Re: [PATCH v2 00/13] f2fs: introduce inline tail

[Chao Yu]

On 2024/9/11 11:57, Wu Bo 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

MKFS_OPTIONS  -- -O extra_attr,encrypt,inode_checksum,flexible_inline_xattr,inode_crtime,verity,compression -f /dev/vdc
MOUNT_OPTIONS -- -o acl,user_xattr -o discard,inline_tail /dev/vdc /mnt/scratch_f2fs

Before:
Failures: generic/042 generic/050 generic/250 generic/252 generic/270 generic/389 generic/563 generic/700 generic/735
Failed 9 of 746 tests

After:
Failures: generic/042 generic/050 generic/125 generic/250 generic/252 generic/270 generic/389 generic/418 generic/551 generic/563 generic/700 generic/735
Failed 12 of 746 tests

Failures: f2fs/004

Can you please check failed testcases?

Thanks,

> ---
> v2:
> - fix ARCH=arc build warning
>
> ---
> 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(-)
>
>
> base-commit: 67784a74e258a467225f0e68335df77acd67b7ab