linux-kernel - Re: [PATCH -mm] mm/shmem.c: ret can be used uninitialized

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Date:	Wed, 11 Jun 2008 18:24:05 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm] mm/shmem.c: ret can be used uninitialized

On Wed, 11 Jun 2008 14:37:29 -0500 "Serge E. Hallyn" <serue@...ibm.com> wrote:

> >From 6c4eb2ce2849308c4a745ec1f93001e5064a469c Mon Sep 17 00:00:00 2001
> From: Serge Hallyn <serge@...ibm.com>
> Date: Wed, 11 Jun 2008 11:20:28 -0500
> Subject: [PATCH -mm] mm/shmem.c: ret can be used uninitialized
> 
> Make sure ret is defined before check at line 1408.
> 
> Signed-off-by: Serge Hallyn <serge@...ibm.com>
> ---
>  mm/shmem.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index ad24be7..b326ff2 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1365,7 +1365,7 @@ repeat:
>  		}
>  
>  		if (!filepage) {
> -			int ret;
> +			int ret = 0;
>  
>  			spin_unlock(&info->lock);
>  			filepage = shmem_alloc_page(gfp, info, idx);

Well yes.  But it adds more text and uncommentedly adds an unnecessary
initialisation.

With a wee bit of thought we can _reduce_ the amount of text and not
add unnecessary stuff?

--- a/mm/shmem.c~memcg-remove-refcnt-from-page_cgroup-fix-2
+++ a/mm/shmem.c
@@ -1396,7 +1396,8 @@ repeat:
 				swap = *entry;
 				shmem_swp_unmap(entry);
 			}
-			if (error || swap.val)
+			ret = error || swap.val;
+			if (ret)
 				mem_cgroup_uncharge_cache_page(filepage);
 			else
 				ret = add_to_page_cache_lru(filepage, mapping,
@@ -1405,7 +1406,7 @@ repeat:
 			 * At add_to_page_cache_lru() failure, uncharge will
 			 * be done automatically.
 			 */
-			if (error || swap.val || ret) {
+			if (ret) {
 				spin_unlock(&info->lock);
 				page_cache_release(filepage);
 				shmem_unacct_blocks(info->flags, 1);
_

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