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lib/scatterlist: Add support in dynamic allocation of SG table from pages

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Extend __sg_alloc_table_from_pages to support dynamic allocation of
SG table from pages. It should be used by drivers that can't supply
all the pages at one time.

This function returns the last populated SGE in the table. Users should
pass it as an argument to the function from the second call and forward.
As before, nents will be equal to the number of populated SGEs (chunks).

With this new extension, drivers can benefit the optimization of merging
contiguous pages without a need to allocate all pages in advance and
hold them in a large buffer.

E.g. with the Infiniband driver that allocates a single page for hold the
pages. For 1TB memory registration, the temporary buffer would consume only
4KB, instead of 2GB.

Link: https://lore.kernel.org/r/20201004154340.1080481-2-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Maor Gottlieb
2020-10-04 18:43:37 +03:00
committed by Jason Gunthorpe
parent 29d88681fb
commit 07da1223ec
5 changed files with 142 additions and 57 deletions
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38
include/linux/scatterlist.h
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@@ -165,6 +165,22 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
#define for_each_sgtable_dma_sg(sgt, sg, i) \
for_each_sg((sgt)->sgl, sg, (sgt)->nents, i)
static inline void __sg_chain(struct scatterlist *chain_sg,
struct scatterlist *sgl)
{
/*
* offset and length are unused for chain entry. Clear them.
*/
chain_sg->offset = 0;
chain_sg->length = 0;
/*
* Set lowest bit to indicate a link pointer, and make sure to clear
* the termination bit if it happens to be set.
*/
chain_sg->page_link = ((unsigned long) sgl | SG_CHAIN) & ~SG_END;
}
/**
* sg_chain - Chain two sglists together
* @prv: First scatterlist
@@ -178,18 +194,7 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
struct scatterlist *sgl)
{
/*
* offset and length are unused for chain entry. Clear them.
*/
prv[prv_nents - 1].offset = 0;
prv[prv_nents - 1].length = 0;
/*
* Set lowest bit to indicate a link pointer, and make sure to clear
* the termination bit if it happens to be set.
*/
prv[prv_nents - 1].page_link = ((unsigned long) sgl | SG_CHAIN)
& ~SG_END;
__sg_chain(&prv[prv_nents - 1], sgl);
}
/**
@@ -286,10 +291,11 @@ void sg_free_table(struct sg_table *);
int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
unsigned int n_pages, unsigned int offset,
unsigned long size, unsigned int max_segment,
gfp_t gfp_mask);
struct scatterlist *__sg_alloc_table_from_pages(struct sg_table *sgt,
struct page **pages, unsigned int n_pages, unsigned int offset,
unsigned long size, unsigned int max_segment,
struct scatterlist *prv, unsigned int left_pages,
gfp_t gfp_mask);
int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
unsigned int n_pages, unsigned int offset,
unsigned long size, gfp_t gfp_mask);