Re: [PATCH] btrfs: do not allow -o compress-force to override per-inode settings

[Josef Bacik <josef@toxicpanda.com>]

On 11/30/20 9:08 AM, Roman Mamedov wrote:
> On Mon, 30 Nov 2020 08:46:21 -0500
> Josef Bacik <josef@toxicpanda.com> wrote:
> 
>> However some time later we got chattr -c, which is a user way of
>> indicating that the file shouldn't be compressed.  This is at odds with
>> -o compress-force.  We should be honoring what the user wants, which is
>> to disable compression.
> 
> But chattr -c only removes the previously set chattr +c. There's no
> "negative-c" to be forced by user in attributes. And +c is already unset on all
> files by default. Unless I'm missing something? Thanks
> 

The thing you're missing is that when we do chattr -c we're setting NOCOMPRESS 
on the file.  The thing that I'm missing is what exactly we're trying to allow. 
  If chattr -c is supposed to just be the removal of +c, then btrfs is doing the 
wrong thing by setting NOCOMPRESS.  We also do the same thing when we clear a 
btrfs.compression property.

I guess the question is what do we want?  Do we want to only allow the user to 
indicate we want compression, or do we want to allow them to also indicate that 
they don't want compression?  If we don't want to enable them to disable 
compression for a file, then this patch needs to be thrown away, but then we 
also need to fix up all the places we set NOCOMPRESS when we clear these flags. 
  Thanks,

Josef