Re: [PATCH 2/3] libmultipath: pgcmp(): compare number of paths

[Benjamin Marzinski <bmarzins@redhat.com>]

On Mon, Nov 25, 2024 at 03:32:23PM +0100, Martin Wilck wrote:
> pathcmp() makes sure that all paths in pgp have a match in cpgp, but not
> vice-versa. Check the number of paths, too.

This looks fine. But looking at it made we a nervous about cpgp->id.  We
only calculate that in pgcmp() (and just for mpp, not cmpp) and in
disassemble_map(). But we clearly can have pathgroup changes after that,
as the last patch has shown. To be safe, we should either skip the whole
pgp->id thing (it's not a huge time savings) or recalculate it for all
of cmpp's path groups before we start the loops in pgcmp().

-Ben

> 
> Fixes: 90773ba ("libmultipath: resolve hash collisions in pgcmp()")
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> ---
>  libmultipath/configure.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/libmultipath/configure.c b/libmultipath/configure.c
> index d0e9c95..55140d0 100644
> --- a/libmultipath/configure.c
> +++ b/libmultipath/configure.c
> @@ -442,6 +442,7 @@ pgcmp (struct multipath * mpp, struct multipath * cmpp)
>  
>  		vector_foreach_slot (cmpp->pg, cpgp, j) {
>  			if (pgp->id == cpgp->id &&
> +			    VECTOR_SIZE(pgp->paths) == VECTOR_SIZE(cpgp->paths) &&
>  			    !pathcmp(pgp, cpgp)) {
>  				r = 0;
>  				break;
> -- 
> 2.47.0