Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> It can't. Per your latest branch:
Yes it can. Patch 6:
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -282,6 +282,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
if (blk_queue_pci_p2pdma(rq->q))
extract_flags |= ITER_ALLOW_P2PDMA;
+ bio_set_flag(bio, BIO_PAGE_REFFED);
while (iov_iter_count(iter)) {
struct page **pages, *stack_pages[UIO_FASTIOV];
ssize_t bytes;
Patch 7:
+static inline unsigned int bio_to_gup_flags(struct bio *bio)
+{
+ return (bio_flagged(bio, BIO_PAGE_REFFED) ? FOLL_GET : 0) |
+ (bio_flagged(bio, BIO_PAGE_PINNED) ? FOLL_PIN : 0);
+}
+
+/*
+ * Clean up a page appropriately, where the page may be pinned, may have a
+ * ref taken on it or neither.
+ */
+static inline void bio_release_page(struct bio *bio, struct page *page)
+{
+ page_put_unpin(page, bio_to_gup_flags(bio));
+}
At patch 8, you can get either FOLL_GET, FOLL_PIN or 0, depending on the path
you go through.
David
