Re: [pve-devel] [PATCH storage 2/2] Storage/Plugin: read .comment files for comments

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

On 12.11.20 16:26, Dominik Csapak wrote:
> we have no way of setting them yet via api, but we can read them now
> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
>  PVE/Storage/Plugin.pm | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 

applied, but dropped the relatively complicated optimizations which avoided
a probably cached stat in an edge case - I do not see much value in such
over optimizations which make a previous simple sub harder to understand
without even noting why it was done anywhere - especially without any stats
providing some hard numbers about if and in what environments this actually
helps.

> diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
> index a046640..00ce9cb 100644
> --- a/PVE/Storage/Plugin.pm
> +++ b/PVE/Storage/Plugin.pm
> @@ -19,6 +19,8 @@ use base qw(PVE::SectionConfig);
>  
>  use constant COMPRESSOR_RE => 'gz|lzo|zst';
>  
> +use constant COMMENT_EXT => ".comment";
> +
>  our @COMMON_TAR_FLAGS = qw(
>      --one-file-system
>      -p --sparse --numeric-owner --acls
> @@ -987,8 +989,18 @@ my $get_subdir_files = sub {
>  
>      my $res = [];
>  
> +    my $has_comment = {};
> +
>      foreach my $fn (<$path/*>) {
>  
> +	if (COMMENT_EXT eq substr($fn, -length(COMMENT_EXT))) {
> +	    my $real_fn = substr($fn, 0, length($fn) -  length(COMMENT_EXT));
> +	    if (!defined($has_comment->{$real_fn})) {
> +		$has_comment->{$real_fn} = (-f $fn);

this is a stat too, so this all only avoided one unused away stat for each
unlikely case that a backup has a comment file.

> +	    }
> +	    next; # we do not need to do anything with comments themselves
> +	}
> +
>  	my $st = File::stat::stat($fn);
>  
>  	next if (!$st || S_ISDIR($st->mode));
> @@ -1008,6 +1020,7 @@ my $get_subdir_files = sub {
>  	} elsif ($tt eq 'backup') {
>  	    next if defined($vmid) && $fn !~  m/\S+-$vmid-\S+/;
>  	    next if $fn !~ m!/([^/]+\.(tgz|(?:(?:tar|vma)(?:\.(${\COMPRESSOR_RE}))?)))$!;
> +	    my $original = $fn;
>  	    my $format = $2;
>  	    $fn = $1;
>  	    $info = { volid => "$sid:backup/$fn", format => $format };
> @@ -1020,6 +1033,16 @@ my $get_subdir_files = sub {
>  		$info->{vmid} = $vmid // $1;
>  	    }
>  
> +	    my $comment_fn = $original.COMMENT_EXT;
> +	    if (!defined($has_comment->{$original})) {
> +		$has_comment->{$original} = (-f $comment_fn);
> +	    }
> +
> +	    if ($has_comment->{$original}) {
> +		my $comment = PVE::Tools::file_read_firstline($comment_fn);
> +		$info->{comment} = $comment if defined($comment);
> +	    }
> +
>  	} elsif ($tt eq 'snippets') {
>  
>  	    $info = {
>