On 2020-05-26 12:28, Souptick Joarder wrote:
@@ -486,7 +486,7 @@ static int tce_iommu_use_page(unsigned long tce, unsigned long *hpa) struct page *page = NULL; enum dma_data_direction direction = iommu_tce_direction(tce); - if (get_user_pages_fast(tce & PAGE_MASK, 1, + if (pin_user_pages_fast(tce & PAGE_MASK, 1, direction != DMA_TO_DEVICE ? FOLL_WRITE : 0, &page) != 1) return -EFAULT;There are few places where nr_pages is passed as 1 to get_user_pages_fast(). With similar conversion those will be changed to pin_user_pages_fast(). Does it make sense to add an inline like - pin_user_page_fast(), similar to get_user_page_fast_only() ( now merged in linux-next) ?
Perhaps not *just* yet, IMHO. There are only two places so far: here, and dax_lock_page(). And we don't expect that many places, either, because pin_user_pages*(), unlike get_user_pages(), is more likely to operate on a bunch of pages at once. Although, that could change if we look into the remaining call sites and find more single-page cases that need a gup-to-pup conversion. get_user_pages*() has a few more situations (Case 4, in Documentation/core-api/pin_user_pages.rst: struct page manipulation) in which it operates on single pages. Those will remain get_user_pages*() calls, or perhaps change to get_user_page(). thanks, -- John Hubbard NVIDIA
