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

From: Chao Yu
Date: Thu Sep 12 2024 - 03:14:32 EST


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