Re: [PATCH 03/20] scripts/make-erofs.sh: Avoid unneeded calls to awk and chmod

[Alyssa Ross <hi@alyssa.is>]

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Demi Marie Obenour <demiobenour@gmail.com> writes:

> These calls were made to work around permission problems, but it is much
> cleaner to solve these problems by making every directory in the new
> filesystem image writable so that cp can write to it.
>
> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
> ---
>  scripts/make-erofs.sh | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/scripts/make-erofs.sh b/scripts/make-erofs.sh
> index 3f211d848b938405510d0dbf6b11cf5512c9ef5d..e63bcbed9c3028f0f2b55431d46ba9ec67bc26ef 100755
> --- a/scripts/make-erofs.sh
> +++ b/scripts/make-erofs.sh
> @@ -37,18 +37,18 @@ while read -r arg1; do
>  	fi
>  	echo
>  
> -	parent="$(dirname "$arg2")"
> -	awk -v parent="$parent" -v root="$root" 'BEGIN {
> -		n = split(parent, components, "/")
> -		for (i = 1; i <= n; i++) {
> -			printf "%s/", root
> -			for (j = 1; j <= i; j++)
> -				printf "%s/", components[j]
> -			print
> -		}
> -	}' | xargs -rd '\n' chmod +w -- 2>/dev/null || :
> -	mkdir -p -- "$root/$parent"
> +	if [ "$arg2" = / ]; then
> +		cp -RT -- "$arg1" "$root"
> +		# Nix store paths are read-only, so fix up permissions
> +		# so that subsequent copies can write to directories
> +		# created by the above copy.  This means giving all
> +		# directories 0755 permissions.
> +		find "$root" -type d -exec chmod 0755 -- '{}' +

Won't this be much slower, since it runs across the whole root every
time?  We're going from one chmod() per path component to one for each
directory in root, aren't we?

> +		continue
> +	fi
>  
> +	parent=$(dirname "$arg2")
> +	mkdir -p -- "$root/$parent"
>  	cp -RT -- "$arg1" "$root/$arg2"
>  done
>  
>
> -- 
> 2.51.0

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