linux-kernel - Re: [PATCH 2/2] drm/i915: Fix incorrect error handling in shmem

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Message-ID: <nd2sd2vdwif242wslgkaonuvskawho36bp6j6a4caghauzx6f5@dgkaow5idqxt>
Date: Wed, 20 Aug 2025 16:10:30 -0100
From: Andi Shyti <andi.shyti@...nel.org>
To: 陈涛涛 Taotao Chen <chentaotao@...iglobal.com>
Cc: "jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>, 
	"joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>, "rodrigo.vivi@...el.com" <rodrigo.vivi@...el.com>, 
	"tursulin@...ulin.net" <tursulin@...ulin.net>, "airlied@...il.com" <airlied@...il.com>, 
	"simona@...ll.ch" <simona@...ll.ch>, "oe-lkp@...ts.linux.dev" <oe-lkp@...ts.linux.dev>, 
	"lkp@...el.com" <lkp@...el.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>, "brauner@...nel.org" <brauner@...nel.org>, 
	"oliver.sang@...el.com" <oliver.sang@...el.com>
Subject: Re: [PATCH 2/2] drm/i915: Fix incorrect error handling in
 shmem_pwrite()

Hi Taotao,

On Mon, Aug 11, 2025 at 09:31:00AM +0000, 陈涛涛 Taotao Chen wrote:
> From: Taotao Chen <chentaotao@...iglobal.com>
> 
> shmem_pwrite() currently checks for short writes before negative error
> codes, which can overwrite real errors (e.g., -EFBIG) with -EIO.
> Reorder the checks to return negative errors first, then handle short
> writes.
> 
> Fixes: 048832a3f400 ("drm/i915: Refactor shmem_pwrite() to use kiocb and write_iter")

I don't think we need the Fixes: tag here, in any case we return
an error and -EIO is somehow correct.

With the Fixes removed:

Reviewed-by: Andi Shyti <andi.shyti@...ux.intel.com>

Andi

> Signed-off-by: Taotao Chen <chentaotao@...iglobal.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> index 2b53aad915f5..702532eef207 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> @@ -441,12 +441,12 @@ shmem_pwrite(struct drm_i915_gem_object *obj,
>  	written = file->f_op->write_iter(&kiocb, &iter);
>  	BUG_ON(written == -EIOCBQUEUED);
>  
> -	if (written != size)
> -		return -EIO;
> -
>  	if (written < 0)
>  		return written;
>  
> +	if (written != size)
> +		return -EIO;
> +
>  	return 0;
>  }
>  
> -- 
> 2.34.1