[f2fs-dev] [PATCH] mkfs.f2fs: support -C [no]hashonly to control linear lookup fallback

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

It provides a way to disable linear lookup fallback during mkfs.

Usage:

1. Disable linear lookup:
mkfs.f2fs -f -O casefold -C utf8:hashonly /dev/vdb
dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]

2. Enable linear lookup:
mkfs.f2fs -f -O casefold -C utf8:nohashonly /dev/vdb
dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]

mkfs.f2fs -f -O casefold -C utf8 /dev/vdb
dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]

Signed-off-by: Chao Yu <chao@kernel.org>
---
 lib/libf2fs.c   | 1 +
 man/mkfs.f2fs.8 | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/libf2fs.c b/lib/libf2fs.c
index 2f012c8..0e3e62a 100644
--- a/lib/libf2fs.c
+++ b/lib/libf2fs.c
@@ -1424,6 +1424,7 @@ static const struct enc_flags {
 	char *param;
 } encoding_flags[] = {
 	{ F2FS_ENC_STRICT_MODE_FL, "strict" },
+	{ F2FS_ENC_NO_COMPAT_FALLBACK_FL, "hashonly"}
 };
 
 /* Return a positive number < 0xff indicating the encoding magic number
diff --git a/man/mkfs.f2fs.8 b/man/mkfs.f2fs.8
index 8b3b0cc..b57f033 100644
--- a/man/mkfs.f2fs.8
+++ b/man/mkfs.f2fs.8
@@ -232,10 +232,16 @@ Use UTF-8 for casefolding.
 .I flags:
 .RS 1.2i
 .TP 1.2i
-.B strict
+.B [no]strict
 This flag specifies that invalid strings should be rejected by the filesystem.
 Default is disabled.
 .RE
+.RS 1.2i
+.TP 1.2i
+.B [no]hashonly
+This flag specifies that there is no linear lookup fallback during lookup.
+By default, linear lookup fallback is enabled.
+.RE
 .RE
 .TP
 .BI \-q
-- 
2.49.0



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