SG: Move functions to lib/scatterlist.c and add sg chaining allocator helpers
Manually doing chained sg lists is not trivial, so add some helpers to make sure that drivers get it right. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe
parent
91525300ba
commit
0db9299f48
3 changed files with 307 additions and 101 deletions
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@ -7,6 +7,12 @@
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#include <linux/string.h>
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#include <asm/io.h>
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struct sg_table {
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struct scatterlist *sgl; /* the list */
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unsigned int nents; /* number of mapped entries */
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unsigned int orig_nents; /* original size of list */
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};
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/*
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* Notes on SG table design.
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*
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@ -106,71 +112,12 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
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sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
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}
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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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static inline 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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/*
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* Loop over each sg element, following the pointer to a new list if necessary
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*/
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#define for_each_sg(sglist, sg, nr, __i) \
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for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
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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) scan 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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static inline struct scatterlist *sg_last(struct scatterlist *sgl,
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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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/**
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* sg_chain - Chain two sglists together
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* @prv: First scatterlist
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@ -222,47 +169,6 @@ static inline void sg_mark_end(struct scatterlist *sg)
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sg->page_link &= ~0x01;
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}
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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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static inline 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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/**
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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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* Notes:
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* This should not be used on a single entry that is part of a larger
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* table. Use sg_init_table() for that.
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*
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**/
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static inline void sg_init_one(struct scatterlist *sg, const void *buf,
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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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/**
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* sg_phys - Return physical address of an sg entry
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* @sg: SG entry
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@ -293,4 +199,23 @@ static inline void *sg_virt(struct scatterlist *sg)
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return page_address(sg_page(sg)) + sg->offset;
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}
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struct scatterlist *sg_next(struct scatterlist *);
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struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
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void sg_init_table(struct scatterlist *, unsigned int);
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void sg_init_one(struct scatterlist *, const void *, unsigned int);
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typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
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typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
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void __sg_free_table(struct sg_table *, sg_free_fn *);
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void sg_free_table(struct sg_table *);
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int __sg_alloc_table(struct sg_table *, unsigned int, gfp_t, sg_alloc_fn *);
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int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
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/*
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* Maximum number of entries that will be allocated in one piece, if
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* a list larger than this is required then chaining will be utilized.
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*/
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#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
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#endif /* _LINUX_SCATTERLIST_H */
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@ -6,7 +6,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
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rbtree.o radix-tree.o dump_stack.o \
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idr.o int_sqrt.o extable.o prio_tree.o \
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sha1.o irq_regs.o reciprocal_div.o argv_split.o \
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proportions.o prio_heap.o
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proportions.o prio_heap.o scatterlist.o
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lib-$(CONFIG_MMU) += ioremap.o
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lib-$(CONFIG_SMP) += cpumask.o
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281
lib/scatterlist.c
Normal file
281
lib/scatterlist.c
Normal file
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@ -0,0 +1,281 @@
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/*
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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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/**
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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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* @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 __sg_alloc_table().
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*
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**/
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void __sg_free_table(struct sg_table *table, 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 SG_MAX_SINGLE_ALLOC 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 > SG_MAX_SINGLE_ALLOC) {
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next = sg_chain_ptr(&sgl[SG_MAX_SINGLE_ALLOC - 1]);
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alloc_size = SG_MAX_SINGLE_ALLOC;
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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_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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* @gfp_mask: GFP allocation mask
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* @alloc_fn: Allocator to use
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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, 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 > SG_MAX_SINGLE_ALLOC);
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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 > SG_MAX_SINGLE_ALLOC) {
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alloc_size = SG_MAX_SINGLE_ALLOC;
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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, SG_MAX_SINGLE_ALLOC, 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, gfp_mask, sg_kmalloc);
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if (unlikely(ret))
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__sg_free_table(table, 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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