Re: [PATCH 2/5] fuse: quiet down complaints in fuse_conn_limit_write

[Horst Birthelmer <horst@birthelmer.de>]

On Mon, Feb 23, 2026 at 03:06:50PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> gcc 15 complains about an uninitialized variable val that is passed by
> reference into fuse_conn_limit_write:
> 
>  control.c: In function ‘fuse_conn_congestion_threshold_write’:
>  include/asm-generic/rwonce.h:55:37: warning: ‘val’ may be used uninitialized [-Wmaybe-uninitialized]
>     55 |         *(volatile typeof(x) *)&(x) = (val);                            \
>        |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
>  include/asm-generic/rwonce.h:61:9: note: in expansion of macro ‘__WRITE_ONCE’
>     61 |         __WRITE_ONCE(x, val);                                           \
>        |         ^~~~~~~~~~~~
>  control.c:178:9: note: in expansion of macro ‘WRITE_ONCE’
>    178 |         WRITE_ONCE(fc->congestion_threshold, val);
>        |         ^~~~~~~~~~
>  control.c:166:18: note: ‘val’ was declared here
>    166 |         unsigned val;
>        |                  ^~~
> 
> Unfortunately there's enough macro spew involved in kstrtoul_from_user
> that I think gcc gives up on its analysis and sprays the above warning.
> AFAICT it's not actually a bug, but we could just zero-initialize the
> variable to enable using -Wmaybe-uninitialized to find real problems.
> 
> Previously we would use some weird uninitialized_var annotation to quiet
> down the warnings, so clearly this code has been like this for quite
> some time.
> 
> Cc: <stable@vger.kernel.org> # v5.9
> Fixes: 3f649ab728cda8 ("treewide: Remove uninitialized_var() usage")
> Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
> ---
>  fs/fuse/control.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> 
> diff --git a/fs/fuse/control.c b/fs/fuse/control.c
> index 140bd5730d9984..073c2d8e4dfc7c 100644
> --- a/fs/fuse/control.c
> +++ b/fs/fuse/control.c
> @@ -121,7 +121,7 @@ static ssize_t fuse_conn_max_background_write(struct file *file,
>  					      const char __user *buf,
>  					      size_t count, loff_t *ppos)
>  {
> -	unsigned val;
> +	unsigned val = 0;
>  	ssize_t ret;
>  
>  	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
> @@ -163,7 +163,7 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
>  						    const char __user *buf,
>  						    size_t count, loff_t *ppos)
>  {
> -	unsigned val;
> +	unsigned val = 0;
>  	struct fuse_conn *fc;
>  	ssize_t ret;
>  
> 
> 

This looks good to me. Trivial fix for an annoying problem.
Reviewed-by: Horst Birthelmer <hbirthelmer@ddn.com>