On Tue, Oct 01, 2019 at 11:32:50AM -0700, Alan Mikhak wrote: > From: Alan Mikhak <[email protected]> > > Update the description of sg_set_page() to communicate current > requirements for the page pointer parameter. > > Signed-off-by: Alan Mikhak <[email protected]> > include/linux/scatterlist.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index 6eec50fb36c8..6dda865893aa 100644 > +++ b/include/linux/scatterlist.h > @@ -112,6 +112,12 @@ static inline void sg_assign_page(struct scatterlist > *sg, struct page *page) > * of the page pointer. See sg_page() for looking up the page belonging > * to an sg entry. > * > + * Scatterlist currently expects the page parameter to be a pointer to > + * a page that is backed by a page struct. > + * > + * Page pointers derived from addresses obtained from ioremap() are > + * currently not supported since they require use of iomem safe memcpy. > + * > **/ > static inline void sg_set_page(struct scatterlist *sg, struct page *page, > unsigned int len, unsigned int offset)
It seems a bit weird to have a comment explaining that 'struct page *page' must actually be a valid pointer. Of course it must. Computing a 'struct page *' to something that doesn't actually have a struct page is simply a bug in whoever did that. Code should never be interchanging ioremap results with the struct page* world. Jason
