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authorJason Gunthorpe <jgg@mellanox.com>2019-01-04 11:40:21 -0700
committerJason Gunthorpe <jgg@mellanox.com>2019-02-11 15:02:33 -0700
commitd901b2760dc6cd5fbbf2eac31d71d94baa6c4aef (patch)
tree6598a5b011cea1bcdf160c2be9fd4e677d387e2b /lib
parentf368ff188ae4b3ef6f740a15999ea0373261b619 (diff)
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')
-rw-r--r--lib/scatterlist.c26
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