[PATCH] mm/zswap: Add return value in zswap_frontswap_load

[PATCH] mm/zswap: Add return value in zswap_frontswap_load

[Nathan Chancellor]

Clang warns:

mm/zswap.c:1271:6: warning: variable 'ret' is used uninitialized
whenever 'if' condition is true [-Wsometimes-uninitialized]
        if (!entry->length) {
            ^~~~~~~~~~~~~~
mm/zswap.c:1322:9: note: uninitialized use occurs here
        return ret;
               ^~~
mm/zswap.c:1271:2: note: remove the 'if' if its condition is always
false
        if (!entry->length) {
        ^~~~~~~~~~~~~~~~~~~~~
mm/zswap.c:1259:9: note: initialize the variable 'ret' to silence this
warning
        int ret;
               ^
                = 0
1 warning generated.

Prior to "mm/zswap: add the flag can_sleep_mapped", this path always
returned 0. Restore that so we are not returning uninitialized memory.

Link: https://github.com/ClangBuiltLinux/linux/issues/1263
Reported-by: kernelci.org bot <bot@kernelci.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---

Andrew, please fold this into

mm-zswap-add-the-flag-can_sleep_mapped.patch

 mm/zswap.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/zswap.c b/mm/zswap.c
index 6e0bb61d2a2c..a85334b719b9 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1272,6 +1272,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 		dst = kmap_atomic(page);
 		zswap_fill_page(dst, entry->value);
 		kunmap_atomic(dst);
+		ret = 0;
 		goto freeentry;
 	}
 

base-commit: bc085f8fc88fc16796c9f2364e2bfb3fef305cad
-- 
2.30.0

Re: [PATCH] mm/zswap: Add return value in zswap_frontswap_load

[Miaohe Lin]

Hi:
On 2021/1/22 5:48, Nathan Chancellor wrote:
> Clang warns:
> 
> mm/zswap.c:1271:6: warning: variable 'ret' is used uninitialized
> whenever 'if' condition is true [-Wsometimes-uninitialized]
>         if (!entry->length) {
>             ^~~~~~~~~~~~~~
> mm/zswap.c:1322:9: note: uninitialized use occurs here
>         return ret;
>                ^~~
> mm/zswap.c:1271:2: note: remove the 'if' if its condition is always
> false
>         if (!entry->length) {
>         ^~~~~~~~~~~~~~~~~~~~~
> mm/zswap.c:1259:9: note: initialize the variable 'ret' to silence this
> warning
>         int ret;
>                ^
>                 = 0
> 1 warning generated.
> 
> Prior to "mm/zswap: add the flag can_sleep_mapped", this path always
> returned 0. Restore that so we are not returning uninitialized memory.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1263
> Reported-by: kernelci.org bot <bot@kernelci.org>
> Reported-by: kernel test robot <lkp@intel.com>

Looks like commit 6753c561f653 ("mm/zswap: add the flag can_sleep_mapped") introduced this warning.

> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> 
> Andrew, please fold this into
> 
> mm-zswap-add-the-flag-can_sleep_mapped.patch
> 
>  mm/zswap.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 6e0bb61d2a2c..a85334b719b9 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1272,6 +1272,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
>  		dst = kmap_atomic(page);
>  		zswap_fill_page(dst, entry->value);
>  		kunmap_atomic(dst);
> +		ret = 0;
>  		goto freeentry;
>  	}
>  
> 
> base-commit: bc085f8fc88fc16796c9f2364e2bfb3fef305cad
> 

Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>