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From:   John Hubbard <jhubbard@nvidia.com>
To:     Andrew Morton <akpm@linux-foundation.org>
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Subject: [PATCH v2 06/18] goldish_pipe: convert to pin_user_pages() and put_user_page()
Date:   Sun, 3 Nov 2019 13:18:01 -0800
Message-ID: <20191103211813.213227-7-jhubbard@nvidia.com>
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1. Call the new global pin_user_pages_fast(), from pin_goldfish_pages().

2. As required by pin_user_pages(), release these pages via
put_user_page(). In this case, do so via put_user_pages_dirty_lock().

That has the side effect of calling set_page_dirty_lock(), instead
of set_page_dirty(). This is probably more accurate.

As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [1]

Another side effect is that the release code is simplified because
the page[] loop is now in gup.c instead of here, so just delete the
local release_user_pages() entirely, and call
put_user_pages_dirty_lock() directly, instead.

[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/platform/goldfish/goldfish_pipe.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/g=
oldfish/goldfish_pipe.c
index 7ed2a21a0bac..635a8bc1b480 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -274,7 +274,7 @@ static int pin_goldfish_pages(unsigned long first_page,
 		*iter_last_page_size =3D last_page_size;
 	}
=20
-	ret =3D get_user_pages_fast(first_page, requested_pages,
+	ret =3D pin_user_pages_fast(first_page, requested_pages,
 				  !is_write ? FOLL_WRITE : 0,
 				  pages);
 	if (ret <=3D 0)
@@ -285,18 +285,6 @@ static int pin_goldfish_pages(unsigned long first_page=
,
 	return ret;
 }
=20
-static void release_user_pages(struct page **pages, int pages_count,
-			       int is_write, s32 consumed_size)
-{
-	int i;
-
-	for (i =3D 0; i < pages_count; i++) {
-		if (!is_write && consumed_size > 0)
-			set_page_dirty(pages[i]);
-		put_page(pages[i]);
-	}
-}
-
 /* Populate the call parameters, merging adjacent pages together */
 static void populate_rw_params(struct page **pages,
 			       int pages_count,
@@ -372,7 +360,8 @@ static int transfer_max_buffers(struct goldfish_pipe *p=
ipe,
=20
 	*consumed_size =3D pipe->command_buffer->rw_params.consumed_size;
=20
-	release_user_pages(pipe->pages, pages_count, is_write, *consumed_size);
+	put_user_pages_dirty_lock(pipe->pages, pages_count,
+				  !is_write && *consumed_size > 0);
=20
 	mutex_unlock(&pipe->lock);
 	return 0;
--=20
2.23.0