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| author | Jason Gunthorpe <jgg@mellanox.com> | 2019-01-04 11:40:21 -0700 |
|---|---|---|
| committer | Jason Gunthorpe <jgg@mellanox.com> | 2019-02-11 15:02:33 -0700 |
| commit | d901b2760dc6cd5fbbf2eac31d71d94baa6c4aef (patch) | |
| tree | 6598a5b011cea1bcdf160c2be9fd4e677d387e2b /lib/scatterlist.c | |
| parent | f368ff188ae4b3ef6f740a15999ea0373261b619 (diff) | |
| download | linux-d901b2760dc6cd5fbbf2eac31d71d94baa6c4aef.tar.bz2 | |
lib/scatterlist: Provide a DMA page iterator
Commit 2db76d7c3c6d ("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>
Diffstat (limited to 'lib/scatterlist.c')
| -rw-r--r-- | lib/scatterlist.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 9ba349e775ef..739dc9fe2c55 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -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 |