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

[Eric Biggers]

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?

- Eric