iov_iter: add helper to test if an iter would use GUP

Add an helper to test if call to iov_iter_get_pages*() with a given
iter would result in calls to GUP (get_user_pages*()). We want to
track differently page reference if they are coming from GUP and thus
we need to know when GUP is use for a given iter.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-block@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Matthew Wilcox <willy@infradead.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/uio.h b/include/linux/uio.h
index f184af1999a8..b12b2878a266 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -98,6 +98,17 @@ static inline bool iov_iter_bvec_no_ref(const struct iov_iter *i)
 	return (i->type & ITER_BVEC_FLAG_NO_REF) != 0;
 }
 
+/**
+ * iov_iter_get_pages_use_gup - true if iov_iter_get_pages(i) use GUP
+ * @i: iter
+ * Returns: true if a call to iov_iter_get_pages*() with the iter provided in
+ *          argument would result in the use of get_user_pages*()
+ */
+static inline bool iov_iter_get_pages_use_gup(const struct iov_iter *i)
+{
+	return iov_iter_type(i) & (ITER_IOVEC | ITER_PIPE);
+}
+
 /*
  * Total number of bytes covered by an iovec.
  *