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

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Feb 24, 2026 at 09:36:38AM +0100, Horst Birthelmer wrote:
> 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>

Thanks for the review!

--D