linux-kernel - [PATCH v5 12/15] /dev/mem: Only set filp->f

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Date:   Fri, 30 Oct 2020 11:08:12 +0100
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-media@...r.kernel.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kees Cook <keescook@...omium.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        John Hubbard <jhubbard@...dia.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jan Kara <jack@...e.cz>
Subject: [PATCH v5 12/15] /dev/mem: Only set filp->f_mapping

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@...el.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: Kees Cook <keescook@...omium.org>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Jérôme Glisse <jglisse@...hat.com>
Cc: Jan Kara <jack@...e.cz>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: linux-mm@...ck.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-samsung-soc@...r.kernel.org
Cc: linux-media@...r.kernel.org
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
---
 drivers/char/mem.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 94c2b556cf97..7dcf9e4ea79d 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;
-- 
2.28.0