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

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, $i variable of main test loops was
> > getting modified by the following loop in prep_mixed_mapping().
> > 
> > 	for ((i=0; i<num_blocks; i++)); do
> > 
> > If num_blocks is less than 10 (example ext4 with blocksize 4k and
> > cluster size 8k) i would always be set as 3 and the main loop would
> > never exit. Take the simplest approach of just renaming the variable.
> > 
> > Reported-by: Disha Goel <[email protected]>
> > Signed-off-by: Ojaswin Mujoo <[email protected]>
> > ---
> >  tests/generic/775 | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tests/generic/775 b/tests/generic/775
> > index 2a4287bb..19ae95e2 100755
> > --- a/tests/generic/775
> > +++ b/tests/generic/775
> > @@ -41,7 +41,7 @@ prep_mixed_mapping() {
> >  
> >  	local operations=("W" "H" "U")
> >  	local num_blocks=$((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

Thanks,
ojaswin

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