linux-kernel - Re: [PATCH] drm/ttm: use swap macro in ttm_bo_handle_move

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Message-ID: <20180713160127.GA14777@vmware.com>
Date:   Fri, 13 Jul 2018 09:01:28 -0700
From:   Sinclair Yeh <syeh@...are.com>
To:     Christian König <christian.koenig@....com>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Roger He <Hongbo.He@....com>, David Airlie <airlied@...ux.ie>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/ttm: use swap macro in ttm_bo_handle_move_mem

On Fri, Jul 13, 2018 at 08:41:37AM +0200, Christian König wrote:
> Am 13.07.2018 um 04:37 schrieb Sinclair Yeh:
> >On Mon, Jul 09, 2018 at 10:24:47AM -0500, Gustavo A. R. Silva wrote:
> >>Make use of the swap macro and remove unnecessary variable *tmp_mem*.
> >>This makes the code easier to read and maintain. Also, reduces the
> >>stack usage.
> >>
> >>This code was detected with the help of Coccinelle.
> >>
> >>Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> >>---
> >>  drivers/gpu/drm/ttm/ttm_bo.c | 7 ++-----
> >>  1 file changed, 2 insertions(+), 5 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> >>index 5d8688e52..5142dcb 100644
> >>--- a/drivers/gpu/drm/ttm/ttm_bo.c
> >>+++ b/drivers/gpu/drm/ttm/ttm_bo.c
> >>@@ -287,12 +287,9 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
> >>  	if (ret) {
> >>  		if (bdev->driver->move_notify) {
> >>-			struct ttm_mem_reg tmp_mem = *mem;
> >>-			*mem = bo->mem;
> >>-			bo->mem = tmp_mem;
> >>+			swap(*mem, bo->mem);
> >>  			bdev->driver->move_notify(bo, false, mem);
> >>-			bo->mem = *mem;
> >>-			*mem = tmp_mem;
> >>+			swap(*mem, bo->mem);
> >This code assumes bo->mem is the same as tmp_mem after the call to
> >move_notify. Is this always true?
> 
> Actually the old code assumed that. Using the swap macro now fixed that
> little unclean implementation.

Ok, thanks for the clarification.  This looks good to me.