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 <chul...@google.com>
---
Documentation/ABI/testing/sysfs-fs-f2fs | 14 ++++++++++++++
fs/f2fs/sysfs.c | 18 ++++++++++++++++++
2 files changed, 32 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs
b/Documentation/ABI/testing/sysfs-fs-f2fs
index bf03263b9f46..e847a50e7403 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -861,3 +861,17 @@ Description: This is a read-only entry to show the
value of sb.s_encoding_flags,
SB_ENC_STRICT_MODE_FL 0x00000001
SB_ENC_NO_COMPAT_FALLBACK_FL 0x00000002
============================ ==========
+
+What: /sys/fs/f2fs/<disk>/effective_lookup_mode
+Date: August 2025
+Contact: "Daniel Lee" <chul...@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
+ for casefolded directories.
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 75134d69a0bd..9897dd8564e0 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -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_get_lookup_mode(sbi)) {
+ 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, "perf\n");
+ return sysfs_emit(buf, "compat\n");
+ }
+ return 0;
+}
+
static ssize_t mounted_time_sec_show(struct f2fs_attr *a,
struct f2fs_sb_info *sbi, char *buf)
{
@@ -1166,6 +1182,7 @@ 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);
@@ -1282,6 +1299,7 @@ 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),
--
2.50.1.565.gc32cd1483b-goog
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