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From: Roman Mamedov <rm@romanrm.net>
To: Nikolay Borisov <nborisov@suse.com>
Cc: Qu Wenruo <wqu@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH] btrfs: inode: Don't compress if NODATASUM or NODATACOW set
Date: Mon, 14 May 2018 14:39:33 +0500	[thread overview]
Message-ID: <20180514143933.60b3bb76@natsu> (raw)
In-Reply-To: <ea90a7da-a055-6879-e64f-f0f3bca81a23@suse.com>

On Mon, 14 May 2018 11:36:26 +0300
Nikolay Borisov <nborisov@suse.com> wrote:

> So what made you have these expectation, is it codified somewhere
> (docs/man pages etc)? I'm fine with that semantics IF this is what
> people expect.

"Compression ...does not work for NOCOW files":
https://btrfs.wiki.kernel.org/index.php/Compression

The mount options man page does not say that the NOCOW attribute of files will
be disregarded with compress-force.  It only mentions interaction with the
nodatacow and nodatasum mount options. So I'd expect the attribute to still
work and prevent compression of NOCOW files.

> Now the question is why people grew up to have this expectation and not the
> other way round? IMO force_compress should really disregard everything else

Both are knobs that the user needs to explicitly set, the difference is that
the +C attribute is fine-grained and the mount option is global. If they are
set by the user to conflicting values, it seems more useful to have the
fine-grained control override the global one, not the other way round.

-- 
With respect,
Roman

  parent reply	other threads:[~2018-05-14  9:39 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-14  7:02 [PATCH] btrfs: inode: Don't compress if NODATASUM or NODATACOW set Qu Wenruo
2018-05-14  8:10 ` Nikolay Borisov
2018-05-14  8:20   ` Roman Mamedov
2018-05-14  8:36     ` Nikolay Borisov
2018-05-14  9:31       ` james harvey
2018-05-14  9:39       ` Roman Mamedov [this message]
2018-05-14  9:46         ` Nikolay Borisov
2018-05-14 16:49           ` David Sterba
2018-05-14  9:30     ` james harvey
2018-05-14 10:35       ` Qu Wenruo
2018-05-14 22:24         ` james harvey
2018-05-15  0:15         ` james harvey
2018-05-14  8:24   ` Qu Wenruo
2018-05-14 16:52 ` David Sterba
2018-05-14 20:46   ` Timofey Titovets
2018-05-15 18:18     ` David Sterba
2018-05-14 22:29   ` james harvey
2018-05-15  1:35   ` Qu Wenruo

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