->consumed;
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miter->__remaining -= miter->consumed;
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if (miter->__flags & SG_MITER_TO_SG)
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flush_kernel_dcache_page(miter->page);
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if (miter->__flags & SG_MITER_ATOMIC) {
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WARN_ON_ONCE(preemptible());
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kunmap_atomic(miter->addr);
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} else
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kunmap(miter->page);
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miter->page = NULL;
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miter->addr = NULL;
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miter->length = 0;
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miter->consumed = 0;
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}
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}
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EXPORT_SYMBOL(sg_miter_stop);
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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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unsigned int offset = 0;
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struct sg_mapping_iter miter;
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unsigned long flags;
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unsigned int sg_flags = SG_MITER_ATOMIC;
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if (to_buffer)
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sg_flags |= SG_MITER_FROM_SG;
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else
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sg_flags |= SG_MITER_TO_SG;
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sg_miter_start(&miter, sgl, nents, sg_flags);
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local_irq_save(flags);
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while (sg_miter_next(&miter) && offset < buflen) {
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unsigned int len;
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len = min(miter.length, buflen - offset);
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if (to_buffer)
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memcpy(buf + offset, miter.addr, len);
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else
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memcpy(miter.addr, buf + offset, len);
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offset += len;
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}
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sg_miter_stop(&miter);
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local_irq_restore(flags);
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return offset;
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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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