linux-kernel - Re: [PATCH v3 13/13] bcachefs: fiemap: emit new COMPRESSED state

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Date: Sat, 6 Apr 2024 01:20:46 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Andreas Dilger <adilger@...ger.ca>
Cc: Sweet Tea Dorminy <sweettea-kernel@...miny.me>, 
	Jonathan Corbet <corbet@....net>, Brian Foster <bfoster@...hat.com>, Chris Mason <clm@...com>, 
	Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>, 
	Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
	Mickaël Salaün <mic@...ikod.net>, linux-doc@...r.kernel.org, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-bcachefs@...r.kernel.org, 
	linux-btrfs <linux-btrfs@...r.kernel.org>, linux-f2fs-devel@...ts.sourceforge.net, 
	linux-fsdevel <linux-fsdevel@...r.kernel.org>, kernel-team@...a.com
Subject: Re: [PATCH v3 13/13] bcachefs: fiemap: emit new COMPRESSED state

On Fri, Apr 05, 2024 at 01:17:45PM -0600, Andreas Dilger wrote:
> On Apr 3, 2024, at 1:22 AM, Sweet Tea Dorminy <sweettea-kernel@...miny.me> wrote:
> > 
> > Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@...miny.me>
> > ---
> > fs/bcachefs/fs.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/bcachefs/fs.c b/fs/bcachefs/fs.c
> > index d2793bae842d..54f613f977b4 100644
> > --- a/fs/bcachefs/fs.c
> > +++ b/fs/bcachefs/fs.c
> > @@ -921,7 +921,7 @@ static int bch2_fill_extent(struct bch_fs *c,
> > 				flags2 |= FIEMAP_EXTENT_UNWRITTEN;
> > 
> > 			if (p.crc.compression_type) {
> > -				flags2 |= FIEMAP_EXTENT_ENCODED;
> > +				flags2 |= FIEMAP_EXTENT_DATA_COMPRESSED;
> 
> (defect) This should *also* set FIEMAP_EXTENT_ENCODED in this case,
> along with FIEMAP_EXTENT_DATA_COMPRESSED.  Both for compatibility with
> older code that doesn't understand FIEMAP_EXTENT_DATA_COMPRESSED, and
> because the data still cannot be read directly from the volume when it
> is not mounted.
> 
> Probably Kent should chime in here with what needs to be done to set
> the phys_len properly for bcachefs, or leave this patch out of your
> series and let him submit it directly.  With proposed wrapper in the
> first patch of the series there isn't a hard requirement to change
> all of the filesystems in one shot.

You get phys len from crc.compressed_size - that's always guaranteed,
even if it's not compressed