Re: [PATCH 4/4] generic/775: Fix an infinite loop due to variable name clash

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

On Sun, Apr 05, 2026 at 07:37:08PM +0530, Ojaswin Mujoo wrote:
> On Wed, Apr 01, 2026 at 07:32:18AM -0700, Darrick J. Wong wrote:
> > On Wed, Apr 01, 2026 at 04:10:50PM +0530, Ojaswin Mujoo wrote:
> > > We use i as the iteration variable in the main test loop as well as some
> > > internal loops. Due to this clash, $i variable of main test loops was
> > > getting modified by the following loop in prep_mixed_mapping().
> > > 
> > > 	for ((i=0; i<num_blocks; i++)); do
> > > 
> > > If num_blocks is less than 10 (example ext4 with blocksize 4k and
> > > cluster size 8k) i would always be set as 3 and the main loop would
> > > never exit. Take the simplest approach of just renaming the variable.
> > > 
> > > Reported-by: Disha Goel <disgoel@linux.ibm.com>
> > > Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> > > ---
> > >  tests/generic/775 | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/tests/generic/775 b/tests/generic/775
> > > index 2a4287bb..19ae95e2 100755
> > > --- a/tests/generic/775
> > > +++ b/tests/generic/775
> > > @@ -41,7 +41,7 @@ prep_mixed_mapping() {
> > >  
> > >  	local operations=("W" "H" "U")
> > >  	local num_blocks=$((awu_max / blksz))
> > > -	for ((i=0; i<num_blocks; i++)); do
> > > +	for ((j=0; j<num_blocks; j++)); do
> > 
> > You're right that the single-letter variables are a really bad idea in
> > languages like bash/python/etc where functions can see variables in
> > caller's scope if they're not explicitly marked local.
> > 
> > But a) why not use "local i" to prevent that; and (b) if you're going
> > to rename it, why not "blkno"?
> 
> Hey Darrick thanks for the review.
> 
> Why not both a) and b) :).
> I probably shouldve done that in the first place. I'll fix in v2

Yeah, that works! :)

Thanks for making those fixes.

--D

> Thanks,
> ojaswin
> 
> > 
> > --D
> > 
> > >  		local index=$((RANDOM % ${#operations[@]}))
> > >  		local map="${operations[$index]}"
> > >  		local mapping="${mapping}${map}"
> > > -- 
> > > 2.53.0
> > > 
> > > 
>