[PATCH] swapfile.c: Initialize a variable.

[PATCH] swapfile.c: Initialize a variable.

[Il Han]

Initialize the variable to remove the following warning.

mm/swapfile.c:2028: warning: 'span' may be used uninitialized in this function

Initialize it.

Signed-off-by: Il Han <corone.il.han@gmail.com>
---
 mm/swapfile.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 17bc224..d5ca685 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2016,7 +2016,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int error;
 	union swap_header *swap_header;
 	int nr_extents;
-	sector_t span;
+	sector_t span = 0;
 	unsigned long maxpages;
 	unsigned char *swap_map = NULL;
 	struct page *page = NULL;
-- 
1.7.4.1

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Re: [PATCH] swapfile.c: Initialize a variable.

[Michal Hocko]

On Thu 06-10-11 13:41:14, Il Han wrote:
> Initialize the variable to remove the following warning.
> 
> mm/swapfile.c:2028: warning: 'span' may be used uninitialized in this function
> 
> Initialize it.

It looks that the warning is bogus because span is always initialized
if nr_extents >=0. Check out setup_swap_map_and_extents and
setup_swap_extents (for S_ISBLK it is trivial and for S_ISREG we are
setting the value after we jump out of the loop and all error cases go
either to out directly or through bad_bmap labels).

It should be much better to use uninitialized_var instead if we just
want to shut up compiler.

> 
> Signed-off-by: Il Han <corone.il.han@gmail.com>
> ---
>  mm/swapfile.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 17bc224..d5ca685 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2016,7 +2016,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
>  	int error;
>  	union swap_header *swap_header;
>  	int nr_extents;
> -	sector_t span;
> +	sector_t span = 0;
>  	unsigned long maxpages;
>  	unsigned char *swap_map = NULL;
>  	struct page *page = NULL;
> -- 
> 1.7.4.1
> 
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> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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