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From:   john.hubbard@gmail.com
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Subject: [PATCH v2 32/34] goldfish_pipe: convert put_page() to put_user_page*()
Date:   Sun,  4 Aug 2019 15:49:13 -0700
Message-Id: <20190804224915.28669-33-jhubbard@nvidia.com>
In-Reply-To: <20190804224915.28669-1-jhubbard@nvidia.com>
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From: John Hubbard <jhubbard@nvidia.com>

For pages that were retained via get_user_pages*(), release those pages
via the new put_user_page*() routines, instead of via put_page() or
release_pages().

This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
("mm: introduce put_user_page*(), placeholder versions").

Note that this effectively changes the code's behavior in
qp_release_pages(): it now ultimately calls 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]

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

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Roman Kiryanov <rkir@google.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/platform/goldfish/goldfish_pipe.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
index cef0133aa47a..2bd21020e288 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -288,15 +288,12 @@ static int pin_user_pages(unsigned long first_page,
 static void release_user_pages(struct page **pages, int pages_count,
 			       int is_write, s32 consumed_size)
 {
-	int i;
+	bool dirty = !is_write && consumed_size > 0;
 
-	for (i = 0; i < pages_count; i++) {
-		if (!is_write && consumed_size > 0)
-			set_page_dirty(pages[i]);
-		put_page(pages[i]);
-	}
+	put_user_pages_dirty_lock(pages, pages_count, dirty);
 }
 
+
 /* Populate the call parameters, merging adjacent pages together */
 static void populate_rw_params(struct page **pages,
 			       int pages_count,
-- 
2.22.0