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

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

[Serge E. Hallyn]

>From 6c4eb2ce2849308c4a745ec1f93001e5064a469c Mon Sep 17 00:00:00 2001
From: Serge Hallyn <serge@us.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@us.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);
-- 
1.5.4.3

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

[Andrew Morton]

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

> >From 6c4eb2ce2849308c4a745ec1f93001e5064a469c Mon Sep 17 00:00:00 2001
> From: Serge Hallyn <serge@us.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@us.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);
_

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

[Serge E. Hallyn]

Quoting Andrew Morton (akpm@linux-foundation.org):
> On Wed, 11 Jun 2008 14:37:29 -0500 "Serge E. Hallyn" <serue@us.ibm.com> wrote:
> 
> > >From 6c4eb2ce2849308c4a745ec1f93001e5064a469c Mon Sep 17 00:00:00 2001
> > From: Serge Hallyn <serge@us.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@us.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);
> _

Neat.

-serge