linux-kernel - [PATCH v1 02/15] iov_iter: add helper to test if an iter would use GUP

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Date:   Thu, 11 Apr 2019 17:08:21 -0400
From:   jglisse@...hat.com
To:     linux-kernel@...r.kernel.org
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-mm@...ck.org, John Hubbard <jhubbard@...dia.com>,
        Jan Kara <jack@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Ming Lei <ming.lei@...hat.com>,
        Dave Chinner <david@...morbit.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Matthew Wilcox <willy@...radead.org>
Subject: [PATCH v1 02/15] iov_iter: add helper to test if an iter would use GUP

From: Jérôme Glisse <jglisse@...hat.com>

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@...hat.com>
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-block@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Jan Kara <jack@...e.cz>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Johannes Thumshirn <jthumshirn@...e.de>
Cc: Christoph Hellwig <hch@....de>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Ming Lei <ming.lei@...hat.com>
Cc: Dave Chinner <david@...morbit.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: Matthew Wilcox <willy@...radead.org>
---
 include/linux/uio.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

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.
  *
-- 
2.20.1