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From: David Sterba <dsterba@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	Gao Xiang <hsiangkao@linux.alibaba.com>,
	"Darrick J . Wong" <djwong@kernel.org>,
	Huang Jianan <huangjianan@oppo.com>,
	linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Andreas Gruenbacher <andreas.gruenbacher@gmail.com>
Subject: Re: [PATCH v7] iomap: make inline data support more flexible
Date: Tue, 27 Jul 2021 18:53:16 +0200	[thread overview]
Message-ID: <20210727165315.GU5047@suse.cz> (raw)
In-Reply-To: <YQALsvt0UWGW+iMw@casper.infradead.org>

On Tue, Jul 27, 2021 at 02:35:46PM +0100, Matthew Wilcox wrote:
> On Tue, Jul 27, 2021 at 10:20:42AM +0200, David Sterba wrote:
> > On Mon, Jul 26, 2021 at 02:17:02PM +0200, Christoph Hellwig wrote:
> > > > Subject: iomap: Support tail packing
> > > 
> > > I can't say I like this "tail packing" language here when we have the
> > > perfectly fine inline wording.  Same for various comments in the actual
> > > code.
> > 
> > Yes please, don't call it tail-packing when it's an inline extent, we'll
> > use that for btrfs eventually and conflating the two terms has been
> > cofusing users. Except reiserfs, no linux filesystem does tail-packing.
> 
> Hmm ... I see what reiserfs does as packing tails of multiple files into
> one block.  What gfs2 (and ext4) do is inline data.  Erofs packs the
> tail of a single file into the same block as the inode.  If I understand
> what btrfs does correctly, it stores data in the btree.  But (like
> gfs2/ext4), it's only for the entire-file-is-small case, not for
> its-just-ten-bytes-into-the-last-block case.
> 
> So what would you call what erofs is doing if not tail-packing?

That indeed sounds like tail-packing and I was not aware of that, the
docs I found were not clear what exactly was going on with the data
stored inline.

> Wikipedia calls it https://en.wikipedia.org/wiki/Block_suballocation
> which doesn't quite fit.  We need a phrase which means "this isn't
> just for small files but for small tails of large files".

So that's more generic than what we now have as inline files, so in the
interface everybody sets 0 as start of the range while erofs can also
set start of the last partial block.

WARNING: multiple messages have this Message-ID (diff)
From: David Sterba <dsterba@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
	"Darrick J . Wong" <djwong@kernel.org>,
	Andreas Gruenbacher <andreas.gruenbacher@gmail.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-erofs@lists.ozlabs.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v7] iomap: make inline data support more flexible
Date: Tue, 27 Jul 2021 18:53:16 +0200	[thread overview]
Message-ID: <20210727165315.GU5047@suse.cz> (raw)
In-Reply-To: <YQALsvt0UWGW+iMw@casper.infradead.org>

On Tue, Jul 27, 2021 at 02:35:46PM +0100, Matthew Wilcox wrote:
> On Tue, Jul 27, 2021 at 10:20:42AM +0200, David Sterba wrote:
> > On Mon, Jul 26, 2021 at 02:17:02PM +0200, Christoph Hellwig wrote:
> > > > Subject: iomap: Support tail packing
> > > 
> > > I can't say I like this "tail packing" language here when we have the
> > > perfectly fine inline wording.  Same for various comments in the actual
> > > code.
> > 
> > Yes please, don't call it tail-packing when it's an inline extent, we'll
> > use that for btrfs eventually and conflating the two terms has been
> > cofusing users. Except reiserfs, no linux filesystem does tail-packing.
> 
> Hmm ... I see what reiserfs does as packing tails of multiple files into
> one block.  What gfs2 (and ext4) do is inline data.  Erofs packs the
> tail of a single file into the same block as the inode.  If I understand
> what btrfs does correctly, it stores data in the btree.  But (like
> gfs2/ext4), it's only for the entire-file-is-small case, not for
> its-just-ten-bytes-into-the-last-block case.
> 
> So what would you call what erofs is doing if not tail-packing?

That indeed sounds like tail-packing and I was not aware of that, the
docs I found were not clear what exactly was going on with the data
stored inline.

> Wikipedia calls it https://en.wikipedia.org/wiki/Block_suballocation
> which doesn't quite fit.  We need a phrase which means "this isn't
> just for small files but for small tails of large files".

So that's more generic than what we now have as inline files, so in the
interface everybody sets 0 as start of the range while erofs can also
set start of the last partial block.

  parent reply	other threads:[~2021-07-27 16:56 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-23 17:41 [PATCH v7] iomap: make inline data support more flexible Gao Xiang
2021-07-23 17:41 ` Gao Xiang
2021-07-23 19:40 ` Matthew Wilcox
2021-07-23 19:40   ` Matthew Wilcox
2021-07-24  0:54   ` Gao Xiang
2021-07-24  0:54     ` Gao Xiang
2021-07-25 21:39 ` Andreas Grünbacher
2021-07-25 21:39   ` Andreas Grünbacher
2021-07-25 22:16 ` Andreas Gruenbacher
2021-07-25 22:16   ` Andreas Gruenbacher
2021-07-26  2:36   ` Gao Xiang
2021-07-26  2:36     ` Gao Xiang
2021-07-26  7:22     ` Andreas Gruenbacher
2021-07-26  7:22       ` Andreas Gruenbacher
2021-07-26  7:38       ` Gao Xiang
2021-07-26  7:38         ` Gao Xiang
2021-07-26 21:36       ` Darrick J. Wong
2021-07-26 21:36         ` Darrick J. Wong
2021-07-26 22:20         ` Andreas Grünbacher
2021-07-26 22:20           ` Andreas Grünbacher
2021-07-26  3:06   ` Matthew Wilcox
2021-07-26  3:06     ` Matthew Wilcox
2021-07-26  6:56     ` Andreas Gruenbacher
2021-07-26  6:56       ` Andreas Gruenbacher
2021-07-26  4:00   ` Gao Xiang
2021-07-26  4:00     ` Gao Xiang
2021-07-26  8:08     ` Andreas Grünbacher
2021-07-26  8:08       ` Andreas Grünbacher
2021-07-26  8:17       ` Gao Xiang
2021-07-26  8:17         ` Gao Xiang
2021-07-26 11:06     ` Andreas Gruenbacher
2021-07-26 11:06       ` Andreas Gruenbacher
2021-07-26 12:17       ` Christoph Hellwig
2021-07-26 12:17         ` Christoph Hellwig
2021-07-26 12:27         ` Andreas Grünbacher
2021-07-26 12:27           ` Andreas Grünbacher
2021-07-26 12:50           ` Gao Xiang
2021-07-26 12:50             ` Gao Xiang
2021-07-26 13:10             ` Andreas Gruenbacher
2021-07-26 13:27           ` Christoph Hellwig
2021-07-26 13:27             ` Christoph Hellwig
2021-07-27  8:20         ` David Sterba
2021-07-27  8:20           ` David Sterba
2021-07-27 13:35           ` Matthew Wilcox
2021-07-27 15:04             ` Gao Xiang
2021-07-27 15:04               ` Gao Xiang
2021-07-27 16:53             ` David Sterba [this message]
2021-07-27 16:53               ` David Sterba
2021-07-26 12:32       ` Matthew Wilcox
2021-07-26 12:32         ` Matthew Wilcox
2021-07-26 13:03         ` Andreas Gruenbacher
2021-07-26 13:03           ` Andreas Gruenbacher
2021-07-26 13:12           ` Gao Xiang
2021-07-26 13:12             ` Gao Xiang
2021-07-26 13:30             ` Christoph Hellwig
2021-07-26  8:08 ` Joseph Qi
2021-07-26  8:08   ` Joseph Qi
2021-08-01 10:29 Andreas Gruenbacher
2021-08-01 10:29 ` Andreas Gruenbacher

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