lib/scatterlist: Provide a DMA page iterator

Commit 2db76d7c3c ("lib/scatterlist: sg_page_iter: support sg lists w/o
backing pages") introduced the sg_page_iter_dma_address() function without
providing a way to use it in the general case. If the sg_dma_len() is not
equal to the sg length callers cannot safely use the
for_each_sg_page/sg_page_iter_dma_address combination.

Resolve this API mistake by providing a DMA specific iterator,
for_each_sg_dma_page(), that uses the right length so
sg_page_iter_dma_address() works as expected with all sglists.

A new iterator type is introduced to provide compile-time safety against
wrongly mixing accessors and iterators.

Acked-by: Christoph Hellwig <hch@lst.de> (for scatterlist)
Acked-by: Thomas Hellstrom <thellstrom@vmware.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> (ipu3-cio2)
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2019-01-04 11:40:21 -07:00
parent f368ff188a
commit d901b2760d
5 changed files with 76 additions and 12 deletions

View File

@ -240,6 +240,7 @@ ForEachMacros:
- 'for_each_set_bit'
- 'for_each_set_bit_from'
- 'for_each_sg'
- 'for_each_sg_dma_page'
- 'for_each_sg_page'
- 'for_each_sibling_event'
- '__for_each_thread'

View File

@ -311,7 +311,13 @@ static dma_addr_t __vmw_piter_dma_addr(struct vmw_piter *viter)
static dma_addr_t __vmw_piter_sg_addr(struct vmw_piter *viter)
{
return sg_page_iter_dma_address(&viter->iter);
/*
* FIXME: This driver wrongly mixes DMA and CPU SG list iteration and
* needs revision. See
* https://lore.kernel.org/lkml/20190104223531.GA1705@ziepe.ca/
*/
return sg_page_iter_dma_address(
container_of(&viter->iter, struct sg_dma_page_iter, base));
}

View File

@ -846,7 +846,7 @@ static int cio2_vb2_buf_init(struct vb2_buffer *vb)
unsigned int pages = DIV_ROUND_UP(vb->planes[0].length, CIO2_PAGE_SIZE);
unsigned int lops = DIV_ROUND_UP(pages + 1, entries_per_page);
struct sg_table *sg;
struct sg_page_iter sg_iter;
struct sg_dma_page_iter sg_iter;
int i, j;
if (lops <= 0 || lops > CIO2_MAX_LOPS) {
@ -873,7 +873,7 @@ static int cio2_vb2_buf_init(struct vb2_buffer *vb)
b->offset = sg->sgl->offset;
i = j = 0;
for_each_sg_page(sg->sgl, &sg_iter, sg->nents, 0) {
for_each_sg_dma_page (sg->sgl, &sg_iter, sg->nents, 0) {
if (!pages--)
break;
b->lop[i][j] = sg_page_iter_dma_address(&sg_iter) >> PAGE_SHIFT;

View File

@ -339,12 +339,12 @@ int sg_alloc_table_chained(struct sg_table *table, int nents,
/*
* sg page iterator
*
* Iterates over sg entries page-by-page. On each successful iteration,
* you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
* to get the current page and its dma address. @piter->sg will point to the
* sg holding this page and @piter->sg_pgoffset to the page's page offset
* within the sg. The iteration will stop either when a maximum number of sg
* entries was reached or a terminating sg (sg_last(sg) == true) was reached.
* Iterates over sg entries page-by-page. On each successful iteration, you
* can call sg_page_iter_page(@piter) to get the current page and its dma
* address. @piter->sg will point to the sg holding this page and
* @piter->sg_pgoffset to the page's page offset within the sg. The iteration
* will stop either when a maximum number of sg entries was reached or a
* terminating sg (sg_last(sg) == true) was reached.
*/
struct sg_page_iter {
struct scatterlist *sg; /* sg holding the page */
@ -356,7 +356,19 @@ struct sg_page_iter {
* next step */
};
/*
* sg page iterator for DMA addresses
*
* This is the same as sg_page_iter however you can call
* sg_page_iter_dma_address(@dma_iter) to get the page's DMA
* address. sg_page_iter_page() cannot be called on this iterator.
*/
struct sg_dma_page_iter {
struct sg_page_iter base;
};
bool __sg_page_iter_next(struct sg_page_iter *piter);
bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter);
void __sg_page_iter_start(struct sg_page_iter *piter,
struct scatterlist *sglist, unsigned int nents,
unsigned long pgoffset);
@ -372,11 +384,13 @@ static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
/**
* sg_page_iter_dma_address - get the dma address of the current page held by
* the page iterator.
* @piter: page iterator holding the page
* @dma_iter: page iterator holding the page
*/
static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
static inline dma_addr_t
sg_page_iter_dma_address(struct sg_dma_page_iter *dma_iter)
{
return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
return sg_dma_address(dma_iter->base.sg) +
(dma_iter->base.sg_pgoffset << PAGE_SHIFT);
}
/**
@ -385,11 +399,28 @@ static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
* @piter: page iterator to hold current page, sg, sg_pgoffset
* @nents: maximum number of sg entries to iterate over
* @pgoffset: starting page offset
*
* Callers may use sg_page_iter_page() to get each page pointer.
*/
#define for_each_sg_page(sglist, piter, nents, pgoffset) \
for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
__sg_page_iter_next(piter);)
/**
* for_each_sg_dma_page - iterate over the pages of the given sg list
* @sglist: sglist to iterate over
* @dma_iter: page iterator to hold current page
* @dma_nents: maximum number of sg entries to iterate over, this is the value
* returned from dma_map_sg
* @pgoffset: starting page offset
*
* Callers may use sg_page_iter_dma_address() to get each page's DMA address.
*/
#define for_each_sg_dma_page(sglist, dma_iter, dma_nents, pgoffset) \
for (__sg_page_iter_start(&(dma_iter)->base, sglist, dma_nents, \
pgoffset); \
__sg_page_iter_dma_next(dma_iter);)
/*
* Mapping sg iterator
*

View File

@ -625,6 +625,32 @@ bool __sg_page_iter_next(struct sg_page_iter *piter)
}
EXPORT_SYMBOL(__sg_page_iter_next);
static int sg_dma_page_count(struct scatterlist *sg)
{
return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT;
}
bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter)
{
struct sg_page_iter *piter = &dma_iter->base;
if (!piter->__nents || !piter->sg)
return false;
piter->sg_pgoffset += piter->__pg_advance;
piter->__pg_advance = 1;
while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) {
piter->sg_pgoffset -= sg_dma_page_count(piter->sg);
piter->sg = sg_next(piter->sg);
if (!--piter->__nents || !piter->sg)
return false;
}
return true;
}
EXPORT_SYMBOL(__sg_page_iter_dma_next);
/**
* sg_miter_start - start mapping iteration over a sg list
* @miter: sg mapping iter to be started