From 82f66fbef58de4ad7519708d0b9e685e20fa4e8a Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 22 Oct 2007 17:07:37 +0200 Subject: [SG] Add helpers for manipulating SG entries We can then transition drivers without changing the generated code. Signed-off-by: Jens Axboe --- include/linux/scatterlist.h | 112 ++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 104 insertions(+), 8 deletions(-) (limited to 'include/linux') diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 2dc7464cce5..1645795cbb1 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -2,24 +2,37 @@ #define _LINUX_SCATTERLIST_H #include +#include #include #include +/** + * sg_set_page - Set sg entry to point at given page + * @sg: SG entry + * @page: The page + * + * Description: + * Use this function to set an sg entry pointing at a page, never assign + * the page directly. We encode sg table information in the lower bits + * of the page pointer. See sg_page() for looking up the page belonging + * to an sg entry. + * + **/ +static inline void sg_set_page(struct scatterlist *sg, struct page *page) +{ + sg->page = page; +} + +#define sg_page(sg) ((sg)->page) + static inline void sg_set_buf(struct scatterlist *sg, const void *buf, unsigned int buflen) { - sg->page = virt_to_page(buf); + sg_set_page(sg, virt_to_page(buf)); sg->offset = offset_in_page(buf); sg->length = buflen; } -static inline void sg_init_one(struct scatterlist *sg, const void *buf, - unsigned int buflen) -{ - memset(sg, 0, sizeof(*sg)); - sg_set_buf(sg, buf, buflen); -} - /* * We overload the LSB of the page pointer to indicate whether it's * a valid sg entry, or whether it points to the start of a new scatterlist. @@ -104,4 +117,87 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, prv[prv_nents - 1].page = (struct page *) ((unsigned long) sgl | 0x01); } +/** + * sg_mark_end - Mark the end of the scatterlist + * @sgl: Scatterlist + * @nents: Number of entries in sgl + * + * Description: + * Marks the last entry as the termination point for sg_next() + * + **/ +static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents) +{ +} + +static inline void __sg_mark_end(struct scatterlist *sg) +{ +} + + +/** + * sg_init_one - Initialize a single entry sg list + * @sg: SG entry + * @buf: Virtual address for IO + * @buflen: IO length + * + * Notes: + * This should not be used on a single entry that is part of a larger + * table. Use sg_init_table() for that. + * + **/ +static inline void sg_init_one(struct scatterlist *sg, const void *buf, + unsigned int buflen) +{ + memset(sg, 0, sizeof(*sg)); + sg_mark_end(sg, 1); + sg_set_buf(sg, buf, buflen); +} + +/** + * sg_init_table - Initialize SG table + * @sgl: The SG table + * @nents: Number of entries in table + * + * Notes: + * If this is part of a chained sg table, sg_mark_end() should be + * used only on the last table part. + * + **/ +static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) +{ + memset(sgl, 0, sizeof(*sgl) * nents); + sg_mark_end(sgl, nents); +} + +/** + * sg_phys - Return physical address of an sg entry + * @sg: SG entry + * + * Description: + * This calls page_to_phys() on the page in this sg entry, and adds the + * sg offset. The caller must know that it is legal to call page_to_phys() + * on the sg page. + * + **/ +static inline unsigned long sg_phys(struct scatterlist *sg) +{ + return page_to_phys(sg_page(sg)) + sg->offset; +} + +/** + * sg_virt - Return virtual address of an sg entry + * @sg: SG entry + * + * Description: + * This calls page_address() on the page in this sg entry, and adds the + * sg offset. The caller must know that the sg page has a valid virtual + * mapping. + * + **/ +static inline void *sg_virt(struct scatterlist *sg) +{ + return page_address(sg_page(sg)) + sg->offset; +} + #endif /* _LINUX_SCATTERLIST_H */ -- cgit v1.2.3 From 18dabf473e15850c0dbc8ff13ac1e2806d542c15 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 22 Oct 2007 19:57:20 +0200 Subject: Change table chaining layout Change the page member of the scatterlist structure to be an unsigned long, and encode more stuff in the lower bits: - Bits 0 and 1 zero: this is a normal sg entry. Next sg entry is located at sg + 1. - Bit 0 set: this is a chain entry, the next real entry is at ->page_link with the two low bits masked off. - Bit 1 set: this is the final entry in the sg entry. sg_next() will return NULL when passed such an entry. It's thus important that sg table users use the proper accessors to get and set the page member. Signed-off-by: Jens Axboe --- include/linux/scatterlist.h | 78 +++++++++++++++++++++++++++++++-------------- 1 file changed, 54 insertions(+), 24 deletions(-) (limited to 'include/linux') diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 1645795cbb1..c6136e8a7f5 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -2,9 +2,26 @@ #define _LINUX_SCATTERLIST_H #include -#include #include #include +#include + +/* + * Notes on SG table design. + * + * Architectures must provide an unsigned long page_link field in the + * scatterlist struct. We use that to place the page pointer AND encode + * information about the sg table as well. The two lower bits are reserved + * for this information. + * + * If bit 0 is set, then the page_link contains a pointer to the next sg + * table list. Otherwise the next entry is at sg + 1. + * + * If bit 1 is set, then this sg entry is the last element in a list. + * + * See sg_next(). + * + */ /** * sg_set_page - Set sg entry to point at given page @@ -20,11 +37,20 @@ **/ static inline void sg_set_page(struct scatterlist *sg, struct page *page) { - sg->page = page; + unsigned long page_link = sg->page_link & 0x3; + + sg->page_link = page_link | (unsigned long) page; } -#define sg_page(sg) ((sg)->page) +#define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3)) +/** + * sg_set_buf - Set sg entry to point at given data + * @sg: SG entry + * @buf: Data + * @buflen: Data length + * + **/ static inline void sg_set_buf(struct scatterlist *sg, const void *buf, unsigned int buflen) { @@ -38,26 +64,27 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf, * a valid sg entry, or whether it points to the start of a new scatterlist. * Those low bits are there for everyone! (thanks mason :-) */ -#define sg_is_chain(sg) ((unsigned long) (sg)->page & 0x01) +#define sg_is_chain(sg) ((sg)->page_link & 0x01) +#define sg_is_last(sg) ((sg)->page_link & 0x02) #define sg_chain_ptr(sg) \ - ((struct scatterlist *) ((unsigned long) (sg)->page & ~0x01)) + ((struct scatterlist *) ((sg)->page_link & ~0x03)) /** * sg_next - return the next scatterlist entry in a list * @sg: The current sg entry * - * Usually the next entry will be @sg@ + 1, but if this sg element is part - * of a chained scatterlist, it could jump to the start of a new - * scatterlist array. - * - * Note that the caller must ensure that there are further entries after - * the current entry, this function will NOT return NULL for an end-of-list. + * Description: + * Usually the next entry will be @sg@ + 1, but if this sg element is part + * of a chained scatterlist, it could jump to the start of a new + * scatterlist array. * - */ + **/ static inline struct scatterlist *sg_next(struct scatterlist *sg) { - sg++; + if (sg_is_last(sg)) + return NULL; + sg++; if (unlikely(sg_is_chain(sg))) sg = sg_chain_ptr(sg); @@ -75,14 +102,15 @@ static inline struct scatterlist *sg_next(struct scatterlist *sg) * @sgl: First entry in the scatterlist * @nents: Number of entries in the scatterlist * - * Should only be used casually, it (currently) scan the entire list - * to get the last entry. + * Description: + * Should only be used casually, it (currently) scan the entire list + * to get the last entry. * - * Note that the @sgl@ pointer passed in need not be the first one, - * the important bit is that @nents@ denotes the number of entries that - * exist from @sgl@. + * Note that the @sgl@ pointer passed in need not be the first one, + * the important bit is that @nents@ denotes the number of entries that + * exist from @sgl@. * - */ + **/ static inline struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) { @@ -105,16 +133,17 @@ static inline struct scatterlist *sg_last(struct scatterlist *sgl, * @prv_nents: Number of entries in prv * @sgl: Second scatterlist * - * Links @prv@ and @sgl@ together, to form a longer scatterlist. + * Description: + * Links @prv@ and @sgl@ together, to form a longer scatterlist. * - */ + **/ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, struct scatterlist *sgl) { #ifndef ARCH_HAS_SG_CHAIN BUG(); #endif - prv[prv_nents - 1].page = (struct page *) ((unsigned long) sgl | 0x01); + prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01; } /** @@ -128,13 +157,14 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, **/ static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents) { + sgl[nents - 1].page_link = 0x02; } static inline void __sg_mark_end(struct scatterlist *sg) { + sg->page_link |= 0x02; } - /** * sg_init_one - Initialize a single entry sg list * @sg: SG entry @@ -187,7 +217,7 @@ static inline unsigned long sg_phys(struct scatterlist *sg) /** * sg_virt - Return virtual address of an sg entry - * @sg: SG entry + * @sg: SG entry * * Description: * This calls page_address() on the page in this sg entry, and adds the -- cgit v1.2.3 From d6ec084200c37683278c821338f74ddf21ab80f5 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 22 Oct 2007 20:01:06 +0200 Subject: Add CONFIG_DEBUG_SG sg validation Add a Kconfig entry which will toggle some sanity checks on the sg entry and tables. Signed-off-by: Jens Axboe --- include/linux/scatterlist.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'include/linux') diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index c6136e8a7f5..42daf5e1526 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -23,6 +23,8 @@ * */ +#define SG_MAGIC 0x87654321 + /** * sg_set_page - Set sg entry to point at given page * @sg: SG entry @@ -39,6 +41,9 @@ static inline void sg_set_page(struct scatterlist *sg, struct page *page) { unsigned long page_link = sg->page_link & 0x3; +#ifdef CONFIG_DEBUG_SG + BUG_ON(sg->sg_magic != SG_MAGIC); +#endif sg->page_link = page_link | (unsigned long) page; } @@ -81,6 +86,9 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf, **/ static inline struct scatterlist *sg_next(struct scatterlist *sg) { +#ifdef CONFIG_DEBUG_SG + BUG_ON(sg->sg_magic != SG_MAGIC); +#endif if (sg_is_last(sg)) return NULL; @@ -123,6 +131,10 @@ static inline struct scatterlist *sg_last(struct scatterlist *sgl, for_each_sg(sgl, sg, nents, i) ret = sg; +#endif +#ifdef CONFIG_DEBUG_SG + BUG_ON(sgl[0].sg_magic != SG_MAGIC); + BUG_ON(!sg_is_last(ret)); #endif return ret; } @@ -180,6 +192,9 @@ static inline void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) { memset(sg, 0, sizeof(*sg)); +#ifdef CONFIG_DEBUG_SG + sg->sg_magic = SG_MAGIC; +#endif sg_mark_end(sg, 1); sg_set_buf(sg, buf, buflen); } @@ -198,6 +213,13 @@ static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) { memset(sgl, 0, sizeof(*sgl) * nents); sg_mark_end(sgl, nents); +#ifdef CONFIG_DEBUG_SG + { + int i; + for (i = 0; i < nents; i++) + sgl[i].sg_magic = SG_MAGIC; + } +#endif } /** -- cgit v1.2.3