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| author | Jason Gunthorpe <jgg@nvidia.com> | 2020-10-16 08:46:01 -0300 |
|---|---|---|
| committer | Jason Gunthorpe <jgg@nvidia.com> | 2020-10-16 12:41:33 -0300 |
| commit | 9a40401cfa1356b0d169be8470ed7b2edc33b98f (patch) | |
| tree | d5a06663aaea0288eacc183ac2d41ef785191987 /lib | |
| parent | 16e7483e6f02973972f832b18042fd6c45fe26c0 (diff) | |
| download | lwn-9a40401cfa1356b0d169be8470ed7b2edc33b98f.tar.gz lwn-9a40401cfa1356b0d169be8470ed7b2edc33b98f.zip | |
lib/scatterlist: Do not limit max_segment to PAGE_ALIGNED values
The main intention of the max_segment argument to
__sg_alloc_table_from_pages() is to match the DMA layer segment size set
by dma_set_max_seg_size().
Restricting the input to be page aligned makes it impossible to just
connect the DMA layer to this API.
The only reason for a page alignment here is because the algorithm will
overshoot the max_segment if it is not a multiple of PAGE_SIZE. Simply fix
the alignment before starting and don't expose this implementation detail
to the callers.
A future patch will completely remove SCATTERLIST_MAX_SEGMENT.
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/scatterlist.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c index e102fdfaa75b..ed2497c79a21 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -404,7 +404,7 @@ static struct scatterlist *get_next_sg(struct sg_table *table, * @n_pages: Number of pages in the pages array * @offset: Offset from start of the first page to the start of a buffer * @size: Number of valid bytes in the buffer (after offset) - * @max_segment: Maximum size of a scatterlist node in bytes (page aligned) + * @max_segment: Maximum size of a scatterlist element in bytes * @prv: Last populated sge in sgt * @left_pages: Left pages caller have to set after this call * @gfp_mask: GFP allocation mask @@ -435,7 +435,12 @@ struct scatterlist *__sg_alloc_table_from_pages(struct sg_table *sgt, unsigned int added_nents = 0; struct scatterlist *s = prv; - if (WARN_ON(!max_segment || offset_in_page(max_segment))) + /* + * The algorithm below requires max_segment to be aligned to PAGE_SIZE + * otherwise it can overshoot. + */ + max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE); + if (WARN_ON(max_segment < PAGE_SIZE)) return ERR_PTR(-EINVAL); if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && prv) @@ -542,8 +547,7 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages, unsigned long size, gfp_t gfp_mask) { return PTR_ERR_OR_ZERO(__sg_alloc_table_from_pages(sgt, pages, n_pages, - offset, size, SCATTERLIST_MAX_SEGMENT, - NULL, 0, gfp_mask)); + offset, size, UINT_MAX, NULL, 0, gfp_mask)); } EXPORT_SYMBOL(sg_alloc_table_from_pages); |