From 0fb1b1ed7dd92ca9775f8292cc7b85b93182dcb0 Mon Sep 17 00:00:00 2001
From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Fri, 27 Nov 2020 17:41:23 +0100
Subject: [PATCH] /dev/mem: Only set filp->f_mapping
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When we care about pagecache maintenance, we need to make sure that
both f_mapping and i_mapping point at the right mapping.

But for iomem mappings we only care about the virtual/pte side of
things, so f_mapping is enough. Also setting inode->i_mapping was
confusing me as a driver maintainer, since in e.g. drivers/gpu we
don't do that. Per Dan this seems to be copypasta from places which do
care about pagecache consistency, but not needed. Hence remove it for
slightly less confusion.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201127164131.2244124-10-daniel.vetter@ffwll.ch
---
 drivers/char/mem.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 94c2b556cf972..7dcf9e4ea79d0 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -891,7 +891,6 @@ static int open_port(struct inode *inode, struct file *filp)
 	 * revocations when drivers want to take over a /dev/mem mapped
 	 * range.
 	 */
-	inode->i_mapping = devmem_inode->i_mapping;
 	filp->f_mapping = inode->i_mapping;
 
 	return 0;
-- 
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