Bug 1775790

For kernel builds, /usr/lib/rpm/kmod.prov is fork+execed by rpmbuild in "Processing files:" step about 8000 times, single-threaded, with cumulative run time of ~2 minutes.

Ideally rpmbuild should be changed to parallelize this, but it's not trivial to implement.

I propose meanwhile to speed up the script, by avoiding additional fork+execing.
    Current one:

IFS=$'\n'

for i in $(grep -E '(/lib/modules/.*\.ko|/lib/modules/.*/modules.builtin)');
do
        kmod=$(basename $i | sed -e 's/.[xg]z//');

        if [ $kmod == "modules.builtin" ]; then
                for j in $(cat $i); do
                        j=$(basename $j);
                        echo "kmod($j)"
                done
        else
                echo "kmod($kmod)"
        fi
done

    Proposed replacement:

IFS=$'\n'

read -r fname || exit

# Only process files from .../lib/modules/... subtree
[ "${fname#*/lib/modules/*}" != "$fname" ] || exit 0

kmod=${fname##*/}  # like basename, but faster

if [ "$kmod" = "modules.builtin" ]; then
        for j in $(cat -- "$fname"); do
                echo "kmod(${j##*/})"
        done
        exit 0
fi

kmod=${kmod%.gz}
kmod=${kmod%.xz}
if [ "${kmod%.ko}" != "$kmod" ]; then
        echo "kmod($kmod)"
fi


Tested to work, observed speedup: almost exactly 2 times faster.

While verifying correctness, noticed that old script was buggy - it was generating a bogus "Provides:" item - kmod(modules.builtin.modinfo),
because the logic in script was filtering for */*.ko files and for */modules.builtin* files, and wasn't prepared for the existence of */modules.builtin.modinfo file.