diff options
| author | Daniel Lee <chullee@google.com> | 2025-08-04 23:52:26 -0700 |
|---|---|---|
| committer | Jaegeuk Kim <jaegeuk@kernel.org> | 2025-08-11 17:03:27 +0000 |
| commit | 632f0b6c3e32758e5c93d4e3c2860a3708b9853e (patch) | |
| tree | 9d00826c7f18a06d5f13c55fe77017112d4b1eef /Documentation/filesystems | |
| parent | 76bb6a72bc1daa3d973395349f366231768f8877 (diff) | |
| download | tip-632f0b6c3e32758e5c93d4e3c2860a3708b9853e.tar.gz | |
f2fs: add lookup_mode mount option
For casefolded directories, f2fs may fall back to a linear search if
a hash-based lookup fails. This can cause severe performance
regressions.
While this behavior can be controlled by userspace tools (e.g. mkfs,
fsck) by setting an on-disk flag, a kernel-level solution is needed
to guarantee the lookup behavior regardless of the on-disk state.
This commit introduces the 'lookup_mode' mount option to provide this
kernel-side control.
The option accepts three values:
- perf: (Default) Enforces a hash-only lookup. The linear fallback
is always disabled.
- compat: Enables the linear search fallback for compatibility with
directory entries from older kernels.
- auto: Determines the mode based on the on-disk flag, preserving the
userspace-based behavior.
Signed-off-by: Daniel Lee <chullee@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/f2fs.rst | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst index e5bb89452aff29..5cad369ceb920a 100644 --- a/Documentation/filesystems/f2fs.rst +++ b/Documentation/filesystems/f2fs.rst @@ -370,6 +370,25 @@ errors=%s Specify f2fs behavior on critical errors. This supports modes: ====================== =============== =============== ======== nat_bits Enable nat_bits feature to enhance full/empty nat blocks access, by default it's disabled. +lookup_mode=%s Control the directory lookup behavior for casefolded + directories. This option has no effect on directories + that do not have the casefold feature enabled. + + ================== ======================================== + Value Description + ================== ======================================== + perf (Default) Enforces a hash-only lookup. + The linear search fallback is always + disabled, ignoring the on-disk flag. + compat Enables the linear search fallback for + compatibility with directory entries + created by older kernel that used a + different case-folding algorithm. + This mode ignores the on-disk flag. + auto F2FS determines the mode based on the + on-disk `SB_ENC_NO_COMPAT_FALLBACK_FL` + flag. + ================== ======================================== ======================== ============================================================ Debugfs Entries |