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f2fs: add sysfs entry for effective lookup mode

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This commit introduces a new read-only sysfs entry at
/sys/fs/f2fs/<device>/effective_lookup_mode.

This entry displays the actual directory lookup mode F2FS is
currently using. This is needed for debugging and verification,
as the behavior is determined by both on-disk flags and mount
options.

Signed-off-by: Daniel Lee <chullee@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Daniel Lee 2025-08-04 23:52:27 -07:00 committed by Jaegeuk Kim
parent 632f0b6c3e
commit 1bd119da0b
2 changed files with 33 additions and 0 deletions
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15
Documentation/ABI/testing/sysfs-fs-f2fs
View File

@ -883,3 +883,18 @@ Date: June 2025
Contact: "Daeho Jeong" <daehojeong@google.com>
Description: Control GC algorithm for boost GC. 0: cost benefit, 1: greedy
Default: 1
What: /sys/fs/f2fs/<disk>/effective_lookup_mode
Date: August 2025
Contact: "Daniel Lee" <chullee@google.com>
Description:
This is a read-only entry to show the effective directory lookup mode
F2FS is currently using for casefolded directories.
This considers both the "lookup_mode" mount option and the on-disk
encoding flag, SB_ENC_NO_COMPAT_FALLBACK_FL.
Possible values are:
- "perf": Hash-only lookup.
- "compat": Hash-based lookup with a linear search fallback enabled
- "auto:perf": lookup_mode is auto and fallback is disabled on-disk
- "auto:compat": lookup_mode is auto and fallback is enabled on-disk

18
fs/f2fs/sysfs.c
View File

@ -281,6 +281,22 @@ static ssize_t encoding_flags_show(struct f2fs_attr *a,
le16_to_cpu(F2FS_RAW_SUPER(sbi)->s_encoding_flags));
}
static ssize_t effective_lookup_mode_show(struct f2fs_attr *a,
struct f2fs_sb_info *sbi, char *buf)
{
switch (F2FS_OPTION(sbi).lookup_mode) {
case LOOKUP_PERF:
return sysfs_emit(buf, "perf\n");
case LOOKUP_COMPAT:
return sysfs_emit(buf, "compat\n");
case LOOKUP_AUTO:
if (sb_no_casefold_compat_fallback(sbi->sb))
return sysfs_emit(buf, "auto:perf\n");
return sysfs_emit(buf, "auto:compat\n");
}
return 0;
}
static ssize_t mounted_time_sec_show(struct f2fs_attr *a,
struct f2fs_sb_info *sbi, char *buf)
{
@ -1211,6 +1227,7 @@ F2FS_GENERAL_RO_ATTR(current_reserved_blocks);
F2FS_GENERAL_RO_ATTR(unusable);
F2FS_GENERAL_RO_ATTR(encoding);
F2FS_GENERAL_RO_ATTR(encoding_flags);
F2FS_GENERAL_RO_ATTR(effective_lookup_mode);
F2FS_GENERAL_RO_ATTR(mounted_time_sec);
F2FS_GENERAL_RO_ATTR(main_blkaddr);
F2FS_GENERAL_RO_ATTR(pending_discard);
@ -1329,6 +1346,7 @@ static struct attribute *f2fs_attrs[] = {
ATTR_LIST(current_reserved_blocks),
ATTR_LIST(encoding),
ATTR_LIST(encoding_flags),
ATTR_LIST(effective_lookup_mode),
ATTR_LIST(mounted_time_sec),
#ifdef CONFIG_F2FS_STAT_FS
ATTR_LIST(cp_foreground_calls),