From 0db9299f48ebd4a860d6ad4e1d36ac50671d48e7 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 30 Nov 2007 09:16:50 +0100 Subject: 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 --- include/linux/scatterlist.h | 125 +++++++++----------------------------------- 1 file changed, 25 insertions(+), 100 deletions(-) (limited to 'include/linux') diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index e3ff21dbac53..e9cb103417b2 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -7,6 +7,12 @@ #include #include +struct sg_table { + struct scatterlist *sgl; /* the list */ + unsigned int nents; /* number of mapped entries */ + unsigned int orig_nents; /* original size of list */ +}; + /* * Notes on SG table design. * @@ -106,71 +112,12 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf, sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); } -/** - * sg_next - return the next scatterlist entry in a list - * @sg: The current sg entry - * - * 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) -{ -#ifdef CONFIG_DEBUG_SG - BUG_ON(sg->sg_magic != SG_MAGIC); -#endif - if (sg_is_last(sg)) - return NULL; - - sg++; - if (unlikely(sg_is_chain(sg))) - sg = sg_chain_ptr(sg); - - return sg; -} - /* * Loop over each sg element, following the pointer to a new list if necessary */ #define for_each_sg(sglist, sg, nr, __i) \ for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) -/** - * sg_last - return the last scatterlist entry in a list - * @sgl: First entry in the scatterlist - * @nents: Number of entries in the scatterlist - * - * 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@. - * - **/ -static inline struct scatterlist *sg_last(struct scatterlist *sgl, - unsigned int nents) -{ -#ifndef ARCH_HAS_SG_CHAIN - struct scatterlist *ret = &sgl[nents - 1]; -#else - struct scatterlist *sg, *ret = NULL; - unsigned int i; - - 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; -} - /** * sg_chain - Chain two sglists together * @prv: First scatterlist @@ -222,47 +169,6 @@ static inline void sg_mark_end(struct scatterlist *sg) sg->page_link &= ~0x01; } -/** - * 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); -#ifdef CONFIG_DEBUG_SG - { - unsigned int i; - for (i = 0; i < nents; i++) - sgl[i].sg_magic = SG_MAGIC; - } -#endif - sg_mark_end(&sgl[nents - 1]); -} - -/** - * 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) -{ - sg_init_table(sg, 1); - sg_set_buf(sg, buf, buflen); -} - /** * sg_phys - Return physical address of an sg entry * @sg: SG entry @@ -293,4 +199,23 @@ static inline void *sg_virt(struct scatterlist *sg) return page_address(sg_page(sg)) + sg->offset; } +struct scatterlist *sg_next(struct scatterlist *); +struct scatterlist *sg_last(struct scatterlist *s, unsigned int); +void sg_init_table(struct scatterlist *, unsigned int); +void sg_init_one(struct scatterlist *, const void *, unsigned int); + +typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); +typedef void (sg_free_fn)(struct scatterlist *, unsigned int); + +void __sg_free_table(struct sg_table *, sg_free_fn *); +void sg_free_table(struct sg_table *); +int __sg_alloc_table(struct sg_table *, unsigned int, gfp_t, sg_alloc_fn *); +int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); + +/* + * Maximum number of entries that will be allocated in one piece, if + * a list larger than this is required then chaining will be utilized. + */ +#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist)) + #endif /* _LINUX_SCATTERLIST_H */ -- cgit v1.2.2 From 7cedb1f17fb7f4374d11501f61656ae9d3ba47e9 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Sun, 13 Jan 2008 14:15:28 -0600 Subject: SG: work with the SCSI fixed maximum allocations. SCSI sg table allocation has a maximum size (of SCSI_MAX_SG_SEGMENTS, currently 128) and this will cause a BUG_ON() in SCSI if something tries an allocation over it. This patch adds a size limit to the chaining allocator to allow the specification of the maximum allocation size for chaining, so we always chain in units of the maximum SCSI allocation size. Signed-off-by: James Bottomley Signed-off-by: Jens Axboe --- include/linux/scatterlist.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index e9cb103417b2..a3d567a974e8 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -207,9 +207,10 @@ void sg_init_one(struct scatterlist *, const void *, unsigned int); typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); typedef void (sg_free_fn)(struct scatterlist *, unsigned int); -void __sg_free_table(struct sg_table *, sg_free_fn *); +void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *); void sg_free_table(struct sg_table *); -int __sg_alloc_table(struct sg_table *, unsigned int, gfp_t, sg_alloc_fn *); +int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t, + sg_alloc_fn *); int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); /* -- cgit v1.2.2