de26103de5
Suggested by Boaz Harrosh <bharrosh@panasas.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
261 lines
6.3 KiB
C
261 lines
6.3 KiB
C
#ifndef _LINUX_SCATTERLIST_H
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#define _LINUX_SCATTERLIST_H
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#include <asm/scatterlist.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <asm/io.h>
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/*
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* Notes on SG table design.
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*
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* Architectures must provide an unsigned long page_link field in the
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* scatterlist struct. We use that to place the page pointer AND encode
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* information about the sg table as well. The two lower bits are reserved
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* for this information.
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*
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* If bit 0 is set, then the page_link contains a pointer to the next sg
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* table list. Otherwise the next entry is at sg + 1.
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*
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* If bit 1 is set, then this sg entry is the last element in a list.
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*
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* See sg_next().
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*
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*/
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#define SG_MAGIC 0x87654321
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/**
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* sg_set_page - Set sg entry to point at given page
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* @sg: SG entry
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* @page: The page
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*
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* Description:
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* Use this function to set an sg entry pointing at a page, never assign
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* the page directly. We encode sg table information in the lower bits
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* of the page pointer. See sg_page() for looking up the page belonging
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* to an sg entry.
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*
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**/
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static inline void sg_set_page(struct scatterlist *sg, struct page *page)
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{
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unsigned long page_link = sg->page_link & 0x3;
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/*
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* In order for the low bit stealing approach to work, pages
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* must be aligned at a 32-bit boundary as a minimum.
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*/
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BUG_ON((unsigned long) page & 0x03);
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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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sg->page_link = page_link | (unsigned long) page;
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}
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#define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3))
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/**
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* sg_set_buf - Set sg entry to point at given data
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* @sg: SG entry
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* @buf: Data
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* @buflen: Data length
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*
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**/
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static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
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unsigned int buflen)
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{
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sg_set_page(sg, virt_to_page(buf));
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sg->offset = offset_in_page(buf);
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sg->length = buflen;
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}
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/*
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* We overload the LSB of the page pointer to indicate whether it's
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* a valid sg entry, or whether it points to the start of a new scatterlist.
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* Those low bits are there for everyone! (thanks mason :-)
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*/
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#define sg_is_chain(sg) ((sg)->page_link & 0x01)
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#define sg_is_last(sg) ((sg)->page_link & 0x02)
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#define sg_chain_ptr(sg) \
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((struct scatterlist *) ((sg)->page_link & ~0x03))
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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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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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* @prv_nents: Number of entries in prv
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* @sgl: Second scatterlist
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*
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* Description:
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* Links @prv@ and @sgl@ together, to form a longer scatterlist.
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*
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**/
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static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
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struct scatterlist *sgl)
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{
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#ifndef ARCH_HAS_SG_CHAIN
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BUG();
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#endif
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prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01;
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}
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/**
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* sg_mark_end - Mark the end of the scatterlist
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* @sgl: Scatterlist
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* @nents: Number of entries in sgl
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*
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* Description:
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* Marks the last entry as the termination point for sg_next()
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*
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**/
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static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents)
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{
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sgl[nents - 1].page_link = 0x02;
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}
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static inline void __sg_mark_end(struct scatterlist *sg)
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{
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sg->page_link |= 0x02;
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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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memset(sg, 0, sizeof(*sg));
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#ifdef CONFIG_DEBUG_SG
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sg->sg_magic = SG_MAGIC;
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#endif
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sg_mark_end(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_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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sg_mark_end(sgl, nents);
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#ifdef CONFIG_DEBUG_SG
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{
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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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}
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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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*
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* Description:
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* This calls page_to_phys() on the page in this sg entry, and adds the
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* sg offset. The caller must know that it is legal to call page_to_phys()
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* on the sg page.
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*
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**/
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static inline unsigned long sg_phys(struct scatterlist *sg)
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{
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return page_to_phys(sg_page(sg)) + sg->offset;
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}
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/**
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* sg_virt - Return virtual address of an sg entry
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* @sg: SG entry
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*
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* Description:
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* This calls page_address() on the page in this sg entry, and adds the
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* sg offset. The caller must know that the sg page has a valid virtual
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* mapping.
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*
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**/
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static inline void *sg_virt(struct scatterlist *sg)
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{
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return page_address(sg_page(sg)) + sg->offset;
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}
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#endif /* _LINUX_SCATTERLIST_H */
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