Re: [f2fs-dev] [PATCH 00/13] f2fs: introduce inline tail

[Wu Bo]

On Tue, Sep 03, 2024 at 09:29:30AM -0700, Eric Biggers via Linux-f2fs-devel wrote:
> On Tue, Sep 03, 2024 at 02:54:44AM -0600, Wu Bo via Linux-f2fs-devel wrote:
> > The inode in F2FS occupies an entire 4k block. For many small files, this means
> > they consume much more space than their actual size. Therefore, there is
> > significant potential to better utilize the inode block space.
> > 
> > Currently, F2FS has two features to make use of the inode block space: inline
> > data and inline xattr.
> > 
> > Inline data stores file which size is smaller then 3.5k in inode block. However,
> > for slightly larger small files, there still have much waste.
> > For example, a 5k file requires 3 blocks, totaling 12k of space, which is
> > more than twice the size of the file itself!
> > 
> > Additionally, the end of a file often does not occupy an entire block. If we can
> > store the end of the file data within the inode block, we can save an entire
> > block for the file. This is particularly important for small files.
> > 
> > In fact, the current inline data is a special case of inline tail, and
> > inline tail is an extension of inline data.
> > 
> > To make it simple, inline tail only on small files(<64k). And for larger files,
> > inline tails don't provide any significant benefits.
> > 
> > The layout of an inline tail inode block is following:
> > 
> > | inode block     | 4096 |     inline tail enable    |
> > | --------------- | ---- | --------------------------|
> > | inode info      | 360  |                           |
> > | --------------- | ---- | --------------------------|
> > |                 |      | extra info         | 0~36 |
> > |                 |      | **compact_addr[16] | 64   |
> > | addr table[923] | 3692 | reserved           | 4    |
> > |                 |      | **tail data        |      |
> > |                 |      | inline_xattr       | 200  |
> > | --------------- | ---- | --------------------------|
> > | nid table[5]    | 20   |
> > | node footer     | 24   |
> > 
> > F2fs-tools to support inline tail:
> > https://lore.kernel.org/linux-f2fs-devel/20240903075931.3339584-1-bo.wu@xxxxxxxx
> > 
> > I tested inline tail by copying the source code of Linux 6.9.7. The storage
> > space was reduced by approximately 8%. Additionally, due to the reduced IO, the
> > copy time also reduced by around 10%.
> > 
> > This patch series has been tested with xfstests by running 'kvm-xfstests -c f2fs
> > -g quick' both with and without the patch; no regressions were observed.
> > The test result is:
> > f2fs/default: 583 tests, 6 failures, 213 skipped, 650 seconds
> >   Failures: generic/050 generic/064 generic/250 generic/252 generic/563
> >       generic/735
> >       Totals: 607 tests, 213 skipped, 30 failures, 0 errors, 579s
> > 
> > Wu Bo (13):
> >   f2fs: add inline tail mount option
> >   f2fs: add inline tail disk layout definition
> >   f2fs: implement inline tail write & truncate
> >   f2fs: implement inline tail read & fiemap
> >   f2fs: set inline tail flag when create inode
> >   f2fs: fix address info has been truncated
> >   f2fs: support seek for inline tail
> >   f2fs: convert inline tail when inode expand
> >   f2fs: fix data loss during inline tail writing
> >   f2fs: avoid inlining quota files
> >   f2fs: fix inline tail data lost
> >   f2fs: convert inline tails to avoid potential issues
> >   f2fs: implement inline tail forward recovery
> > 
> >  fs/f2fs/data.c     |  93 +++++++++++++++++++++++++-
> >  fs/f2fs/f2fs.h     |  46 ++++++++++++-
> >  fs/f2fs/file.c     |  85 +++++++++++++++++++++++-
> >  fs/f2fs/inline.c   | 159 +++++++++++++++++++++++++++++++++++++++------
> >  fs/f2fs/inode.c    |   6 ++
> >  fs/f2fs/namei.c    |   3 +
> >  fs/f2fs/node.c     |   6 +-
> >  fs/f2fs/recovery.c |   9 ++-
> >  fs/f2fs/super.c    |  25 +++++++
> >  fs/f2fs/verity.c   |   4 ++
> >  10 files changed, 409 insertions(+), 27 deletions(-)
> 
> This is disabled on encrypted files, right?

Yes, conditions for enabling inline tail are the same as for inline
data now.

Thanks
> 
> - Eric
> 
> 
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